Essays on the Intellectual Powers of Man

THOMAS REID

(1710-1796)

Contents

HOW TO READ THE TEXT

Preface

Essay 1: Preliminary

Essay 2: The Powers we have by means of our External senses

Essay 3: Memory

Essay 4: Conception

Essay 5: Abstraction

Essay 6: Judgment

Essay 7: Reasoning

© Jonathan Bennett 2017

Essays on the Intellectual Powers of Man

THOMAS REID

1785

Early Modern Texts, 2017

COPYRIGHT

Essays on the Intellectual Powers of Man

© Jonathan Bennett, 2017. All rights reserved.

Early Modern Texts

First launched: April 2006

Last amended: May 2008

Contact: earlymodern31@gmail.com

www.earlymoderntexts.com

HOW TO READ THE TEXT

[Brackets] enclose editorial explanations. Small ·dots· enclose material that has been added, but can be read as though it were part of the original text. Occasional •bullets, and also indenting of passages that are not quotations, are meant as aids to grasping the structure of a sentence or a thought. Every four-point ellipsis. . . . indicates the omission of a brief passage that seems to present more difficulty than it is worth. Longer omissions are reported between brackets in normal-sized type.

Preface

Human knowledge falls into two parts, one relating to body (material things), the other relating to mind (intellectual things).

The whole system of bodies in the universe, of which we know only a very small part, can be called ‘the material world’; the whole system of minds, from the infinite creator right down to the lowest creature endowed with thought, can be called ‘the intellectual world’. These are the two great kingdoms of Nature that come to our attention; and every art, every science, and every human thought is engaged with one or other of them or with things pertaining to them—the boldest flight of imagination can’t take us outside them.

Even within them there are many things—concerning the nature and the structure of bodies and of minds—that we aren’t equipped to discover, many problems that the ablest philosopher can’t solve; but if there are any natures other than those of body and mind we have no knowledge at all of them, no conception at all of them. [Throughout this work, ‘philosophy’ stands for what you and I call ‘philosophy’ and/or for what we would call ‘science’; the reference of ‘philosopher’ is correspondingly variable.]

Every existing thing must be either •corporeal or •incorporeal—that is obvious. But it isn’t so obvious that every existing thing must be either •corporeal or •endowed with thought. Does the universe contain beings that are neither extended, solid and inert, like body, nor active and thinking, like mind? The answer to that seems to be beyond our reach. There appears to be a vast gulf between body and mind, and we just don’t know whether there is any intermediate nature—·some kind of thing that isn’t either body or mind, but has some points of resemblance with each·—that connects them with one another.

We have no reason to credit plants with thought, or even sensation; yet they display an active force and energy that can’t be ·purely· the result of any arrangement or combination of inert matter. The same thing can be said of the powers by which

animals are nourished and grow,

matter gravitates,

magnetic and electrical bodies attract and repel each other,

the parts of solid bodies hang together.

·There’s no evidence that there is anything thoughtful about any of these, but they seem to involve forces that can’t be explained in terms of what is purely corporeal, i.e. in terms of collisions of inert, inactive material particles·.

Some thinkers have conjectured that all events in the material world that require active force are produced by the continual operation of thinking beings. Others have conjectured that the universe may contain beings that are active but don’t think—a kind of incorporeal machinery (·incorporeal because active·) that God has devised to do their assigned work without any knowledge or intention. We should set aside conjectures, and all claims to settle things that are really beyond our reach, and accept this: the only things we can have any knowledge of, or can form any conception of, are body and mind. . . .

Because all our knowledge is confined to •body and •mind, or things pertaining to them, there are correspondingly two great branches of philosophy. (1) The properties of body, and the laws that hold in the material system, are studied by •natural philosophy, as that word (·i.e. the word ‘natural’·) is now used. (2) The branch that deals with the nature and workings of minds is called •‘pneumatology’ by some, ·though that label won’t occur again in this set of Essays·. The principles of all the sciences belong to one or other of these branches.

We aren’t in a position to say what varieties of minds or thinking beings this vast universe contains. We live in a little corner of God’s dominion, cut off from the rest of it. The globe that we inhabit is merely one of seven planets that encircle our sun.

What kinds of beings inhabit the other six planets, their satellites, and the comets belonging to our system? How many other suns are there that have similar planetary systems? The answers to these questions are entirely hidden from us. Although human reason and hard work have discovered with great accuracy the order and distances of the planets, and the laws governing their motion, we have no way of causally interacting with them.

It’s quite probable that they are inhabited by living creatures, but we know absolutely nothing about the nature or the powers of any such things. Everyone is conscious of a •thinking principle or •mind, in himself, and we have good enough evidence of something similar in other men. [Reid here uses ‘principle’ in a sense that it had in his day, meaning a source. Here, as in many places, it is a cause or active source, so that ‘a thinking principle or mind’ means ‘a thought-generator, i.e. a mind’. Reid also uses ‘principle’ to stand for a special kind of proposition (as it does for us).] The actions of non-human animals show that they too have some thinking principle, though one that is much inferior to the human mind. And everything around us can convince us of the existence of a supreme mind, ·God·, who made the universe and governs it. These are the only minds that reason can give us any certain knowledge about—·our minds, those of the animals below us, and of God above us·.

The mind of man is the noblest work of God that reason reveals to us, and this gives it a dignity that makes it worth studying. But we have to face it: although the human mind is nearer to us than any other objects, and seems the most within our reach, it’s very hard to focus on its workings so as to get a clear notion of them; and that is why able theorists have blundered into greater errors and even absurdities in this branch of knowledge than in any other. These errors and absurdities have led to a general prejudice against all enquiries of this sort. Because able men through the centuries have given different and contradictory accounts of the powers of the mind, it is concluded that all theories about them must be fanciful and illusory.

But however this prejudice may affect superficial thinkers, those with good judgment won’t be apt to be carried away by it.

About two hundred years ago the opinions of men •in natural philosophy were as various and as contradictory as they are now •concerning the powers of the mind. Galileo, Torricelli, Kepler, Bacon, and Newton had the same discouragement in their attempts to throw light on the material system as we have with regard to the intellectual system. If they had been deterred by such prejudices, we would never have reaped the benefit of their discoveries—discoveries that do honour to human nature and will make their names immortal. . . . There’s a natural order in the progress of the sciences, and good reasons can be given why the •philosophy of body should be elder sister to •the philosophy of mind, and should grow up faster; but the •latter has just as much life in it as the •former does, and it will grow to maturity, though slowly. The remains of ancient philosophy on this subject are venerable ruins that have the marks of ability and hard work; they are sufficient to arouse our curiosity but not to satisfy it. In later ages, Descartes was the first to point out the road we ought to take in those dark regions. Malebranche, Arnauld, Locke, Berkeley, Buffier, Hutcheson, Butler, Hume, Price, and Lord Kames have all tried hard to make discoveries, and their efforts haven’t been in vain. Though their conclusions are different and contrary, and though some of them are very sceptical, those conclusions have nevertheless given new light and cleared the way for those who will come after them.

We ought never to despair of human ability. Rather, we should hope that in due course it will produce a system of the powers and operations of the human mind that is just as certain as the systems of optics and astronomy.

We have all the more reason to hope for this because clear knowledge of the powers of the mind would undoubtedly throw much light on many other branches of science. Hume rightly said:

All the sciences have a relation to human nature; and however far any of them may seem to stray from it, they still return back by one route or another. This is the centre—the capital ·city·—of the sciences, and once we are masters of it we can easily extend our conquests everywhere. (Treatise of Human Nature, Introduction)

The faculties of our minds are the tools and engines that we must use in everything we think or say; and the better we understand their nature and force, the more successfully we’ll be able to use them. Locke gives this account of what started him working towards his Essay Concerning Human Understanding:

A few friends meeting in my room and discussing a topic very remote from this soon found themselves brought to a halt by the difficulties that arose on every side. After we had puzzled over them for a while without coming any nearer to solving the problems that perplexed us, it occurred to me that we had gone off-course, and that before embarking of enquiries of that nature we needed to to examine our own abilities, and see which topics our understandings were fitted to deal with and which they were not. . . . (Essay, Letter to the Reader).

If ignorance of the powers of our minds is often the cause of tangled difficulties in discussions that have almost nothing to do with the mind, it must do much more harm in discussions that have an immediate connection with it.

The sciences can be divided into two classes, on the basis of whether they pertain to the material or to the intellectual world. The study of the material world includes:

the various parts of natural philosophy,

the mechanical arts,

chemistry,

medicine,

agriculture.

The study of the intellectual world contains:

grammar,

logic,

rhetoric,

natural theology;

and also,

morals,

jurisprudence,

law,

politics,

the fine arts.

Knowledge of the human mind is the root from which these grow, and draw their nourishment.

So this subject deserves to be cultivated, because of its dignity, its usefulness to the sciences, especially the noblest ones, and. . . .its constituting one way of paying tribute to God.

Essay 1: Preliminary

Chapter 1: Explaining the meanings of some words

Chapter 2: Principles that I take for granted

Chapter 3: Hypotheses

Chapter 4: Analogy

Chapter 5: The right way to get knowledge of the operations of the mind

Chapter 6: The difficulty of attending to the operations of our own minds

Chapter 7: Classifying the powers of the mind

Chapter 8: Social operations of mind

Chapter 1: Explaining the meanings of some words

There is no greater obstacle to the advancement of knowledge than the ambiguity of words. It is the main reason why in most branches of science we find sects and parties, and disputes that are carried on down the centuries without being settled.

Sophistry [= ‘logical trickery’] has been more effectively excluded from mathematics and natural philosophy than from other sciences. In mathematics it had no place from the beginning, because mathematicians had the wisdom to •define their terms precisely and to •lay down as axioms the first principles on which their reasoning was based. And so we find no parties ·or sects· among mathematicians, and hardly any disputes.

Until about a century and a half ago, natural philosophy contained as much sophistry, dispute, and uncertainty as any other science; but at that time it began to be built on the foundation of •clear definitions and •self-evident axioms. Since then natural philosophy has grown quickly, as if watered with the dew of heaven; disputes have stopped, truth has prevailed, and the science has made more progress in two centuries than in two thousand years before.

It would be good if this method that has been so successful in mathematics and natural philosophy—·namely the method that starts with clear definitions and self-evident axioms·—were attempted in other sciences as well; for definitions and axioms are the foundations of all science. I shall now set out some general principles concerning definition. I’m doing this for the benefit of readers who don’t know much about this branch of logic, to spare them from trying to provide definitions in cases where the subject doesn’t allow them.

[The word ‘art’ is coming up in a way that needs attention. In Reid’s time an ‘art’ was any human activity that involves techniques or rules of procedure. ‘Arts’ in this sense include medicine, farming, and painting.] Someone trying to explain any art or science will need to use •many words that are common to all speakers of the language, and •some that are exclusive to that art or science. Words of the latter kind are called terms of the art, and they ought to be clearly explained so that their meaning can be understood.

A definition is just an explanation of the meaning of a word through words whose meanings are already known. Obviously, then, not every word can be defined: a definition must consist of words, and there couldn’t be any definition if there weren’t words already understood without definition. Common words, therefore, should to be used in their common meanings; and if a word has different meanings in ordinary language, these may need to be distinguished, but they don’t need to be defined.

The only words that need to be defined are uncommon ones and ones that are used with an uncommon meaning.

Many words need to be explained but can’t be logically defined. A logical definition—i.e. a strict and proper definition—states

the •kind of things to which the defined word applies, and

the specific •difference marking off the thing’s •species from every other species belonging to that kind.

It is natural to the human mind to class things under various kinds, and then to subdivide every kind into its various species. Often a species can be subdivided into subordinate species, and then it—·i.e. the species·—is considered as a kind. [(1) Reid is here presenting ideas that are usually expressed in terms of genus-difference-species. In the first chapter of Essay 5 he goes through this again, using ‘genus’ throughout and, once, ‘kind or genus’. (2) After saying that ‘no word can be defined unless. . . ’, Reid will infer not that we can’t define ‘London’ but that we can’t define London. All through the coming discussion he wobbles between talk of defining words and defining things. This wobble won’t be cured in the present version.]

This makes it clear that no word can be logically defined unless it stands for a species, because without a species there can’t be a specific difference ·marking off species from kind or genus·, a specific difference is essential to a logical definition. That is why there can’t be a logical definition of an individual thing such as London or Paris.

Individuals are distinguished either by proper names (·‘London’·) or by accidental circumstances of time or place (·‘the city where Thomas Hobbes lived’·); but they don’t have any specific difference, and so they can’t be defined. Equally obviously, the most general words can’t be logically defined, because they aren’t a species of some still more general term.

Indeed, we can’t even define every species of things, because for some species we have no words to express the specific difference. A scarlet colour is of course a species of colour; but how are we to express the specific difference marking off scarlet from green or blue? We can immediately see the difference, but we have no words in which to say what it is.

We are taught these things by logic. But we needn’t appeal to the principles of logic to be convinced that a word can’t be defined if it signifies something that is perfectly simple, not in any way composite. I think it was Descartes who first made this point, which was later fully illustrated by Locke. Though it seems quite obvious, there have been many cases where great philosophers either didn’t know it or didn’t attend to it, and were led by that to create tangles and darkness in the subjects they were dealing with.

When men try to define things that can’t be defined, their definitions will always be either obscure or false. One of the chief defects of Aristotle’s philosophy was his purporting to define the simplest things—such as time and motion—that can’t be, and don’t need to be, defined. [Then Reid gives a contemptuous sketch of the work of ‘the famous German philosopher Wolff’, whose sins, he says, include giving ‘definitions of things that can’t be defined’.]

Discussions of the powers and operations of the mind involves much use of words that can’t be logically defined— no topic involves them more! The simplest operations of our minds must all be expressed by words of this kind. No man can explain by a logical definition what it is to think, to apprehend, to believe, to will, to desire. Everyone who understands the language has some notion of what those words mean, and everyone who is capable of looking in on himself can form a clear and distinct notion of them by attending to the workings of his own mind, but they can’t be logically defined.

So, since we often can’t define words that we have to use in this area, we must as far as possible use common words in their common meanings, sorting out their different senses when they are ambiguous; and when we have to use less common words we must try to explain them as well as we can without the pretence of giving logical definitions when the nature of the thing doesn’t permit it.

·In the remainder of this chapter· I shall offer ·twelve· sets of remarks about the meanings of certain words. Not having definitions of these words, I want to do what I can to prevent ambiguity or obscurity in the use of them. ·Here is a list of the words in question:

1. ‘mind’

2. ‘operation’

3. ‘power’ and ‘faculty’

4. ‘in’ (as in the phrase ‘in the mind’)

5. ‘thinking’

6. ‘perception’

7. ‘consciousness’

8. ‘conceive’, ‘imagine’, ‘apprehend’

9. ‘operations’ versus ‘objects of operations’

10. ‘idea’

11. ‘impression’

12. ‘sensation’ and ‘feeling’

It may be helpful to be able to look them over in advance.·

1. By the mind of a man we understand whatever it is in him that thinks, remembers, reasons, wills. We don’t know what the essence is of body or of mind. We know certain •properties of body, and certain •operations of mind, and it is only in terms of these that we can define or describe them. We define body as that which is extended, solid, movable and divisible, and similarly we define mind as that which thinks. We are conscious that we think, and that we have thoughts of many different kinds, such as seeing, hearing, remembering, wondering what to do, deciding what to do, loving, hating, and many more. We are taught by Nature to attribute all these to one internal principle, and we call this principle of thought the ‘mind’ or ‘soul’ of a man. [See note on ‘principle’ here.]

2. By operations of the mind we understand every mode of thinking of which we are conscious [‘mode of thinking’ = ‘way of thinking’].

It is worth noticing that the various modes of thinking have always, and in all languages as far as I know, been called ‘operations’ of the mind or by names to the same effect. ·In general, the modes of a thing are its states, ways that it is, qualities that it has, details concerning it; but the modes of a mind, in particular, are things that it does·. We attribute to bodies various modes or properties, but not operations properly so called. A body is extended, divisible, movable, inert; it continues in any state that it is put into; every change in its state is the effect of some force acting on it, and the change is exactly proportional to that force, and occurs in precisely the same direction as the force. These are the general •properties of matter, and they aren’t •operations—·i.e. they aren’t things that the matter does·. On the contrary, they all imply that matter is a dead inactive thing—something that moves only as it is moved, and acts only by being acted on.

In contrast with that, the mind is from its very nature a living and active thing. Everything we know about it implies life and active energy; and the reason why all its modes are called its ‘operations’ is that in all or in most of them the mind is not merely passive, like body, but is really and properly active. At all times and in all languages, ancient and modern, the various modes of thinking have been expressed by words that have activity in their meanings, such as ‘seeing’, ‘hearing’, ‘reasoning’, ‘willing’ and the like. So it seems to be the natural judgment of mankind that the mind is active in its various ways of thinking; and that’s why they are called its ‘operations’ and are expressed by active verbs.

You may want to ask: ‘How much weight should we give to this natural judgment? Mightn’t it be merely a vulgar error?’ [In Reid’s day ‘vulgar’ meant ‘of common ordinary not very educated people’. It didn’t imply vulgarity in our sense of that word.] Philosophers who think so certainly have a right to be heard. But until it is proved that the mind is not active in thinking but merely passive, the common way of talking about its operations ought to be followed. We shouldn’t set it aside in favour of some phraseology, invented by philosophers, implying that the mind is merely passive.

3. The words ‘power’ and ‘faculty’, which are often used in speaking of the mind, don’t need much explanation. Every operation presupposes a power in the being that operates; for it is plainly absurd to suppose that something operates without having any power to operate. But there’s nothing absurd about supposing that something has the power to operate but doesn’t operate. Thus I may while sitting have the power to walk, and while remaining silent I may have the power to speak. So: every operation implies power; but the power doesn’t imply the operation.

The ‘faculties’ of the mind and its ‘powers’ are often used as synonymous expressions. But most ·pairs of supposed· synonyms differ in some tiny way that ought to be noticed. As I see it, the word ‘faculty’ is most properly applied to basic and natural powers of the mind, ones that are part of its constitution. Other powers can be acquired through use, exercise or study, and these are called ‘habits’, not ‘faculties’. . . .

4. Writers on the mind frequently distinguish things that are ‘in’ the mind from things that are ‘external’ to it.

The mind’s powers, faculties and operations are things in the mind. Everything of which the mind is the subject is said to be ‘in’ the mind. It is self-evident that some things cannot exist without a subject to which they belong, and of which they are attributes: colour must be in something coloured; shape in something shaped; thought in something that thinks; wisdom and virtue in some being that is wise and virtuous. So when we speak of things ‘in’ the mind, we mean things of which the mind is the subject. Except for the mind itself and things in it, everything else is said to be ‘external’ to the mind. Bear in mind, then, that in describing something as ‘in’ the mind or as ‘external’ to it we are not saying anything about where the thing is, but only about what its subject is ·if it has one·. . . .

5. ‘Thinking’ is a very general word that covers all the operations of our minds, and is so well understood that it doesn’t need any definition.

To ‘perceive’, to ‘remember’, to ‘be conscious’, and to ‘conceive’ or ‘imagine’ are all words used by philosophers and by the vulgar. They stand for different operations of the mind—ones that are distinguished in all languages and by all people who think. I’ll try to use them with their most common and proper meanings, and I think they’re hardly capable of strict definition. But some philosophers of mind have felt free to use them very improperly, corrupting the English language and •running together things that the common understanding of mankind has always led men to •distinguish. So I shall say some things about their meanings, aiming to prevent ambiguity or confusion in the use of them.

6. First, we are never said to ‘perceive’ something of whose existence we aren’t completely convinced. I can •conceive or •imagine a mountain of gold or a winged horse, but no-one says that he •perceives such an imaginary creature. That distinguishes perception from conception and imagination. Secondly, the only things one is said to ‘perceive’ are external objects, not ones that are in the mind itself. When I am pained I don’t say that I perceive pain, but that I feel it or am conscious of it. That distinguishes perception from consciousness. Thirdly, the immediate object of perception must be something present, not something in the past. We can remember past events but we can’t perceive them. I may say ‘I perceive that that man has had small-pox’, but this is a mere figure of speech—though such a familiar one that people don’t notice that that’s what it is. What it means is that I perceive the pits in his face that are certain signs of his having had the smallpox. We say that we perceive •the thing signified (·the past small-pox·), when really we perceive only •the sign (·the present disfigurement·). When the word ‘perception’ is used properly and literally, it is never applied to past things. That distinguishes perceiving from remembering.

In short, ‘perception’ is most properly applied to the evidence that our •senses give us concerning external objects. But as this is a very clear and compelling kind of evidence, the word ‘perception’ is often applied by analogy to the evidence •of reason, or of •testimony when it is clear and compelling. ·But this way of talking is analogical and loose·. The perception of external objects through our senses is a very special and individual operation of the mind, and ought to have a name to itself. And in all languages it has. I don’t know of any English word more suitable for expressing this act of the mind than ‘perception’. ‘Seeing’, ‘hearing’, ‘smelling’, ‘tasting’ and ‘touching’ or ‘feeling’ are words that express the operations associated with each sense; ‘perceiving’ expresses what they all have in common.

There would have been no need for these remarks about ‘perception’ and ‘perceive’ if they hadn’t been misused so badly in philosophical writings about the mind; there’s nothing wrong with how they are used anywhere else! [Reid goes on to name Hume as the worst offender, citing passages in the Treatise implying that perceptions include impressions, ideas, sensations, passions and emotions. Reid scornfully dismisses this.]

7. ‘Consciousness’ is a word used by philosophers to signify the immediate knowledge we have of our present thoughts and purposes, and in general of all the present operations of our minds.

So consciousness is only of things in the present. To speak of ‘consciousness’ of past things, as is sometimes done in everyday talk, is to confuse consciousness with memory; and all such confusions of words ought to be avoided in philosophical discourse. Notice also that one can be ‘conscious’ only of things in one’s mind, not of things external to it. It is all right for me to say that I perceive or see the table at which I am writing, but I shouldn’t say that I am conscious of it. Consciousness is the power by which we know about operations of our own minds; it is quite different from the power by which we perceive external objects; and these different powers have different names in our language and (I believe) in all languages. So a philosopher ought carefully to preserve this distinction, and never to run together things that are so different in their nature.

8. ‘Conceiving’, ‘imagining’ and ‘apprehending’ are commonly used as synonymous in our language, signifying the same thing that logicians call ‘simple apprehension’. This operation of the mind is quite different from any of the ones mentioned above. Whenever we perceive or remember or are conscious of something, we are fully convinced of its existence. But we can conceive or imagine something that doesn’t exist and that we firmly believe doesn’t exist. What never existed can’t be remembered; what doesn’t exist now can’t be the object of perception or of consciousness ·now·; but what never did or does exist can be conceived. . . . Conceiving, imagining, and apprehending, with those words properly understood, are acts of the mind that imply no belief or judgment at all. And an act of the mind by which nothing is affirmed or denied can’t be either true or false.

But those words have another very different meaning which is so common and so well authorised in language that it can’t easily be avoided; and for that reason we ought to be especially on our guard not to be misled by the ambiguity. Politeness and good breeding lead men, on most occasions, to express their opinions with modesty, especially when they differ from others whom they ought to respect. So instead of saying ‘This is my opinion’ or ‘This is my judgment’, which sounds dogmatic, we say, ‘I conceive. . . ’ or ‘I imagine. . . ’ or ‘I apprehend. . . ’, which is understood as a modest declaration of our judgment. Similarly, when someone says something that we take to be impossible, we say ‘I can’t conceive it’, meaning that we can’t believe it.

[Reid goes on to offer a rule of thumb for distinguishing the two senses: in the strict sense we say ‘I conceive [noun phrase]’, e.g. ‘I conceive a pyramid’; in the other sense—the belief-involving one—we say ‘I conceive that [sentence]’, e.g. ‘I conceive that the speed of light is not infinite’. He admits that the rule has exceptions, because one can use the form ‘I conceive [sentence]’ to mean something that is not belief-involving. In a second paragraph he says that in ordinary life we get into no significant troubles because of this ambiguity in those verbs. But the ambiguity, he concludes:] has tangled philosophers discussing the operations of the mind, and it will go on doing so if they don’t attend carefully to the different meanings that those words have on different occasions.

9. Most of the operations of the mind must, from their very nature, have objects to which they are directed. . . . To perceive, you must perceive something; and what you perceive is called the object of your perception. It is impossible to perceive without having any object of perception. The perceiving mind, the object perceived, and the operation of perceiving that object are three distinct things, and are distinguished in the structure of all languages. In the sentence

I ... see (or perceive) ... the moon

we have

the person or mind ... the operation of that mind ... the object.

And this applies equally to most operations of the mind.

In every language such operations are expressed by active transitive verbs. [Reid goes on to say that the grammatical structure that is involved here:

nominative ... active transitive verb ... accusative

enshrines the distinction that he is emphasizing. Which shows] that all mankind—those who invented language and those who use it—have distinguished these three things. . . .

I wouldn’t have needed to explain such an obvious distinction if some systems of philosophy hadn’t muddled it up. Hume’s system, in particular, obliterates any distinction between the mind’s operations and the objects of those operations. When he speaks of ‘ideas of memory’, ‘ideas of imagination’, and ‘ideas of sense’, it is often impossible to gather from the context whether he is using ‘ideas’ to refer to the operations of the mind or to the objects to which they are directed. According to his system, indeed, there isn’t any distinction between the operation and its object.

Of course a philosopher is entitled to look critically even at distinctions that are to be found in the structure of all languages; and if he can

show that some such distinction has no foundation in the nature of the things that are distinguished,

if he can

point out some prejudice shared by all mankind that has led them to distinguish things that are not really different,

in that case such a distinction may be attributed to a vulgar error that ought to be corrected in philosophy. But when from the outset he takes it for granted, without proof, that some distinction found in the structure of all languages has no foundation in Nature, this is surely too dismissive a way of treating the common sense of mankind. When we come to philosophers for instruction, we must bring common sense along with us, judging by its old light the new light that the philosopher is offering us. When we are told to extinguish the old light so that we can follow the new, we have reason to be on our guard! There may be well-grounded distinctions that •have to be made in philosophy but •are not made in ordinary language because they aren’t needed in the everyday business of life. But I don’t think there are any distinctions that •are made in all languages but •don’t have a solid basis in Nature.

10. The word ‘idea’ occurs so frequently in modern philosophical writings about the mind, and is so ambiguous in its meaning, that I have to make some remarks about it. There are chiefly two meanings of this word in modern authors, a •popular and a •philosophical. [Throughout this work ‘popular’ means ‘pertaining to ordinary people’, not ‘widely liked’.]

First, in popular language ‘idea’ means the same as ‘conception’, ‘apprehension’ and ‘notion’.

To have an idea of something is to conceive it.

To have a distinct idea is to conceive it distinctly.

To have no idea of it is not to conceive it at all.

I said earlier that conceiving or apprehending has always been taken by everyone to be an act or operation of the mind, which is why it is expressed in all languages by an active verb. So when we speak of ‘having ideas’, in the popular sense, we should bear in mind that this signifies precisely the same thing that we commonly express by the active verbs ‘conceiving’ or ‘apprehending’. ·Notice that in each of the above three equivalences, there is no noun on the right-hand side corresponding to the noun ‘idea’ on the left·.

When the word ‘idea’ is taken in this popular sense, no-one can possibly question whether he has ideas. In order to •question, one must •think, and to think is to •have ideas.

Sometimes, in popular language, a man’s ideas signify his opinions. The ‘ideas’ of Aristotle signify his opinions. So what I said earlier about the words ‘imagine’, ‘conceive’ and ‘apprehend’ is equally true of ‘idea’—namely that it is sometimes used to mean ‘judgment’. . . . So we see that ‘having ideas’, taken in the popular sense of the phrase, has precisely the same meaning as ‘conceiving’, ‘imagining’ and ‘apprehending’—including their ambiguity! I wonder whether it was at all necessary to introduce ‘idea’ into discourse to signify the operation of conceiving or apprehending. I have shown that we have several other words that mean the same thing—words that began as English or were brought into English long ago and are now naturalized. So why should we adopt a Greek word in place of these, any more than a French or a German word?. . . .

Secondly, according to the philosophical meaning of the word ‘idea’, what it signifies is not the •act of the mind that we call ‘thought’ or ‘conception’ but some •object of thought. According to Locke (whose very frequent use of ‘idea’ is probably what led to its being adopted into ordinary language), ‘Ideas are nothing but the immediate objects of the mind in thinking’ (Essay I.i.8). But of those objects of thought called ‘ideas’ different sects of philosophers have given very different accounts. . . .

[In the next paragraph ‘principle’ means source—see explanation here—but not exclusively ‘ causal source’ in our sense of ‘causal’. The matter from which a thing is made was sometimes called its ‘material cause’, and its form or design or ground-plan was called its ‘formal cause’. Its ‘efficient cause’ was its cause in our sense of that word. There was also a thing’s ‘final cause’, meaning the purpose for which it was made. Consider a coin: its •efficient cause is the stamping of a die on hot metal, its •material cause is the metal it is made of, its •formal cause is its roundness etc., and its •final cause is commerce, the purpose for which it was made.]

The earliest theory of ideas that we have is the one expounded in several of Plato’s dialogues. Many ancient and modern writers have credited Plato with having invented it, but it is certain that he took his doctrine of ideas as well as the word ‘idea’ from the school of Pythagoras. We still have a treatment of ‘the soul of the world’ by a Pythagorean philosopher, in which we find the substance of Plato’s doctrine of ideas. Ideas were held to be eternal, uncreated, and unchanging •forms or •models which God followed in making every species of things that exists, making them out of •matter, which is ·also· eternal. Those philosophers held that there are three first principles of all things:

An eternal matter, out of which all things were made.

Eternal and immaterial forms or ideas, according to which they were made.

An efficient cause, God, who made them.

For the mind of man to be fit to contemplate these eternal ideas, it must (these philosophers held) be purified in a certain way and weaned from things that can be sensed. The eternal ideas are the only object of science [meaning: the only object of knowledge that is certain, fixed, disciplined, deductively organized], because the things we can sense are in a perpetual flux, so that there can be no real knowledge regarding them.

The later Platonists diverged from the earlier ones in their view of the eternal ideas. They held that ideas, rather than being a principle •distinct from God, are conceptions of things •in God’s understanding, the natures and essences of all things being perfectly known to him from eternity.

Note that the Pythagoreans and all the Platonists regarded the eternal ideas as objects of •science and of abstract thought, not of •sense. In this respect the ancient system of eternal ideas differs from the modern one of Malebranche. He was like other modern philosophers in holding that external things are perceived by us not immediately but only through ideas ·acting as intermediaries·. But ·his system was like the ancients ones and unlike the other moderns in this·: he held that the •ideas through which we perceive an external world are the •ideas in God’s mind. The ideas of all things past, present and future must have been in God’s mind from eternity, ·Malebranche held·; and God, who is at all times intimately present to our minds, can reveal to us as much of his ideas as he sees fit, according to certain established laws of Nature. Whatever we perceive of the external world we perceive in his ideas, as though in a mirror.

So there are three systems—·early Platonic, later Platonic, and Malebranchian·—which all maintain that the ideas that are the immediate objects of human knowledge are eternal and unchanging, and existed •before the things they represent. Some other systems hold that the ideas that are the immediate objects of all our thoughts come •after and are derived from the things they represent. We shall give some account of these; but as they have grown out of the ancient Aristotelian system I need to start with some account of that.

[We’re going to encounter the word ‘species’, used as a technical term in Aristotelian philosophy having nothing to do with ‘species’ meaning ‘class that is one step down from a genus’. What Reid says about the Aristotelian ‘species’ will make the technical meaning of the term clear.] Aristotle taught that all the objects of our thought enter at first through our senses; and since our senses can’t take in external material objects they take the •‘species’ of those object, i.e. their •images or their •forms without the matter—compare wax taking the form of the seal without any of its matter. These images or forms that are impressed on the senses are called ‘sensible species’, and it is only the •sensing part of the mind that engages with them. But various powers of the mind go to work to retain, refine, and spiritualize them so that they can become objects of •memory and •imagination and—eventually—of •pure thought. As objects of memory and of imagination they are called ‘phantasms’; and when through further refinement and removal of all their particular details they become objects of science, they are called ‘intelligible species’. So that every immediate object, whether of sense, memory, imagination or reasoning must be a phantasm or species in the mind itself. . . .

Why do I give this sketch of •what the Aristotelians maintained regarding the immediate objects of our thoughts? Because the doctrine of modern philosophers concerning ideas is built on •it. Locke, who uses the word ‘idea’ so very often, tells us that what he means by it is the same as is commonly meant by ‘species’ or ‘phantasm’ (Essay I.i.8). Gassendi, from whom Locke borrowed more than from any other author, says the same. The words ‘species’ and ‘phantasm’ are terms of art [= ‘technical terms’] in the Aristotelian system, and their meaning has to be learned from that.

Democritus and Epicurus had a position on this subject that was quite like that of the Aristotelians. They held that all bodies continually send out slender films or spectres from their surface—ones that are so extremely fine that they easily penetrate our thick bodies, entering by the organs of sense and stamping their image on the mind. [In Reid’s day the core meaning of ‘image of x’ was ‘likeness of x’.] The ‘sensible species’ of Aristotle were mere forms without matter. The ‘spectres’ of Epicurus were composed of a very rarefied matter.

Modern philosophers, as well as the Aristotelians and Epicureans of old, have believed that external objects can’t be the immediate objects of our thought; that there must be some image of them in the mind itself, and that the external thing is seen in ·or by means of· its mental image, like seeing something in ·or by means of· a mirror. And the name ‘idea’, in its philosophical sense, is given to those •internal and immediate objects of our thoughts. The external thing is the •remote or mediate object; but the idea or image of that object in the mind is the immediate object, without which we could have no perception, no memory, no conception of the mediate object. ·To make quite sure that that is clearly grasped: When I see a tree, my idea or mental image of the tree is the immediate object of my perception—immediate because nothing comes between it and my perceiving mind. The tree is the mediate or mediated object of my perception, because something does come between it and my mind, namely its idea or image·.

So here is how things stand. When in ordinary language we speak of having an ‘idea’ of something, all we mean is thinking of it. The vulgar allow that this expression implies

•a mind that thinks,

•an act of that mind that we call ‘thinking’, and

•an object about which we think.

But, besides these three, the philosopher believes that there is a fourth, namely

•the idea that is the immediate object ·of the thinking·.

The idea is in the mind itself, and can’t exist except in a mind that thinks; but the remote or mediate object may be something external, like the sun or the moon; it may be something past or future; it may be something that never existed. This is the philosophical meaning of the word ‘idea’; and I would point out this meaning of that word is built on a philosophical opinion. For if philosophers hadn’t believed that there are such immediate objects of all our thoughts in the mind, they wouldn’t have used the word ‘idea’ to stand for them!

One last remark about this: although I may have occasion to use the word ‘idea’ in this philosophical sense in explaining the opinions of others, I shall have no occasion to use it in expressing my own, because I believe ‘ideas’ in this sense to be a mere fiction of philosophers. And there isn’t much use for it in its popular meaning either, because the English words ‘thought’, ‘notion’ and ‘apprehension’ serve as well as the Greek word ‘idea’, and they have the advantage of being less ambiguous ·than ‘idea’ is·. . . .

11. Hume, in speaking of the operations of the mind, uses the word ‘impression’ almost as often as Locke uses ‘idea’. What Locke calls ‘ideas’ Hume divides into two classes; he calls the members of one class ‘impressions’, those of the other ‘ideas’. I shall make some remarks about Hume’s explanation of the word ‘impression’, and then consider its proper meaning in the English language.

Hume writes:

We can divide all the perceptions of the human mind into two classes or species, distinguished by their different degrees of force and liveliness. The less lively and forcible are commonly called ‘thoughts’ or ‘ideas’. The other species lack a name in our language and in most others; so let us use a little freedom and call them ‘impressions’. By the term ‘impressions’, then, I mean all our more lively perceptions when we hear or see or feel or love or hate or desire or will. Ideas are the less lively perceptions that we are conscious of when we reflect on any of those sensations or feelings mentioned above. (Hume, Enquiry Concerning Human Understanding, section 2.)

He explains the term ‘impression’ in the same way in his Essays and in his Treatise of Human Nature.

. . . . Hume’s terminology in the passage I have quoted is faulty ·in three ways·. (1) He gives the name ‘perception’ to every operation of the mind. Love is a perception, hatred a perception. Desire is a perception, will is a perception; and by the same rule any doubt or question or command is a perception. This is an intolerable misuse of language, and no philosopher is entitled to introduce it.

(2) When Hume says ‘We can divide all the perceptions of the human mind into two classes or species, distinguished by their different degrees of force and vivacity’, his manner of writing is loose and unphilosophical. To differ in •species is one thing, to differ in •degree is another. Things that differ only in degree must be of the same species. It is a maxim of common sense which everyone accepts that greater and less don’t make a difference of species. If a man has different ‘degrees of force and liveliness’ at different times (e.g. when he is healthy and when he is sick), that doesn’t put him into different •species at those times! It doesn’t stop him from being the very same •individual man at each time. . . . Differences of degree are distinct from differences of ·kind or· species, and every thinking person knows how to tell them apart.

(3) Having given the general name ‘perception’ to all the operations of the mind, and separated them into two classes or species according to their degree of force and liveliness, Hume tells us that he gives the name ‘impression’ to all our more lively perceptions, namely ‘when we hear or see or feel or love or hate or desire or will’. There is great confusion in this account of the meaning of the word ‘impression’.

When I see, this is an impression. But why hasn’t Hume told us whether he gives the name ‘impression’ to the •object I see or to the •act of my mind by which I see it? When I see the full moon, the moon is one thing and my perceiving it is another. Which of them does Hume call an ‘impression’? We are left to guess; and the rest of what Hume writes about impressions doesn’t throw light on this point.

Everything he says tends to darken it, leading us to think that •the moon that I see and •my seeing it are not two things but one and the same thing. . . . When I read all that he has written on this subject I find that he uses word ‘impression’ sometimes to signify an operation of the mind, and sometimes to signify the object of the operation; but usually it is a vague and unsettled word that signifies both.

. . . .Hume’s theory of mind required a language differently structured from ordinary language; if his views had been expressed in plain English they would have been too jarring to the common sense of mankind. For example: If you are given something that you highly value, if you see it and handle it and put it in your pocket, this, says Hume, is an •impression. If you only dream that you received such a gift, this is an •idea. And what is the difference between this impression and this idea—between the reality and the dream? They belong to different classes or species, says Hume, and in that we will all agree with him. But he adds that they differ only in their degrees of force and liveliness! Here he slips in a doctrine of his own that contradicts the common sense of mankind. Common sense convinces everyone that a lively dream is no nearer to a reality than a faint one, and that a man could dream that he had all the wealth of Crœsus without getting a farthing more in his pocket. It is impossible to construct arguments against such undeniable principles except by confusing the meaning of words. . . . The power of words is so great that if someone can get us into the habit of giving a single name to •two things that are connected, it will be that much easier to get us to believe that they are •one thing.

Now let us consider the proper meaning of ‘impression’ in English, to see how suitable it is to signify either the operations of the mind or their objects.

When a figure is stamped on a body by pressure, that figure is called an ‘impression’—e.g. the impression of a seal on wax, of printing-types on paper. This seems now to be the literal sense of the word, the effect borrowing its name (·‘impression’·) from what caused it (·the pressure on the wax or paper·). But its meaning gets stretched, by metaphor or analogy, so that it comes to signify any change produced in a body by the operation of some external cause. Slapping a stone wall makes no impression on it, but shooting a cannon at it can do so. The moon raises a tide in the ocean but makes no impression on rivers and lakes. (Most words have their meanings extended by metaphor or analogy, in some such way as this.)

We also speak of ‘making an impression’ on the mind. ‘Advice and criticism make little impression on someone who is confirmed in bad habits.’ ‘That speech when delivered in one way makes a strong impression on the hearers; delivered in another way it makes no impression at all.’ Such uses of ‘impression’ take the word still further from its literal meaning; but this is authorized by use, which is the arbiter of language.

Notice that in such examples, ‘making an impression’ on a mind always implies some change of •purpose or will, some new •habit produced or some former habit weakened, some •emotion aroused or quietened. When such changes are produced by persuasion, example or any ·other· external cause, we say that such causes ‘make an impression’ on the mind. But when things are seen or heard or taken in without producing any passion or emotion, we say that they ‘make no impression’.

In the broadest sense of the word, an ‘impression’ is a change produced in some •passive thing through the operation of an external cause. When an •active thing produces some change in itself through its own active power, this is never called an ‘impression’. It is an act or operation of the thing, not an impression on it. So we see that to give the name ‘impression’ to an effect produced in the mind is to imply that the mind doesn’t act in the production of that effect. If seeing, hearing, desiring, willing are operations of the mind, they can’t be impressions. If they are impressions, they can’t be operations of the mind. In the structure of all languages they are considered as acts or operations of the mind itself, and the names given to them—·specifically the active verbs·—imply this. To call them ‘impressions’, therefore, is to trespass against the structure not of this or that particular language but of all languages.

If the word ‘impression’ can’t be properly used to signify the •operations of the mind, it is at least as improper to signify their •objects. If someone said that the sun is an impression, that the earth and the sea are impressions, wouldn’t we conclude that he was just misusing language?

·Before leaving this topic, I want to offer a thought about how •misuse of language relates to •wildly false beliefs·. It is commonly believed and taken for granted that as long as a language—any language—has enough words, it is perfectly fit to express any opinion, whether true or false. But this isn’t absolutely true, for a reason that deserves to be attended to.

The structure and •grammar of all ·actual· languages are based on certain common •opinions of mankind. For as long as these opinions are common to all men, there will be a great similarity in all languages on our planet. And there is such a similarity; for we find in all languages the same parts of speech,

the distinction between adjectives and nouns,

the distinction between both of those and verbs,

the distinction between active and passive verbs,

the uses of verbs with different tenses, moods, persons and numbers

And there are general rules of grammar, the same in all languages. This similarity of structure in all languages shows that people all hold the opinions on which the structure of language is based.

•Suppose that some nation believed that the things we call ‘attributes’ might exist without a subject, ·i.e. without there being anything for them to be attributes of ·. Their language wouldn’t have a distinction between adjectives and nouns, nor would they have the rule that an adjective has no meaning unless it is joined to a noun. •Or suppose a nation who didn’t distinguish acting from being acted on: their language would have no distinction between active and passive verbs. . . .

The structure of all languages is based on common notions, which Hume’s philosophy opposes and tries to overturn. No doubt this is what led him to bend the common language into conformity with his principles; but we oughtn’t to go along with him in this until we are satisfied that his principles are built on a solid foundation.

12. ‘Sensation’ is a name that philosophers give to an act of the mind that can be distinguished from all others by this, that it has no object distinct from the act itself. Pain of every kind is an unpleasant sensation. When I am in pain I can’t say that •the pain I feel is one thing and •my feeling it another. They are one and the same thing, and I can’t even imagine having the pain but not feeling it, or feeling it without having the pain. When pain isn’t felt, it doesn’t exist. It is of whatever kind it is felt to be, and can’t be more or less intense, longer- or shorter-lasting, than it is felt to be. It can’t exist by itself—·it has to be had by something·—and it can’t be had by anything except a sentient being. No quality of an inanimate non-sentient being can be anything remotely like it.

All this applies equally to every other ·kind of· sensation. Some of them are more or less •pleasant, others more or less •unpleasant, and we pay some attention to these because we want to •have or to •avoid them. But many kinds of sensations are neutral—not nice and not nasty—and we pay little attention to them; these have no name in any language.

Most mental operations that have names in ordinary language are inherently •complex, made up of various ingredients, various •simpler acts. These are combined in our constitution; but if we are to have a clear and scientific notion of the complex operation, we must be able to separate the simpler acts from one another by abstraction. People who don’t attend to the complex nature of such operations are apt to equate them with some •one of the simple acts of which they are made up, overlooking •the others; and this has caused many disputes and errors concerning the nature of such operations.

Now, such complex operations usually have sensation as one ingredient. The perception of an external object is accompanied by a sensation corresponding to the object, and in many languages such sensations are given the same name as the external object that they always accompany. (·For example, ‘I have a sensation of green’, meaning ‘I have a sensation as of seeing something green’·.) When two or more things (a) are constantly conjoined in the course of Nature, and (b) have the same name as one another in all languages, it is hard to separate them by abstraction; and that difficulty has led to many errors in the philosophy of the mind. For the avoidance of such errors nothing matters more than to have a clear notion of the simple act of the mind that we call ‘sensation’, and I have tried to describe that. This will make it easier to distinguish sensation from every external object that it accompanies, and from every other act of the mind that may occur along with it. It is also important that in philosophical writings the word ‘sensation’ should be used exclusively to name this simple act of the mind. . . .

I shall add some remarks about the word ‘feeling’. This word has two meanings. (a) It signifies the perceptions we have of external objects through the sense of touch. When we speak of ‘feeling’ a body to be hard or soft, rough or smooth, hot or cold, we are saying that we perceive these things by touch. They are external things, and the act of the mind by which we feel them is easily distinguished from the objects that are felt. (b) The word feeling is ·also· used to signify the same thing as ‘sensation’ signifies, which I have just finished explaining; and in this sense a feeling has no object—•the feeling and •what is felt are one and the same.

Perhaps there is a small difference in meaning between ‘feeling’ in sense (b) and ‘sensation’. We usually use ‘sensation’ to name the feelings that we have through our external senses and bodily appetites, and all our bodily pains and pleasures. But there are feelings of a nobler nature accompanying our affections, our moral judgments, and judgments in matters of taste, and it would be less appropriate to call these ‘sensations’. . . .

Chapter 2: Principles that I take for granted

Just as there are •words common to philosophers and to the vulgar, which don’t need to be •explained, so also there are •principles common to both, which don’t need to be •proved and cannot be directly proved.

Someone who applies himself to any branch of science must have reached an age at which he is intellectually mature, so he must have used his reason and his other mental powers in various ways. He must have formed various opinions and principles by which he conducts himself in the affairs of life. Some of those principles are common to all men, being evident in themselves and so necessary in the conduct of life that a man can’t live and act according to the rules of common prudence without them.

Everyone who has ordinary intelligence accepts such principles, and regards anyone who denies or questions them as either mad or lacking in common sense. Suppose someone didn’t believe his own eyes and put no trust in his senses, would anyone think it worthwhile to reason gravely with him, trying by argument to convince him of his error? Surely no wise man would. For men can’t reason together unless they agree on first principles: it is impossible to reason with someone who has no principles in common with you.

So there are common principles, which are the basis of all reasoning and of all science. They seldom admit of direct proof, and they don’t need it. Men don’t need to be taught these common principles, because they’re things that all normally intelligent men •know—or at least •readily agree to as soon as they are proposed and understood.

When we have occasion to use such principles in science, we call them ‘axioms’. It isn’t absolutely •necessary to point out the principles or axioms on which a science is based, but it can be very •useful to do so.

Mathematicians, for example: before proving any of the propositions of mathematics they lay down certain axioms, or common principles, on which they build their reasonings. These axioms are truths that everyone knew already—e.g. ‘The whole is greater than a part’, ‘Equal quantities added to equal quantities make equal sums’—·but it is worthwhile to set them out explicitly·. When we see that the proof of a mathematical proposition assumes nothing but such self-evident axioms, the proposition seems more certain, leaving no room for doubt or dispute.

Every other science will also be found to have a few common principles on which all the reasonings in that science are based. . . . If these were pointed out and considered, we could make a better job of evaluating the conclusions in that science. If the principles are certain, the conclusions soundly inferred from them must be certain. If the principles are only probable, so are the conclusions. If the principles are false, dubious, or obscure, that weakness must infect the superstructure that is built on them.

Sir Isaac Newton, the greatest of natural philosophers, has given an example that is well worth copying, by laying down the common principles or axioms on which reasonings in natural philosophy are built. Before this was done, the reasonings of philosophers •in that science were as vague and uncertain as they are •in most others. Nothing was fixed; all was dispute and controversy; but Newton’s very satisfactory procedure laid a solid foundation for that science, and a grand superstructure ·of physical theory· has been raised on it—one about which there is now no more dispute or controversy among knowledgeable people than there is about the conclusions of mathematics.

Still, the first principles of natural philosophy are quite different in kind from mathematical axioms, in the following way. They aren’t evident in the way that •mathematical axioms are, and they aren’t necessary truths like •them. They are the likes of these:

•Similar effects come from the same or similar causes.

•The only causes we should accept for natural effects are ones that are true, and that do account for the effects.

These principles don’t have the same kind of evidentness as mathematical axioms, but they are nevertheless very evident—enough so that every person with normal intelligence readily accepts them and finds it absolutely necessary to steer by them in his everyday actions and opinions.

I think it may be useful—though this isn’t usually done— to declare some of the things that I shall take for granted as first principles in my discussion of the mind and its faculties. There is special reason for doing this in the fact that very able men such as Descartes, Malebranche, Arnauld, Locke and many others have given themselves needless trouble by not distinguishing •things that need proof from •things that can perhaps be illustrated but can’t be proved because they are self-evident. When men try to deduce such self-evident principles from others that are even more evident they always fall into inconclusive reasoning; and this has had the result that others, such as Berkeley and Hume, ·rightly· thinking that the arguments brought to prove such first principles are weak and inconclusive, have been tempted first to doubt those principles and then to deny them.

It is so tiresome to reason with someone who denies first principles that wise men usually refuse to do so. •But ·there may be reason to argue about something that someone thinks to be a first principle, because· it can happen that what is only a vulgar prejudice is mistaken for a first principle. •And ·there may be reason to offer support, of a kind, for a genuine first principle, because· a genuine first principle may, by the enchantment of words, have so much mist thrown around it that its evidentness is hidden, which could make an honest person doubt its truth. Cases of this latter kind may occur more often in this science [here = ‘the philosophy of mind’] than in any other; but ·they don’t bring it a halt, because· there is some remedy for them. When first principles are called into question, there are ways of making their evidentness more apparent; but these ‘ways’ are very special to this particular problem. The evidentness of the procedures is not demonstrative, but intuitive; the first principles don’t need to be proved, but merely shown in the right light.

I’ll show this more fully in the proper place, in application to the very principles that I now assume. In the meantime, when I propose something as a ‘first principle’—·as I shall do in the following list of eight of them·—you should be on your guard, and should consider whether it really is entitled to that label.

1. I shall take it for granted that I think, that I remember, that I reason, and in general that I really perform all the mental acts of which I am conscious.

The operations of our minds are accompanied by consciousness, which is our evidence—the only evidence we can have—of their existence. If someone takes it into his head to think or to say that his consciousness might deceive him, and to demand proof that it can’t do so, I don’t know of any proof we can give him. We have to leave him to himself, as someone who denies first principles that are needed for all reasoning. Everyone finds that he has to believe what consciousness tells him, and everything that has this testimony should be taken as a first principle.

2. Just as by •consciousness we know for sure the existence of our •present thoughts and emotions, so by •remembering we know the •past. And when events are recent and the memory of them fresh, the knowledge of them that such clear remembering gives us is second only—in certainty and evidentness—to that of consciousness.

3. We are conscious of many things to which we give littleor no attention. We can hardly attend to several things at once, and our attention is usually directed to •whatever it is that we are thinking about, and only rarely to •the thought itself. For example, what an angry man attends to is the wrong that has been done to him or the person who has done it; as for his anger—he is conscious of that but he doesn’t attend to it. But when we reach years of maturity we have it in our power to pay attention to our own thoughts and feelings and the various operations of our minds. When we focus on these—when they are present or recent and fresh in our memory—this act of the mind is called ‘reflection’.

So I take it for granted that by attentive reflection a man can have knowledge of the operations of his own mind—a knowledge that is as clear and certain as his knowledge of an external object when it is set before his eyes. . . . A man must be convinced beyond possibility of doubt of everything concerning the operations of his own mind that he clearly and distinctly discerns by attentive reflection.

4. I take it for granted that all the thoughts I am conscious of or remember are the thoughts of a single thinking principle, which I call ‘myself’ or ‘my mind’. [See note about ‘principle’ here.] Everyone has an immediate and irresistible belief not only in his present existence but in his continuous existence and identity as far back as he can remember. If anyone thinks fit to demand a proof •that the thoughts he is successively conscious of belong to one thinking principle—•that he is the same person today as he was yesterday or a year ago—I don’t know of any proof that can be given to him. He must be left to himself, either as a lunatic or as someone who denies first principles and ·therefore· can’t be reasoned with. . . .

5. I take it for granted that there are some things that can’t exist by themselves and must be in something else to which they belong as qualities or attributes.

For example, motion can’t exist except in something that is moved. To suppose that there could be motion while no thing was moving is a gross and obvious absurdity. Similarly, hardness and softness, sweetness and bitterness, are things that can’t exist by themselves; they are qualities of something that is hard or soft, sweet or bitter. The thing, whatever it may be, of which they are qualities is called their ‘subject’. . . .

Things that can exist by themselves and don’t necessarily presuppose the existence of anything else are called substances; they are the subjects of the qualities or attributes that belong to them.

Anything that we •immediately perceive by our senses or •are conscious of is something that must be in something else as its subject. Thus by my senses I perceive shape, colour, hardness, softness, motion, resistance, and such things; these are qualities, and must necessarily be in something that is shaped, coloured, hard or soft, moving, resisting. The name ‘body’ is applied not to these qualities but to their subject, ·i.e. the thing that has them·. If anyone should think fit to deny that these things are qualities, or that they require a subject, I leave him to enjoy his opinion as a man who denies first principles and isn’t fit to be reasoned with. If he has ordinary intelligence he will find that he can’t have a half-hour conversation without saying things that contradict what he says he believes.

Similarly, the things that I’m conscious of—such as thought, reasoning, desire—necessarily presuppose something that thinks, that reasons, that desires. We don’t give the name ‘mind’ to thought, reason or desire, but to the thing that thinks, reasons, and desires. So these propositions:

Every act or operation presupposes an agent,

Every quality presupposes a subject,

are things that I don’t try to prove, but take for granted. Every ordinarily intelligent man sees these immediately and can’t have the least doubt about them.

[Then Reid contends that ‘the grammar of all languages’ supports these principles, mostly repeating things he said a few pages back.]

6. I take it for granted that most operations of the mind must have an object distinct from the operation itself. I can’t see without seeing something. To see without having any object of sight is absurd. I can’t remember without remembering something. The remembered thing is past, so it must be distinct from my remembering of it, because that is present. The operations of our minds are expressed in all languages by active transitive verbs, and the sheerly grammatical properties of these require not only a person or agent but also an object of the operation.

Thus the verb ‘know’ signifies an operation of mind. From the general structure of language, this verb requires a person: I know, you know, he or she knows. But it equally requires a noun in the accusative case signifying the thing that is known; for someone who knows must know something. . . .

7. We ought likewise to take for granted as first principles things on which there is universal agreement, among the learned and the uneducated, in the different nations and ages of the world. Such widespread consent. . . .ought at least to have great authority unless we can show how it might have been caused by some equally universal prejudice. Truth is •one, but error is •infinite. Many truths are so obvious to the human faculties that it can be expected that men should universally agree in them.

And that’s what we find with regard to many truths, ones that no-one dissents from except perhaps a few sceptical philosophers, and we can fairly suspect them of differing from the rest of mankind through pride, obstinacy, or some obsession. When there is such universal agreement on things that aren’t deep or intricate, but which lie as it were on the surface, there is the strongest possible presumption that it is a natural result of the human faculties; and it must have great authority with every serious mind that loves truth. . . . You may think: ‘It is impossible to collect the opinions of all men about anything, so that this maxim can’t be of any use.’ But in many cases it is possible. Consider these:

•There is a material world, and the things we see and handle are real, and not mere illusions and apparitions.

•Everything that begins to exist, and every change that happens in Nature, must have a cause.

•There is a right and a wrong in human conduct— things that in certain circumstances we ought to do, and other things that we ought not to do.

Who can doubt whether mankind have in all ages believed these? The universality of these opinions and of many others that might be named is sufficiently evident from the whole course of men’s conduct, as far as our acquaintance reaches, and from the records of history that are transmitted to us.

[Reid now repeats that some ‘opinions’ are embedded in ‘the structure of all languages’, which is evidence that everyone has always accepted them. Then:] I shall often have occasion to argue from the sense of mankind as expressed in the structure of language, so it was appropriate to call attention here to arguments drawn from this topic.

8. I need hardly say that I shall also take for granted facts that all sober and reasonable men accept on the testimony of their senses, of their memory, or of other people. Although some writers on this subject have questioned the authority of the senses, of memory, and of every human faculty, we find that these people in the conduct of life—in pursuing their ends, or in avoiding dangers—give the same authority to their senses and other faculties as do the rest of us. This entitles us to doubt the sincerity of their professions of scepticism.

This, indeed has always been the fate of the few who have professed scepticism: having done their best to discredit their senses, they find themselves having to trust them after all. Hume has openly admitted this; and it is no less true of those who haven’t been as open about it. I never heard that any sceptic ran his head against a post or stepped into a canal because he didn’t believe his eyes.

I agree that in general we ought to be careful not to accept as first principles opinions that aren’t entitled to that status. But the risk of that is minimized when the principles are openly declared, and thus exposed to the examination of any who may dispute their authority. I don’t claim that things laid down as first principles shouldn’t be examined, and that we oughtn’t to listen to what may be argued against their being accepted as principles. Let us deal with them as an upright judge does with a witness who has a good character. He accepts the testimony of such a witness while his character is not challenged; but if it can be shown that he has been bribed or is influenced by malice or personal bias, the judge won’t believe his testimony and will rightly reject it.

Chapter 3: Hypotheses

Every branch of human knowledge has its own principles, its own foundation and method of reasoning; and if we try to build it on any other foundation it will never stand firm and stable. Thus the historian builds on •testimony, and rarely engages in •conjecture. The antiquarian mixes •conjecture with •testimony, and conjecture is often the larger ingredient. The mathematician pays no attention to either testimony or conjecture, and deduces everything by demonstrative reasoning from his definitions and axioms. In fact, anything that is built on conjecture shouldn’t be called a ‘science’, because conjecture can generate opinion but it can’t produce knowledge, ·and science properly so-called should consist entirely of knowledge·. Natural philosophy must be built on the phenomena of the material system, discovered by observation and experiment.

When men first began to philosophise—i.e. to take their thoughts beyond the objects of sense and to enquire into the •causes of things and the secret •operations of Nature—it was very natural for them to engage in conjecture; and it wasn’t to be expected that they would soon discover the right scientific way of proceeding in philosophical investigations. And so it is that the most ancient systems in every branch of philosophy turn out to be nothing but the conjectures of men who were famous for their wisdom and whose fame gave authority to their opinions. Thus, in ancient times wise men conjectured that this earth is a vast plain surrounded by a boundless ocean, and that the sun, moon, and stars emerge from this ocean at their rising and plunge back into it at their setting.

With regard to the mind, primitive men are apt to conjecture that the source of life in a man is his breath; because the most obvious difference between a living man and a dead one is that one breathes and the other doesn’t. That is why in ancient languages the word that stands for the soul is one that strictly means ‘breath’ or ‘air’.

As men come to know more, their first conjectures seem silly and childish and are replaced by others that square better with later observations and discoveries. Thus one system of philosophy takes over from another, without any claim to being better in any way except that it is a more ingenious system of conjectures that accounts better for common appearances.

Skipping over many ancient systems of this kind, we come to Descartes, about the middle of the last century. He was dissatisfied with the ‘prime matter’, the ‘substantial forms’ and the ‘occult qualities’ of the Aristotelians, and boldly conjectured that

the planets in the solar system are carried round by a whirlpool of subtle [= ‘very finely divided, fluid’] matter, just as straws and chaff are carried round in a tub of water.

He had a conjecture about the soul, namely:

The soul is seated in a small gland in the brain, called the pineal gland. It sits there, as though in a reception room, and receives information about everything that affects the senses, brought by a subtle fluid—called the ‘animal spirits’—contained in the nerves. And the soul sends these animal spirits as its messengers to get the various muscles of the body moving, when there is a call for it.

By conjectures like these Descartes could account for every phenomenon in Nature, doing this so plausibly that for more than half a century a great part of the learned world was satisfied with his account.

Such conjectures in philosophical [here = ‘scientific’] matters are generally known as ‘hypotheses’ or ‘theories’. And it has been considered the highest attainment of a philosopher to invent a hypothesis, based on slight probabilities, which accounts for many natural phenomena. If the hypothesis hangs together well, is decorated by a lively imagination, and serves to account for familiar appearances, many people think that it has •all it needs to deserve that we should believe it, and •all that ought to be required in a philosophical system.

Highly talented men are given to inventing hypotheses, and others are given to accepting them as the utmost that the human faculties can reach in philosophy. These two facts make it enormously important for the progress of real knowledge that we should have a clear and distinct understanding of •the nature of hypotheses in philosophy, and of •the respect that should ·as well as the respect that shouldn’t· be paid to them.

Some conjectures may have a considerable degree of probability, but obviously it is in the nature of a conjecture to be uncertain. In every case the assent should be proportioned to ·the strength of· the evidence, because it is a clear misuse of our understanding to believe firmly something that has only a low probability. Well, now, we can quite often form very probable conjectures concerning the •works of men, but any conjecture we can form concerning the •works of God has as little probability as the conjectures of a child concerning the works of a grown man.

God’s wisdom exceeds that of the wisest man more than that man’s wisdom exceeds that of a child. Suppose a child conjectures •how an army should be drawn up on the day of battle, •how a city should be fortified, •how a state should be governed—what are his chances of guessing right? That is how little chance a man—even the wisest man—has of being right when he claims to conjecture how •the planets move in their courses, •how the tides rise and fall, and •how our minds act on our bodies.

Suppose that a thousand of the best minds that the world ever produced, having no previous knowledge of anatomy, were to sit down and try to work out •how and •by what internal organs the various functions of the human body are carried on—how blood is made to circulate and the limbs to move. In a thousand years they wouldn’t arrive at anything like the truth!

Of all the discoveries that have been made concerning the inner structure of the human body, not one was arrived at through conjecture. Precise observations of anatomists have brought to light countless devices of Nature in the make-up of this machine of the human body—devices that we can’t help admiring as excellently adapted to their various purposes. But. . . .no-one ever dreamed of them before they were discovered. In contrast with this, countless conjectures formed down the centuries concerning the structure of the body have been refuted by observation, and none has ever been confirmed.

What I have just said about the internal structure of the human body holds equally for every other part of the works of God about which any real discovery has been made. Such discoveries •have always been made by patient observation, by precise experiments, or by conclusions drawn through strict reasoning from observations and experiments; and they •have always tended to refute and not to confirm the theories and hypotheses that ingenious men had invented.

This fact has been confirmed by the history of philosophy in all past ages, so it ought to have taught men long ago to regard hypotheses in every branch of philosophy with justified contempt, and to give up any hope of advancing real knowledge in that way. The Indian philosopher who didn’t know how the earth was supported invented the hypothesis of a huge elephant, which he then supposed to stand on the back of a huge tortoise. [This refers to Locke’s Essay II.xxiii.2.] Ridiculous as this hypothesis seems to us, it might seem very reasonable to other Indians who didn’t know any more than that one did. And that will be the fate of all hypotheses invented by men to account for the works of God: they may have a decent and plausible appearance to those who don’t know any more than their inventors do, but when men come to be more enlightened those hypotheses will always appear ridiculous and childish. . . .

The finest productions of human art fall far short of the lowest works of Nature. The most careful artist can’t make a feather or a tree-leaf. •Human workmanship will never be in any way comparable with •divine. Well, conjectures and hypotheses are man’s work, and must reflect the capacity and skill of their inventors; so they will always be very unlike the works of God which it is the business of philosophy to discover.

For centuries the world has been duped by hypotheses in every branch of philosophy; so it’s of the utmost importance, for anyone who wants to make any progress in real knowledge, to brush hypotheses aside as the dreams of vain and fanciful men whose pride makes them think they can unfold the mysteries of Nature by the force of their thought. A learned man in a letter to Descartes wrote something that very much deserved the attention of that philosopher and of all who come after him:

When someone tries to investigate Nature while sitting in his study and consulting only his books, he may indeed tell how he would have made the world if God had given him the job; that is, he may describe chimeras that correspond to the weakness of his mind just as well as the admirable beauty of the universe corresponds with the infinite perfection of God; but, lacking a truly divine intellect, he can never form in his own mind an idea like the one God had in creating things. (Descartes, Passions, Preface)

Let us, therefore, adopt this as a basic principle in our enquiries into the structure and workings of the mind: No attention should be paid to the conjectures or hypotheses of philosophers, however ancient and however widely accepted. Let us accustom ourselves to test every opinion by the touchstone of fact and experience. Anything that can fairly be deduced from facts that have been duly observed or sufficiently testified to is genuine and pure; it is the voice of God, and not a fiction of human imagination.

The first rule of philosophising laid down by the great Newton is this:

The only causes of natural effects that should be admitted are ones that are both true and sufficient for explaining the phenomena.

This is a golden rule; it is the true and proper test for distinguishing what is sound and solid in philosophy from what is hollow and vain.

So when a philosopher claims to show us the cause of some natural effect, whether relating to matter or to mind, we should first ask whether there is sufficient evidence that the cause he assigns really does exist. If there isn’t, send it packing as a fiction that oughtn’t to have any place in genuine philosophy. If the cause assigned really does exist, ask next whether the effect it is supposed to explain really does follow necessarily from it. Unless it satisfies these two conditions, it is good for nothing.

When Newton had shown the wonderful effects of gravitation in our planetary system, he must have felt a strong desire to know its cause. He could have invented a hypothesis for this purpose, as many had done before him. But his philosophy wasn’t like that. Listen to what he says:

I have not yet been able to deduce from phenomena the reason for the properties of gravity, and I don’t make up hypotheses. For whatever is not deduced from the phenomena must be called a ‘hypothesis’; and hypotheses, whether metaphysical or physical— whether based on occult qualities or on mechanical ones—have no place in experimental philosophy.

[In this, ‘make up’ replaces Reid’s ‘feign’. In the Latin (which he also gives) the relevant word is fingo, which is the source of ‘feign’ and also of ‘fiction’. Newton was saying in effect ‘I don’t fake hypotheses’.]

Chapter 4: Analogy

It is natural for men to form opinions about less well-known things on the basis of some similarity they see (or think they see) between those things and others that are more familiar or better known. In many cases we have no better way than this of reaching any opinions. And when the things that are compared really are very similar in their nature, and there’s reason to think that they are subject to the same laws, such conclusions drawn from analogy can have a quite high probability .

For example, we can see a very great similarity between our earth and the other planets—Saturn, Jupiter, Mars, Venus, and Mercury. •They all revolve around the sun as the earth does, although at different distances and in different periods. •They borrow all their light from the sun as the earth does. •Some of them are known to revolve round their axis like the earth, so that they must have a succession of day and night as the earth does. •Some of them have moons that give them light in the absence of the sun, as our moon does to us. •The motions of all of them fall under the same law of gravitation as the earth does. From all this similarity, it isn’t unreasonable to think that those planets may, like our earth, be the homes of various orders of living creatures. There is some probability in this conclusion from analogy.

In medicine, physicians have to be guided by analogy in most of their prescriptions. The constitution of one human body is so like that of another that it’s reasonable to think that what causes health or sickness in one may have the same effect on another. And this is generally found true, though there are exceptions.

In politics we reason mostly from analogy. The constitution of human nature is so similar in different societies or commonwealths that the causes of peace and war, of tranquility and revolt, of riches and poverty, of improvement and deterioration, are much the same in all of them.

So analogical reasoning should not be rejected across the board. It can confer more or less probability depending on whether the things that are compared are more or less similar in their nature. But this kind of reasoning can provide only probability, at best; so unless great caution is used we are apt to be led into error by it, for men are naturally disposed to think that things are more alike that they really are.

Here is one example. Anatomists in ancient times seldom dissected human bodies, but often dissected the bodies of quadrupeds whose internal structure was thought to come closest to that of the human body. Modern anatomists have discovered many mistakes that the ancients were led into by thinking there was more anatomical similarity between men and some beasts than there really is. From this and many other examples that might be given, we can see that conclusions built on analogy stand on a slippery foundation, and that we ought never to rely on evidence of this kind in cases where we can have more direct evidence.

I know no author who has made a sounder and more satisfactory use of this kind of reasoning than Bishop Butler in his The Analogy of Religion, Natural and Revealed, to the Constitution and Course of Nature. In that excellent work the author doesn’t use analogy as evidence on which to base any of the truths of religion. He uses it only to answer objections against those truths. An objection against the truths of religion can’t have any weight if it holds just as strongly against what we know to be true in the course of Nature.

Thus, analogical reasoning can be extremely useful in answering objections against truths that have other evidence ·to support them·. And it can also confer large or small probabilities in cases where we can’t find other evidence. But all arguments from analogy are weak to the extent that the compared things are dissimilar; so they must be weakest of all when we compare body with mind, because no two things in Nature are more unalike than they are.

On no other subject have men been so prone to form their notions by analogies of this kind as they are in what concerns the mind. Our senses acquaint us with material things early in our lives, and we grow up in constant familiarity with them. This makes us apt to measure all things by them, and to ascribe the qualities of material things to things that are nothing like them. That is why mankind have always been so prone •to think of the mind itself as some subtle kind of matter; and •to ascribe human shape and human organs not only to angels but even to God. We are conscious of the operations of our own minds when they are going on, and we can attend to them so as to form a clear notion of them; but this is hard work for men whose attention is constantly being claimed by external objects. So hard that we give •our mental operations names taken from things that are familiar and are thought to have some similarity to •them; and the notions we form of them are just as analogical as the names we give them. Almost all the words by which we express the operations of the mind are borrowed from material objects. [In the following list, the words on the left are given by Reid; the explanations on the right are added.]

‘understand’—from ‘under’ and ‘stand’

‘conceive’—from Latin concipere = hold in the hand

‘imagine’—from Latin imago = portrait, painting, etc.

‘comprehend’—from Latin comprehendere = ‘hold in the hand’

‘deliberate’—from Latin librare = weigh

‘infer’—from Latin inferre = ‘bring in’

and many others are words of this kind; so that when it comes to the operations of our minds, the very language of mankind is analogical. Because bodies are affected only by contact and pressure, we are apt to think that whatever is an immediate object of thought, and affects the mind, must be in contact with it and make some impression on it. When we imagine something, the very word leads us to think that there must be in the mind some image—·some representation, like a portrait·—of the thing that is imagined. . . .

Analogical reasoning based on a supposed similarity of mind to body produces more errors about the operations of our minds ·than does anything else·. Here is another example of it.

When a man is urged by contrary motives, some of them inciting him to perform a certain action and others inciting him not to, he thinks about whether to do it—and eventually he either decides to do it or decides not to. These opposing motives are compared to the weights in the opposite scales of a balance; and this may be the most striking analogy there is between body and mind. That is why phrases like ‘weighing motives’ and ‘deliberating on actions’ occur in all languages.

Some philosophers draw very important conclusions from this analogy. They say:

•As a balance can’t slope either way when the opposite weights are equal, so a man can’t decide what to do if the motives on the two sides are equal. And

•As a balance has to go down on the side with most weight, so a man has to decide to perform the action for which the motive is strongest.

On this basis, some of the schoolmen maintained that if a hungry ass were placed between two equally inviting bundles of hay, the beast would have to stand still and starve to death, being unable to turn to either bale because there were equal motives to both! This is an example of the kind of analogical reasoning that I think should never be trusted; for the analogy between a balance and a man who is deliberating, though one of the strongest that can be found between matter and mind, is too weak to support any argument. A piece of dead inactive matter is very unlike an active thinking being, and because one would remain at rest in a certain case it doesn’t follow that the other would be inactive in a somewhat similar case. . . .

Chapter 5: The right way to get knowledge of the operations of the mind

‘If we ought to ignore hypotheses, and to be very suspicious of analogical reasoning, from what source can we get knowledge of the mind and its faculties?’ I answer that the main source for this branch of knowledge is careful reflection on the operations of our own minds. Before coming to a fuller treatment of this source, I shall offer some remarks about two other sources ·of knowledge about the mind· that may be subservient to it.

1. The first is attention to the structure of language. Men’s language expresses their thoughts and the various operations of their minds. The various •operations of the understanding, will, and passions, which are common to mankind, have in all languages corresponding •forms of speech, which are the signs of them and by which they are expressed. By paying due attention to these signs we may in many cases get considerable light on the things signified by them.

All languages have modes of speech by which men

say what they think,

give their testimony,

accept or refuse,

ask for information or advice,

command, threaten, or implore,

give their word in promises or contracts.

If such operations weren’t common to all mankind we wouldn’t find in all languages forms of speech by which they are expressed.

Of course all languages have imperfections; they can never be adequate to all the varieties of human thought; so it can happen that two things are really distinct in their nature, and can be so distinguished by the human mind, though they aren’t distinguished in common language. The most we can expect to find in the structure of languages are the distinctions that all mankind find a need for in the common business of life. [Reid goes on to emphasize that this is about what’s found in all languages, not any one particular language. Then:]

I have given some examples of this, and now add one more. All languages have •plural forms of many of their nouns; from which we can infer that all men have notions not only of individual things but also of attributes, i.e. things that are common to •many individuals. . . .

2. Another source of information about the human mind is a due attention to human actions and conduct. Men’s actions are •effects; their opinions, emotions and feelings are the •causes of those effects; and it is often all right for us to form a judgment about a cause from its effect.

The behaviour of parents towards their children gives sufficient evidence, even to those who never had children, that parental affection is common to mankind. It is easy to see from the general conduct of men what sorts of things they naturally look up to, admire, love, approve of, resent. . . and so on through all their natural dispositions. ·For example·, the conduct of men in all ages makes it obvious that man is by his nature a social animal—that he loves to associate with ·other members of· his species, to converse and exchange favours with them.

Not only men’s actions but even their opinions can sometimes throw light on the structure of the human mind. Men’s opinions of men can be seen as the effects of their •intellectual powers, just as their actions are the effects of their •active principles. [See on ‘principle’ here.] Even the prejudices and errors of mankind in general must have some equally general cause, the discovery of which will throw some light on the structure of the human understanding.

This, I think, is what the history of philosophy is chiefly useful for. When we trace the history of the various philosophical opinions that have sprung up among thinking men, we are led into a labyrinth of fanciful opinions, contradictions, and absurdities, mixed in with some truths; but sometimes we can find a thread to lead us through the various windings of this labyrinth. We may find the point of view from which the author of the system saw things; and this will often give a •consistency to things that looked •contradictory, and some degree of •probability to things that appeared most •fanciful.

The history of philosophy, considered as a map of the intellectual operations of men of genius, will always be interesting and may sometimes give us views of the human understanding which couldn’t easily be had any other way.

3. I return now to what I have said is the main source of information about the human mind, namely attentive reflection on the operations of our own minds.

Locke gave the label ‘ideas of reflection’ to all the notions we have of the mind and of its operations. A man can have notions of remembering, judgment, will and desire that are as clear as his notions of any object whatever. Such notions, as Locke rightly says, are acquired by the power of reflection. But what is this power of reflection? He answers that it is ‘the power by which the mind turns its view inward, and observes its own actions and operations’ (Essay I.i.8). He observes elsewhere that ‘the •understanding is like the •eye in this: while it makes us see and perceive all other things, it pays no attention to itself; and we need skill and hard work to set it at a distance and make it its own object’ (I.i.1). . . .

This power of the understanding to direct itself towards its own operations, to attend to them and examine them on all sides, is the power of reflection. It is the only way for you to have any clear notion of the powers of your own mind or of anyone else’s.

This •reflection ought to be distinguished from •consciousness, though they are often run together, even by Locke. All men are •conscious of the operations of their own minds at all times while they are awake; but there are few who •reflect on them or make them objects of thought.

Throughout our pre-adult lives we are engaged solely with external objects. The mind is •conscious of its operations ·through those years and beyond·, but it doesn’t •attend to them; its attention is directed solely onto the external objects that those operations are concerned with. An angry man is conscious of his anger, but his attention is directed towards the person who offended him and the circumstances of the offence, and not at all towards the passion of anger itself.

I think this is enough to show the difference between •consciousness of the operations of our minds and •reflection on them; and to show that we can have the •former without any degree of the •latter. The difference between consciousness and reflection is like the difference between •a superficial view of an object that presents itself to the eye when we are focussing on something else and •the attentive examination that we give to an object when we are wholly engaged in surveying it. Attention is voluntary: it requires active exertion to start attending to something, and to continue doing so; and we can go on attending for as long as we choose. But consciousness is involuntary, and it doesn’t stay steady through a period of time, but changes with every ·change in our· thought.

The power to reflect on the operations of their own minds doesn’t appear at all in children; to become capable of it they must reach a certain level of intellectual maturity. Of all the powers of the human mind, this one seems to be the last to come into play. Most men seem ·to go on being· incapable of acquiring it in any considerable degree. Like all our other powers, it is greatly improved by being used; and until a man gets the •habit of attending to the operations of his own mind, he can never have clear notions of them, or form any steady opinion concerning them. He has to borrow his opinions from others, his notions will muddled and unclear, and he can easily be led to swallow very gross absurdities. It takes time and hard work to acquire this •habit , even for those who begin it early, and whose natural talents are pretty well fitted for it; but it will become easier every day, and the advantage of having this habit is great. It will enable you to think with precision and accuracy about every subject, especially the more abstract subjects. You’ll be able to judge for yourself on many important points, while others must blindly follow a leader.

Chapter 6: The difficulty of attending to the operations of our own minds

Anyone wanting to make progress in the science of the mind needs to understand the difficulty of attending to our own mental operations, and to have an accurate idea of how difficult this is. That is to protect him against •expecting to succeed without taking trouble and working hard, and against •becoming discouraged by the thought that the obstacles to success are insuperable, and that no certain results can be achieved in this science. So I shall do my best to point out the causes of this difficulty, and the effects that have arisen from it, so that we can form a true judgment of both. ·On the causes of the difficulty I have five points to make·.

1. It is hard to give due attention to the operations of the mind because there are so many of them and they whip by so quickly. It’s well known that if very many objects are presented in quick succession, even to the eye, our memory and imagination run them together. We retain a confused notion of the whole, and a more confused one of the individual parts, especially if they are objects to which we have never before given particular attention. No succession can be faster than that of thought. While we are awake the mind is busy, continually passing from one thought to another and from one operation to another. The scene is constantly shifting. You’ll be aware of this if you try for just one minute to keep the same thought in your mind, not varying it or adding to it. You will find it impossible to keep the scene of your imagination fixed. Other objects will force their way in, and all you can do is to reject these intruders as quickly as possible, and return to your principal object.

2. In this exercise we go against habits that we acquired long ago and that have been reinforced by long unvaried practice. From infancy we have been accustomed to attending to objects of sense and only to them; and when confirmed habit has given sensible objects such a strong hold on our attention, it isn’t easy to make them let go. . . .

3. The operations of the mind, from their very nature,lead the mind to give its attention to something else. I’ll show later that our sensations •are natural signs, which •turn our attention to the things they signify; doing this so thoroughly that most of our sensations—and the most frequent and familiar of them—have no name in any language. In perception, memory, judgment, imagination, and reasoning there is an object distinct from the operation itself; and, while we are led by a strong impulse to attend to the object, the operation escapes our attention. Our emotions, affections, and all our active powers also have objects that engross our attention, diverting it from the emotion itself.

4. To this we may add a correct point of Hume’s (Treatise II.i.4), namely: When the mind is agitated by some emotion, as soon as we turn our attention from the object to the emotion itself, the emotion dies down or vanishes, and in that way escapes our scrutiny. This indeed is common to almost all operations of the mind: while an operation is going on, we are conscious of it but are attending not to it but to its object; and when the mind is drawn away from the object to attend to its own operation, the operation stops and so escapes our notice.

5. . . . .In order to discover the truth concerning the operations of the mind, it isn’t enough to give attention to them; one must also be able •to distinguish accurately their tiny differences, •to resolve and analyse complex operations into their simple ingredients, to •sort out the ambiguity of words (there’s more ambiguity in this science than in any other) and give the words the same precision that mathematical terms have. In fact,

•the same precision in the use of words,

•the same cool attention to tiny differences between things,

•the same talent for abstraction and analysing,

that equips a man for the study of mathematics is equally necessary in the science of the mind. The big difference between these two sciences is that the objects of mathematics are external to the mind, so that it’s much easier to attend to them and hold them steady in the imagination.

·So much for causes of the difficulty. Now for some of its effects·. . . . Most branches of science have been highly cultivated, either in ancient or in modern times, and brought to a considerable degree of perfection. But this one remains to this day in a very low state—still in its infancy, so to speak.

Every science invented by men must •start, and then •develop; and from various causes it can happen that one science reaches considerable maturity while another is still in its infancy. What shows that a science is mature is this:

It contains a system of principles, and conclusions drawn from them, that are so firmly established that among thinking and intelligent people there remains no doubt or dispute about them; so that those who come later can raise the superstructure higher but can’t ever overturn what is already built so as to begin on a new foundation.

Geometry seems to have been in its infancy at about the time of Thales and Pythagoras, because they are credited with having invented many of the elementary propositions on which the whole science is built. Euclid’s Elements, written a good while after Pythagoras, presents a system of geometry that deserves the name of ‘science’; and though great additions were made by Apollonius, Archimedes, Pappus and others among the ancients, and still greater ones by the moderns, yet what was laid down in Euclid’s Elements has never been set aside. It remains as the firm foundation of all future superstructures in that science.

Natural philosophy remained in its infant state for nearly two thousand years after geometry had acquired its adult shape. For natural philosophy seems not to have been built on a stable foundation or carried to any degree of maturity until the last century, when Sir Isaac Newton ·in 1687· had the merit of getting this branch of philosophy into the ·adult· shape of a science. (Until then the system of Descartes dominated the most enlightened part of Europe, but it was all hypothesis.) It needn’t surprise us if the philosophy of the human mind should be a century or two later in being brought to maturity.

Several modern writers have contributed greatly to natural philosophy, ·bringing it nearer to qualifying as a science·. For it to be entitled to the name ‘science’ perhaps it doesn’t now need much more than to be cleansed of certain hypotheses that have deceived some of the most acute writers on this subject, leading them into downright scepticism.

What the ancients presented us with concerning the mind and its operations was almost entirely taken not from careful reflection but from some conceived analogy between body and mind. And although the modern authors I named earlier have given more attention to the operations of their own minds, and in that way have made important discoveries, they have also retained some of the ancient analogical notions; this has made their discoveries less useful than they might have been, and has led to scepticism.

An error in the foundation of a building can weaken the whole structure, and the further the building is carried on the more apparent and the more threatening the fundamental error becomes. As in building, so in science. Something like this seems to have happened in our systems concerning the mind. The additions that have been made to them by modern discoveries, though very important in themselves, have thrown darkness and obscurity on the whole, and have led men to scepticism rather than to knowledge. This must come from some fundamental errors that haven’t been observed; it is to be hoped that when these are corrected, the ·modern· improvements will have their proper effect.

I shall note just one other effect of the difficulty of investigating the powers of the mind. It is the fact that there is no other department of human knowledge in which able authors have been so apt to blunder into strange paradoxes and even into gross absurdities. In modern writings about the mind we find:

•philosophers maintaining that there is no heat in the fire, no colour in the rainbow;

•the most serious philosophers, from Descartes down to Berkeley, rounding up arguments to prove the existence of a material world, and not finding any that will bear examination;

•Berkeley and Hume, the acutest metaphysicians of the age, maintaining that there is no such thing as matter in the universe—that sun, moon, and stars, the earth we inhabit, our own bodies and those of our friends, are only ideas in our minds and have no existence except in thought;

•Hume maintaining that •there is neither body nor mind—nothing in Nature except ideas and impressions, without any substance on which they are impressed;

•Hume maintaining that there is no certainty, indeed no probability, even in mathematical axioms.

When we consider such wild claims by many of the ablest writers, we may suspect that the whole thing is only a dream—a tangle of mental cobwebs. But remember that the more tightly and cleverly men reason from false principles, the more absurdities they will be led into. We can perhaps forgive the absurdities because of their service in bringing to light the false principles that generated them.

Chapter 7: Classifying the powers of the mind

The powers of the mind are so many, so various, and so interlinked and complicated in most of its operations, that no system of classification of them has ever been proposed that isn’t open to considerable objections. So I shall start with the general division that is the most common, into •powers of the understanding and •powers of the will.

Under ‘the will’ I bring our active powers, and all that lead to action or influence the mind to act—such as appetites, emotions, affections. Under ‘the understanding’ come our contemplative powers, by which we perceive objects, conceive or remember them, analyse or compound them, we judge and reason concerning them.

This general will/understanding dichotomy can help us to proceed more methodically in our subject, but we shouldn’t take it to imply that the operations that are ascribed to the understanding never involve any exercise of will, any activity. I don’t think there is any operation of the understanding in which the mind isn’t to some extent active. We have some command over our thoughts, and out of the many objects that present themselves to our senses, our memory, or our imagination, we can choose which ones to attend to. We can ·choose whether to· survey an object on this side or that, superficially or carefully, for a longer or a shorter time; so that our •contemplative powers are under the guidance and direction of the •active powers; and the •former never pursue their object without being led and directed, egged on or held back, by the •latter: And because the understanding is always to some extent directed by the will, mankind have ascribed some degree of activity to the mind in its intellectual operations, as well as in those that belong to the will, and have expressed them by active verbs such as ‘see’, ‘hear’, ‘judge’, ‘reason’ and the like.

And the will/understanding dichotomy shouldn’t be taken to imply that the operations ascribed to the will never involve the understanding. For in fact, just as the mind exerts some degree of activity even in the operations of understanding, so it is certain that there can be no act of will that isn’t accompanied by some act of understanding: the will must have an object, and that object must be apprehended or conceived in the understanding.

So we need to remember that in most if not all operations of the mind both faculties work together, and we classify an operation under whichever faculty—·whichever side of the will/understanding dichotomy·—plays the greater part in it.

The intellectual powers are commonly divided into •simple apprehension, •judgment, and •reasoning. As this division has in its favour the authority of antiquity and of very general acceptance, I oughtn’t to set it aside without giving any reason. So I shall briefly explain it and then give my reasons for adopting a different classification.

You can’t •judge concerning something unless you •apprehend it; and you can’t •reason concerning it unless you •apprehend it and make •judgments about it. So these three operations are not independent of one another. The second includes the first, and the third includes both the first and second; but the first can be exercised without either of the other two. That’s why it is called ‘simple apprehension’—i.e. apprehension not accompanied by any judgment about the object that is apprehended.

This simple apprehension of an object is, in common language, called ‘having a notion’ or ‘. . . a conception’ of the object, and recent authors called it ‘having an idea’ of it. It is expressed by a word (‘man’) or by a part of a proposition that doesn’t have the complex structure of a complete sentence (‘a man of fortune’). Such words ·or phrases·, taken by themselves, signify simple apprehensions. They don’t affirm or deny; they imply no judgment or opinion about the thing they signify; so they can’t be true or false.

The second operation in this trichotomy is judgment. Philosophers have said that in a judgment two objects of thought must be brought together, and some agreement or disagreement—or more generally some relation—discerned between them; and that this results in an opinion or belief concerning the relation that we discern. This operation is expressed in speech by a proposition in which some relation between the two things is affirmed or denied—as in saying ‘All men are fallible’.

Truth and falsehood are qualities that belong to judgment only—or to propositions in which judgment is expressed. Every judgment, every opinion, and every proposition is either true or false. But words that don’t affirm or deny anything can’t be either true or false, and that holds also for the simple apprehensions that such words signify.

The third operation is reasoning, in which we draw a conclusion from two or more judgments.

[In this next paragraph, Reid will use ‘compare’ in a sense that it has almost lost today, a sense in which to compare two things is just to bring them together in a single thought in order to see how they relate to one another. The relation doesn’t have to be similarity or dissimilarity.] This classification of our intellectual powers corresponds perfectly with the account that philosophers commonly give of the successive steps through which the mind acquires knowledge, namely: (1) By the senses or by other means the mind is provided with various simple apprehensions, notions or ideas. These are the materials that Nature gives it to work with; and from the simple ideas it gets from Nature it forms various other more complex ones. (2) By comparing its ideas and perceiving their agreements and disagreements, it forms its judgments. (3) From two or more judgments it draws conclusions by reasoning.

If all our knowledge is acquired through a procedure of this kind, the above threefold classification of the powers of understanding. . . .is the most natural and the most proper that can be devised. This •theory ·about the acquisition of knowledge· and this •classification are so closely connected that it’s hard to judge which of them has given rise to the other; certainly they must stand or fall together. But if some of our knowledge is not acquired through a process of that kind—if there are routes to knowledge other than comparing our ideas and perceiving their agreements and disagreements—there may very well be operations of the understanding that can’t be fitted into any of the three categories that I have presented.

Let us consider some of the most familiar operations of our minds, and see to which of the three they belong. I begin with consciousness. I know that I think, and this is the most certain bit of knowledge that I have. Am I given this certain knowledge by •simple apprehension? Surely not! Simple apprehension doesn’t affirm or deny. And you won’t say that •reasoning lets me know that I think. So it must be by •judgment, i.e. (according to the above account of judgment) perceiving the agreement between two ideas. What two ideas? They’ll have to be the idea of myself and the idea of thought, for ‘I’ and ‘think’ are the terms of the proposition ‘I think’. According to this account then, I first have the idea of myself and the idea of thought, and then by considering these two ideas together I perceive that I think.

I ask you: Is that how you come to be convinced that you think? It seems to me obvious that my conviction that I think isn’t acquired in this way; and from that I infer that either •consciousness is not judgment or •judgment is not rightly defined as ‘the perception of some agreement or disagreement between two ideas’.

The perception of an object by my senses is another operation of the understanding. Is it simple apprehension or judgment or reasoning? It is not •simple apprehension, because I am wholly convinced that the object exists—as convinced as if this had been demonstrated—·which implies that sense-perception involves something in the nature of belief, which simple apprehension never does·. It isn’t •judgment either, if ‘judgment’ means ‘bringing ideas together and perceiving their agreements or disagreements’. And it isn’t •reasoning, because there are creatures that can’t reason but can perceive.

I find the same difficulty in classifying memory in terms of the trichotomy.

There is no more fruitful source of •error in this branch of philosophy than classifications that are wrongly thought to be complete. To make a perfect job of dividing up any class of things, one needs to command a view of the whole class all at once; very often our minds are not capacious enough for this; and in those cases something that wasn’t in the philosopher’s view when he made his division is omitted ·from his classificatory scheme·. Such an omitted item gets into the classificatory scheme, which involves falsifying its real nature—hence, •error. This has been such a common a fault of philosophers that anyone wanting to avoid error ought to be suspicious of classificatory schemes—even ones of long standing and great authority—especially ones based on some theory that is open to question. In a subject that is imperfectly known we ought not to aim at perfectly complete classifications; rather, we should to leave room for whatever additions or alterations may be suggested later on when we get a better view of the whole subject.

So I shan’t try to enumerate all the powers of the human understanding. I merely list the ones that I propose to explain, namely:

1. The powers we have by means of our external senses.

2. Memory.

3. Conception.

4. The power to resolve and analyse complex objects, and to make complexes out of simpler objects.

5. Judging.

6. Reasoning.

7. Taste.

8. Moral Perception.

9. Consciousness.

[Items 1-7 are the topics of Essays 2-8, in the same order. At the end of the Essay (8) on topic 7, Reid says that he hasn’t discussed topic 8, moral perception, because it belongs under man’s active rather than his intellectual powers; and that Consciousness (the item he doesn’t number) is discussed fully enough in Essay 6, chapter 5, item (1).]

Chapter 8: Social operations of mind

There is another way of dividing up the powers of the mind that gets overlooked by writers on this subject, but ought not to be because it has a real basis in Nature. Some operations of our minds are in their very nature social, while others are solitary.

By ‘social operations’ I mean ones that necessarily presuppose communication with some other thinking being. A man could understand and will, apprehend and judge and reason, even if he knew of no thinking being in the universe except himself. But when he

asks for or receives information,

offers or receives testimony,

requests or gets a favour,

gives a command to his servant or gets one from a superior,

gives his word in a promise or contract,

these are acts of social interaction between thinking beings, and can’t occur in solitude. They presuppose understanding and will, but they also presuppose something additional to both of those, namely society with other thinking beings. These operations can be called ‘intellectual’—·and so fall within the scope of this book·—because only intellectual [= ‘thinking’] beings can perform them. But they are not simple apprehension, or judgment, or reasoning, or any combination of those.

[Reid repeats in more detail that questioning, promising and giving testimony are perfectly well understood acts of the mind, but ones that fall outside the trichotomy. Then:] When philosophers try to bring them within the confines of their classificatory schemes by analysing them, they find inexplicable mysteries and even contradictions, in them. (Many examples of this might be mentioned, but here is just one: Hume, Enquiry Concerning the Principles of Morals, the last long footnote in Section 3.)

Philosophers’ attempts to bring our •social operations into the common classificatory scheme are very like the attempts of some philosophers to analyse all our •social affections as certain forms of self-love. God intended us to be social beings, and for that purpose he has given us •social intellectual powers as well as •social affections. Both are basic aspects of our constitution, and it is just as natural to us to employ them as it is to employ the powers that are solitary and selfish.

Our social •intellectual operations, as well as our social •affections, appear very early in life, before we are capable of reasoning; yet •both presuppose a belief that there are other thinking beings. When a child asks its nurse a question, this act of his mind presupposes not only a desire to know the answer but also a belief that the nurse is a thinking being to whom he can communicate his thoughts and who can communicate her thoughts to him. How did he get this conviction so early? That is a question of some importance in the knowledge of the human mind, so it is worthy of the consideration of philosophers. But they seem to have given no attention either to this early conviction or to the operations of mind that presuppose it. I’ll return to this in due course.

All languages are equipped to express the social as well as the solitary operations of the mind. Indeed, it may be held that the basic and immediate purpose of language is to express the social operations. A man who had no interactions with other thinking beings would never think of language. . . . Once language has been learned, it can be useful even in our solitary meditations; clothing our thoughts with words gives us a firmer hold on them. But this wasn’t the original purpose of language, and the structure of every language shows that it isn’t meant solely for this purpose.

In every language, a question, a command, a promise, which are social acts, can be expressed as easily and as properly as can a judgment, which is a solitary act. The expression of the judgment has been honoured with a particular name—it is called a ‘proposition’—and philosophers have paid a lot of attention to it, analysing it into its elements of subject, predicate, and copula. All the variants on this basic kind of proposition, and the more complex propositions that are made up out of these, have been anxiously examined in many long books. The linguistic expression of a question, command, or promise is as capable of being analysed as a proposition is; but we don’t see this being attempted; we haven’t even given them a name different from the operations that they express.

[In this context as in many but not all others, Reid is using ‘proposition’ to mean what we mean by ‘assertoric sentence’. That last point of his means this:

(1) My judgment that grass is green is expressed in the proposition ‘Grass is green’.

(2) My question as to whether grass is green is expressed in the question ‘Is grass green?’

In (2) our only label for that sentence is also our label for the mental operation that the sentence expresses.]

Why have theory-builders laboured so anxiously to analyse our solitary operations, and given so little attention to the social ones? The only explanation I can find is this: in their classification of the mind’s operations the social operations have been omitted, and thereby pushed out of sight. . . .

Essay 2: The Powers we have by means of our External senses

Chapter 1: The organs of sense

Chapter 2: The impressions on the organs, nerves, and brain

Chapter 3: Hypotheses concerning the nerves and brain

Chapter 4: ·Three· false inferences from impressions on the organs etc.

Chapter 5: Perception

Chapter 6: What it is to account for a phenomenon in Nature

Chapter 7: What Malebranche believed about the perception of external objects

Chapter 8: The ‘common theory’, and the views of the Aristotelians and of Descartes

Chapter 9: Locke’s views

Chapter 10: Berkeley’s views

Chapter 11: Berkeley’s view about the nature of ideas

Chapter 12: Hume’s views

Chapter 13: Arnauld’s views

Chapter 14: Thoughts about the common theory of ideas

Chapter 15: Leibniz’s system

Chapter 16: Sensation

Chapter 17: Objects of perception, starting with primary and secondary qualities

Chapter 18: Other objects of perception

Chapter 19: Matter and space

Chapter 20: The evidence of the senses, and belief in general

Chapter 21: Improving the senses

Chapter 22: The deceptiveness of the senses

Chapter 1: The organs of sense

Of all the operations of our minds, the perception of external objects is the most familiar. When a person is still in his infancy, his senses come to maturity even though his other powers haven’t yet sprung up. We have them in common with brute animals, and they provide us with the objects about which our other powers are most often employed. We find it easy to attend to the operations of our senses; and because they are familiar we re-apply their names to other powers that are thought to resemble them—·for example, we say ‘I can see that that argument is invalid’·. These reasons give them a claim to be considered first.

The perception of external objects is one main link in the mysterious chain connecting the material world with the intellectual world. We shall find many things that we can’t explain in this operation—enough of them to convince us that we don’t know much about our own make-up, and that a complete understanding of our mental powers, and how they operate, is beyond the reach of our minds.

In perception there are impressions on the organs of sense, the nerves, and the brain—and by the laws of our nature these •impressions are followed by certain •operations of the mind. These •two things are apt to be confused with one another, but ought to be most carefully distinguished. Some philosophers have concluded—without good reason—that the impressions made on the body are the proper efficient cause of perception. [’Efficient cause’ means that you and I mean by ‘cause’. The adjective distinguishes this from other aspects of a thing that were also called ‘causes’ of it in senses that we no longer have for that word.] Others have concluded—also without reason—that impressions are made on the mind similar to those made on the body. From these ·two· mistakes many others have arisen. The wrong notions that men have rashly taken up concerning the senses have led to wrong notions about other powers that are conceived to resemble them. Especially recently, many important powers of mind have been called ‘internal senses’, because of their supposed resemblance to the external senses—for example the sense of beauty, the sense of harmony, the moral sense. And it is to be feared that errors about the external senses have led to similar errors concerning the ‘internal senses’, because of the ·supposed· analogy ·or similarity· between them. So it matters a good deal to have sound views about the external senses, ·not just because they are important in themselves, but also· so as to avoid errors in other parts of our study of the mind.

With this in mind, I’ll begin with some remarks about ·the physical aspects of perception—specifically· our •sense-organs, the •impressions that are made on them in perception, and •the nerves and •brain.

Our only way of perceiving any external object is through certain bodily organs that God has given us for that purpose. He gave us the powers of mind that he saw to be suitable for our condition and our rank in his creation, including power of perceiving many objects around us—the sun, moon and stars, the earth and sea, and a variety of animals, plants, and inanimate bodies. But our power of perceiving these objects is limited in various ways, especially in the fact that to perceive any external object we must have the organs of the various senses, and they must be in a sound and natural state. Many disorders of the eye cause total blindness; others reduce the power of vision without destroying it altogether; and the same holds for the organs of all the other senses.

We know all this so well from experience that it doesn’t need proof; but take note that we know it only from experience. The only reason we can give for it is that it is the will of our maker, ·God, that we should perceive only through healthy organs of sense·. No-one can show it to be impossible for God to have given us the power of perceiving external objects without such organs. We have reason to believe that •when ·after death· we put off our present bodies and all the organs belonging to them, our perceptive powers will become better rather than becoming worse or being destroyed; that •God perceives everything in a much more perfect way than we do, without bodily organs; and that •there are other created beings that have more perfect and more extensive powers of perception than ours, with no sense-organs such as the ones that we find necessary. . . .

If a man were shut up in a dark room so that he could see nothing except through one small hole in the shutter of a window—would he come to the conclusion that the hole was the cause of his seeing, and that it was impossible to see in any other way? If he had never ever seen except in this way, perhaps he would think so; but the conclusion would be rash and groundless. The truth would be that he sees because God has given him the power of seeing, and he sees only through this small hole because his power of seeing is blocked in every direction outside the perimeter of the hole.

Another necessary warning: don’t think that the •organ of perception is the •thing that does the perceiving. . . . The eye isn’t the thing that sees; it’s only the organ by which the person sees. The ear doesn’t hear; it is the organ by which the person hears; and so on through the rest.

A man can’t see the satellites of Jupiter except through by a telescope. Does that lead him to think that it is the telescope that sees those moons? Of course not! That would be absurd! Well, it is equally absurd to think that eyes see or that ears hear. The telescope is an artificial organ of sight, which doesn’t itself see. The eye is a natural organ of sight, by which we see; but it doesn’t itself see, any more than the artificial organ does.

The eye is a machine that is most admirably designed for refracting the rays of light, and forming clear pictures of objects on the retina; but it doesn’t see the object or the picture. An eye that has been removed from the head can still form the picture, but no vision results from that. Even when the eye is in its proper place and is perfectly healthy, we know that an obstruction in the optic nerve prevents vision, even though the eye has done the whole of its job.

This is really very obvious, but ·to be on the safe side· I shall offer one more supporting remark: If the faculty of seeing were in the eye, that of hearing in the ear, and so on with the other senses, this would imply that the thinking thing that I call myself is not one thing but many. ·One of us sees, another of us hears, a third tastes, and so on!· But this is contrary to everyone’s unshakeable belief ·about himself·. When I say ‘I see’, ‘I hear’, ‘I feel’, ‘I remember’, this implies that a single self does all these things. Might we say that •seeing done by one piece of matter, •hearing by another, and •feeling by a third feeling could add up to ·sensory intake by· a single percipient being? That would be just as absurd as to suppose that •my memory, •your imagination, and •someone else’s reason could add up to a single thinking being. . . .

Chapter 2: The impressions on the organs, nerves, and brain

A second law of our nature regarding perception is that we don’t perceive any object unless some impression is made on the organ of sense, either through contact with the object or through contact with some medium—·some intermediate thing·—that travels from the object to the organ. (·The first law of our nature regarding perception lays down that we can’t perceive external objects unless we have sense-organs in good working order·.)

In two of our senses—namely touch and taste—the object itself has to come into contact with the organ. In the other three the object is perceived at a distance, but still through some medium thing that makes an impression on the organ. The emissions from bodies drawn into the nostrils with the breath are the medium of smell; waves in the air are the medium of hearing; and rays of light passing from visible objects to the eye are the medium of sight. . . .

These are facts that we know from experience to hold universally and invariably, both in men and brute animals. They constitute a law of our nature, by which our powers of perceiving external objects are further limited and circumscribed—·further, that is, than they are by the first law of our nature·. And the only reason we can give for it is that God so chose it, knowing best what kinds and degrees of power are suited to our state. When we were in the womb our powers of perception were •more limited than they are now, and in a future state ·after death· they may be •less limited than they are now.

Another law of our nature: for us to perceive objects, the impressions made on our sense-organs must be communicated to the nerves and through them to the brain. This is perfectly known to those who know anything of anatomy.

The nerves are fine cords that pass from the brain (or from the spinal marrow, which is an extension of the brain) to all parts of the body, dividing into smaller branches as they go until at last they are too small to see. And we have found by experience that all the body’s movements, voluntary and involuntary, are performed by means of the nerves. When the nerves that serve a limb are cut or tightly tied, that leaves us with no more power to move that limb than if it had been amputated.

As well as nerves that serve the muscular movements there are others that serve the various senses; and just as without the former we can’t move a limb, so without the latter we can’t perceive anything.

God in his wisdom has made this train of machinery necessary for our perceiving objects. Various parts of the body collaborate in it, each with its own function:

•The object must make an impression on the sense-organ either immediately or through some medium.

•The organ is merely a medium through which an impression is made on the nerve.

•The nerve serves as a medium to make an impression on the brain.

Here the material part ·of the process involved in perception· ends—or anyway we can’t follow it any further—and all the rest ·of the process· is intellectual. [Then a short paragraph sketching the empirical evidence for the view that nerves and brain are required for perception. Then:]

So we have sufficient reason to conclude that in perception the object produces some change in the organ, which produces some change in the nerve, which produces some change in the brain. And we give the name ‘impression’ to those changes because we don’t have a better name to express in a general manner any change produced in a body by an external cause without specifying the nature of that change. Whether it’s pressure or attraction or repulsion or vibration or something unknown for which we have no name, still it can be called an ‘impression’. But philosophers have never been able to discover anything at all concerning what in detail happens in this change or impression. . . . God has seen fit to limit our power of perception so that we don’t perceive unless we undergo such impressions—and that’s all we know of the matter.

But we have reason to conclude that in general, just as the •impressions on the organs nerves and brain correspond exactly to the •nature and conditions of the objects by which they are made, so also our •perceptions and sensations correspond to those •impressions, and vary and they do in kind and in degree. ·And it follows from this that our •perceptions and sensations in perception correspond to the •nature of the external objects that are perceived·. If this were not so, the information we get through our senses would not only be incomplete (as of course it is) but would be deceptive—which we have no reason to think it is.

Chapter 3: Hypotheses concerning the nerves and brain

Anatomists tell us that although the two coatings that enclose a nerve (they derive from the coatings of the brain) are tough and elastic, the nerve itself is not at all tough, being almost like ·bone· marrow. But it has a fibrous texture, and can be divided and subdivided until its fibres are too fine for our senses to detect them. And just because we know so very little about the texture of the nerves, there is plenty of room left for those who want to amuse themselves conjecturing.

The ancients conjectured •that the fibres of the nerves are fine tubes filled with a very fine spirit or vapour which they called ‘animal spirits’; •that the brain is a gland that extracts the animal spirits from the finer part of the blood, stores them, and continuously replenishes them as they get used up; and •that these animal spirits are what enable the nerves to perform their functions. Descartes showed how—·according to this theory·—muscular motion, perception, memory and imagination are brought about by the movements of these animal spirits back and forth along the nerves. He described all this as clearly as if he had been an eye-witness of all those operations. But it happens that neither eyesight nor the most delicately done injections has shown the nerves to have a tubular structure, ·which they must have if they are to be the channels for animal spirits·. So everything that has been said about animal spirits through more than fifteen centuries is mere conjecture.

[A paragraph on a theory by ‘Dr Briggs, who was Newton’s master in anatomy’. Reid judges that this theory, according to which the nerves do their work by being twanged like guitar strings, is fairly negligible. He reports that it has been generally neglected. Then:]

Newton in all his philosophical writings [reminder: ‘philosophy’ here covers science as well] took great care to distinguish

•his doctrines that he claimed to prove by sound induction, from

•his conjectures that were to stand or fall depending on whether future experiments and observations should establish or refute them.

He expressed his conjectures in the form of questions, so that they wouldn’t be accepted as truths but would be enquired into and settled according to the evidence found for or against them. Those who mistake his questions for a part of his doctrine do him a great injustice, and pull him down to the level of the common herd of philosophers, who have in all ages adulterated philosophy by mixing •conjecture with •truth. . . . Among other questions this truly great philosopher proposed was this:

Is there an elastic medium—an ether—that is immensely finer and more fluid than air, and that pervades all bodies and is the cause of •gravitation, of the •refraction and reflection of the rays of light, of the •transmission of heat across regions that have no air in them, and of •many other phenomena?

In the 23rd query in his Optics he presents this question concerning the impressions made on the nerves and brain in perception:

Is vision brought about chiefly by the vibrations of this medium—·i.e. the ether·—that are caused at the back of the eye by the rays of light, and spread along the solid, uniform, light-transmitting fibres of the optic nerve? And is hearing brought about by the vibrations of this or some other medium that are aroused by the tremor of the air in the auditory nerves and spread along the solid and uniform fibres of those nerves? Similarly with regard to the other senses.

[Reid next sketches a few details of the work of David Hartley, whose view of these matters is essentially the one that Newton asked about. Then:] Dr Hartley presents his system to the world with a request to his readers

to expect nothing but hints and conjectures on difficult and obscure matters, and a sketch of the principal reasons and evidences concerning matters that are clear. I acknowledge that I won’t be able to carry out at all accurately the proper method of philosophising that has been recommended and followed by Newton. I will merely attempt a sketch for the benefit of future enquirers.

The modesty and caution of this seem to forbid any criticism of it. I am reluctant to criticise something that is proposed in this way and with such good intentions; but I shall make some remarks on the part of the system concerning the impressions made on the nerves and brain in perception. ·I have two reasons for this·. •The tendency of this system of vibrations is to make all the operations of the mind mere mechanism, depending ·only· on the laws of matter and motion; and •the system has been announced by its devotees as something that has in a way been demonstrated.

In general Dr Hartley’s work consists of a chain of propositions, with their proofs and corollaries, all in good order and in a scientific form. But a good proportion of them are, as he candidly admits, only conjectures and hints, and he mixes these in with the propositions that have been legitimately proved, without distinguishing one lot from the other. The entire set, including the corollaries he draws from them, constitute a system. A system of this kind is like a chain of with some very strong links and some very weak ones: the chain is only as strong as its weakest link, for if that fails the chain fails and the object that it has been holding up falls to the ground.

All through the centuries philosophy has been adulterated by hypotheses—i.e. by systems built partly on facts and largely on conjecture. It is a pity that a man of Dr Hartley’s knowledge and candour should have followed the herd in this fallacious book of his, after expressing his approval of the right method of philosophising pointed out by Bacon and Newton. Indeed, Newton considered it as a reproach when his system was called his ‘hypothesis’, and said scornfully ‘I don’t make hypotheses’ [Reid gives it in Latin]. And it is very strange that Dr Hartley doesn’t just follow such a method of philosophising himself, but directs others to follow it in their enquiries. . . .

When men claim to account for any of the operations of Nature, the causes they assign are good for nothing unless they satisfy the two conditions that Newton has taught us:

•They must really exist, and not be merely conjectured to exist, without proof.

•They must be sufficient to produce the effect.

[In this context ‘proof’ = ‘good evidence’.] ·Let us take these in turn, asking how Hartley’s theory looks in the light of them·.

·DO THEY REALLY EXIST?·

As to the existence of vibrations in the substance in the centre of the nerves and in the brain, the evidence produced ·by Hartley· consists of (1) an empirical claim about a certain phenomenon, (2) an argument for conjecturing that the scope of the phenomenon is wider than we have evidence for, and (3) a conclusion drawn from this. Specifically: (1) We observe that the sensations of seeing and hearing, and some sensations of touch, last for a short time ·after the impression from the object has ceased·. (2) Though there is no direct evidence that the sensations of taste and smell, or most of the sensations of touch, are like this, analogy would incline one to believe that they must resemble the sensations of sight and hearing in this respect. (3) Given the continuance of all our sensations ·after the object has ceased to act·, it follows that external objects cause vibrations in the substance of the nerves and brain; because vibration is the only kind of movement that can continue for any length of time ·after its cause has ceased·.

This is the chain of proof. Its first link is strong, being confirmed by experience; the second is very weak; and the third even weaker. Other kinds of motion besides vibration can have some continuance, for example rotation, bending or unbending of a spring, and perhaps others that we haven’t yet encountered. And in any case we don’t know that what is produced in the nerves ·in perception· is motion; perhaps it is pressure, attraction, repulsion, or something we don’t yet know. . . . So there is no proof of vibrations in the infinitesimal particles of the brain and nerves.

You might think that the existence of an elastic vibrating ether is on more solid ground, having the authority of Newton, ·though of course he spoke of it in connection with problems in physics, not the physiology of nerves·. But don’t forget that although this great man had formed conjectures about this ether nearly fifty years before he died, and through all that time had it in mind as something to be looked into, he seems never to have found any convincing proof of its existence, and right to the end of his life he thought it was a question whether there is such an ether or not. In the second edition of his Optics (1717—·ten years before Newton’s death·) he gives this warning to his readers: ‘Lest anyone should think that I include gravity among the essential properties of bodies, I have added one question concerning its cause; I repeat, a question, for I don’t regard it—·i.e. the theory of ether·—as established.’ If we have respect for the authority of Newton, then, we ought to regard the existence of ether as something not established by proof but waiting to be inquired into by experiments; and I have never heard that since Newton’s time any new evidence of its existence has been found.

But, says Dr Hartley, ‘supposing that there is no direct evidence for the existence of ether, still if it—·the ether theory·—serves to account for a great variety of phenomena, that will provide it with indirect supporting evidence,’ There has never been a hypothesis invented by a clever man that didn’t have this kind of evidence in its favour: Descartes’s ‘vortices’ serve to account for a great variety of phenomena— so do the sylphs and gnomes of Pope!

. . . .In his preface Dr Hartley declares his approval of the method of philosophising recommended and followed by Newton; but having first deviated from this method in his practice, he eventually faces the need to justify this deviation in theory, bring arguments in defence of a method diametrically opposite to it—·i.e. to the procedure advocated by Newton·. He writes: ‘I accept a key to a code as a true one when it explains the code completely.’ I answer: To find the key requires an understanding equal or superior to the understanding—·in our present case, God’s·—that made the cypher. . . .

The devotees of hypotheses have often been challenged to show one useful discovery in the works of Nature that was ever made in that way. If instances of this kind could be produced, we ought to conclude that Bacon and Newton have done great disservice to philosophy by what they said against hypotheses. But if no such instance can be produced, we must conclude with those great men that every system that purports to account for the phenomena of Nature by hypotheses or conjectures is spurious and illegitimate. . . .

Hartley tells us ‘that any hypothesis that has enough plausibility to explain a considerable number of facts helps us to •absorb these facts in proper order, to •bring new ones to light, and to •make crucial experiments for the sake of future enquirers’. Well, yes, let hypotheses be put to any of these uses as far as they can serve. Let them suggest experiments or direct our enquiries; but let sound induction alone govern our belief.

[Then two paragraphs in which Reid discusses Hartley’s point that an ancient and respectable mathematical procedure known as ‘the rule of false’ involves starting to solve a problem with a guess. Reid says that that’s all right in mathematics, where there are independent means of knowing for sure whether the right conclusion was reached, but that it is worthless in the context of natural science.— Then a paragraph saying that most scientists since Newton have accepted his views about how science should be done; Hartley has been on his own in this. Then:]

·DO THEY EXPLAIN THE PHENOMENA?·

Another demand that Newton makes of the causes of natural things assigned by philosophers is that they be sufficient to account for the phenomena. Dr Hartley contends that vibrations etc. in the substance in the centre of the nerves and in the brain can account for all our sensations and ideas—in short, for all the operations of our minds. Let us briefly consider how sufficient they are for that purpose.

It would be an injustice to this author to think of him as a materialist. He presents his views very openly, and we shouldn’t take him to believe anything that his words don’t express. He thinks his theory has the following consequence:

If matter can be endowed with the most simple kinds of sensation, then it can achieve all the thinking that the human mind does.

He thinks his theory overturns all the arguments that are usually brought for the immateriality of the soul—arguments from the fine-grained complexity of our internal senses and of our faculty of thought, ·which is argued to outstrip anything that a merely material system could do·. But he doesn’t undertake to settle whether matter can be endowed with sensation. He even acknowledges that matter and motion, however finely divided and reasoned on, are still only matter and motion, so that he doesn’t want to be interpreted as opposing the immateriality of the soul.

[Then a paragraph in which Reid says that although Hartley is not a materialist, he does contend that all the complexity of human thought and sensation can be matched, detail for detail, by complexities in the big and small vibrations— ‘vibrations and vibratiuncles’—in the nerves. Vibrations for our sensations, vibratiuncles for our ideas. Then:]

But how can we expect any proof of the connection between vibrations and thought when the existence of such vibrations hasn’t been proved? The proof of their •connection can’t be stronger than the proof of their •existence: the author acknowledges that we can’t infer the existence of the thoughts from the existence of the vibrations, and it is equally obvious that we can’t infer the existence of vibrations from the existence of our thoughts! The existence of both must be known before we can know that they are connected, and how. For the existence of our thoughts we have the evidence of consciousness—a kind of evidence that has never been called in question. But no proof has yet been brought of the existence of vibrations in the inner substance of the nerves and brain.

So the most we can expect from this hypothesis is that vibrations can have enough differences of kind and of degree to match the differences of kind and degree among the thoughts they are supposed to account for—the match being good enough to lead us to suspect that the vibrations are somehow connected with the thoughts. (·This concerns vibrations considered abstractly; it’s a thesis about what variety there can be among vibrations—not about what variety is empirically found in them·.) If the divisions and subdivisions of thought run parallel with the divisions and subdivisions of vibrations, that would give to the hypothesis that they are connected the sort of plausibility that we commonly expect even in a mere hypothesis.

But we don’t find even this. ·Indeed, there isn’t enough variety among vibrations to produce a match with even a small subset of mental events·. Set aside

•all the thoughts and operations that Dr Hartley labels as ‘ideas’ and thinks to be connected with little vibrations, and

•the perception of external objects, which he ·wrongly· counts as ‘sensations’, and

•the sensations properly so-called that accompany our emotions and affections;

and confine ourselves to

•the sensations that we have by means of our external senses;

·and still· we can’t see any correspondence between the variety we find in their kinds and degrees and the variety that can be supposed in vibrations. ·To see this, let us look in turn at the two sides of this supposed match or correspondence·.

We have five senses whose sensations are of totally different kinds; and within each of these kinds—except perhaps sensations of hearing—we have a variety of sensations which differ in kind and not merely in degree. Think how many •tastes and •smells there are that differ in kind from one another, each of them capable of all degrees of strength and weakness! Heat and cold, roughness and smoothness, hardness and softness, pain and pleasure, are different kinds of sensations, and each has an endless variety of degrees. Sounds have the qualities of shrill and low-pitched, with all the different degrees of each. Colours have many more varieties than we have names for. How shall we find varieties in vibrations corresponding to all this variety of sensations that we have merely by our five senses?

I know of only two qualities of vibrations in a uniform elastic medium. They may be •quick or slow in various degrees, and they may be •strong or weak in various degrees; but I can’t find any division of our sensations that will make them match with those divisions of vibrations. If our only sensations were ones of hearing, the theory would do well enough: sounds are either •shrill or low-pitched, which may correspond to •quick or slow vibrations; and they are •loud or soft, corresponding to •strong or weak vibrations. But that leaves us with no variety in vibrations corresponding to the enormous variety in the sensations we have by sight, smell, taste, and touch.

[Reid then sketches and criticises Hartley’s attempts to overcome this difficulty by supposing further differences among vibrations, ‘heaping conjecture on conjecture’. Then:]

Philosophers have to some extent accounted for our various sensations of sound by the vibrations of elastic air. But bear in mind that we know that (1) such vibrations really do exist, and (2) that they tally exactly with the most noticeable phenomena of sound. We can’t show how any vibration could produce the sensation of sound—this must be attributed to the will of God or to some altogether unknown cause. But we do know that as the vibration is strong or weak the sound is loud or soft, and that as the vibration is quick or slow the sound is shrill or low-pitched. We can point out

•the relations amongst synchronous vibrations that produce harmony or discord, and

•the relations amongst successive vibrations that produce melody.

And all this is not conjectured but proved by a sufficient induction. So this account of sounds is philosophical [here = ‘scientific’], though there may be many aspects of sounds that we can’t account for and whose causes remain hidden. The connections described in this branch of philosophy are the work of God, not the fanciful inventions of men.

If anything like this could be shown in accounting for all our sensations in terms of vibrations in the inner substance of the nerves and brain, it would deserve a place in sound philosophy. But •when we are told about vibrations in a substance that no-one could ever prove to have vibrations or to be capable of them, and •when such imaginary vibrations are said to account for all our sensations, though we can’t see that their variety of kind and degree corresponds to the variety of sensations, the ‘connections’ described in a system like that are the creatures of human imagination and not the work of God.

Light-rays make an impression on the optic nerves, but not on the auditory or olfactory nerves. Vibrations of the air make an impression on the auditory nerves, but not on the optic or the olfactory nerves. Emissions from bodies make an impression on the olfactory nerves, but not on the optic or auditory nerves. No-one has been able to give a shadow of reason for all this. For as long as that is the case, isn’t it better to •confess our ignorance of the nature of those impressions made on the nerves and brain in perception than to •gratify our pride by fancying ourselves to have knowledge that we don’t have, and to •adulterate philosophy with a spurious brood of hypotheses?

Chapter 4: ·Three· false inferences from impressions on the organs etc.

1. Some philosophers—ancient and modern—imagined that man is nothing but a piece of matter so intricately organised that the impressions of external objects produce in it sensation, perception, remembering, and all the other operations we are conscious of. This foolish opinion must have arisen from observing the constant connection that God has established between certain impressions made on our senses and our perception of the objects that make impression, from which they weakly inferred that those impressions were the proper efficient causes of the corresponding perception. [See note on ‘efficient’ here.]

But no reasoning is more fallacious than the inference that one thing must be the cause of another because the two are always conjoined. Day and night have been joined in a constant succession since the beginning of the world, but who is so foolish as to infer from this that day causes night or that night causes the following day? Really, there is nothing more ridiculous than to imagine that any motion or state of matter should produce thought.

‘I know of a telescope that is so exactly made that it has the power of seeing.’ ‘I know of a filing-cabinet that is built so elegantly that it has the power of memory.’ ‘I know of a machine that is so delicate that it feels pain when it is touched.’ Such absurdities are so shocking to common sense that even savages wouldn’t believe them; yet it is the same absurdity to think that the impressions of external objects on the machine of our bodies can be the real efficient cause of thought and perception. I shall now set this aside, as a notion too absurd to be reasoned about.

2. Another conclusion that many philosophers have drawn is that in perception an impression is made •on the mind as well as •on the organ nerves and brain. As I noted ·in Essay 1, chapter 1· [around the middle of item 10], Aristotle thought that the form or image of the perceived object enters through the sense-organ and strikes on the mind. Hume gives the name ‘impressions’ to all our perceptions, to all our sensations, and even to the objects that we perceive. Locke says very positively that the ideas of external objects are produced in our minds by impact, ‘that being the only way we can conceive bodies to operate in’ (Essay II.viii.11). (To be fair to Locke, I should say that he retracted this view in his first letter to the Bishop of Worcester, and promised in the next edition of his Essay to have that passage corrected; but it isn’t corrected in any of the subsequent editions I have seen; perhaps he forgot, or the printer was negligent.)

There is no prejudice more natural to man than to think of the mind as having some similarity to body in its operations. Thus, men have been prone to imagine that as bodies are started moving by some impulse or impression made on them by contiguous bodies, so also the mind is made to think and to perceive by some impression made on it or some impulse given to it by contiguous objects. . . . If we think of the mind as immaterial—and I think we have very strong proofs that it is—we’ll find it difficult to attach any meaning to ‘impressions made on the mind’.

[Reid then discusses the idiom involved in ‘I was there when it happened but it made no impression on my mind’. This is correct ordinary usage, he says, but:] it is evident from the way modern philosophers use ‘impression on my mind’ that they don’t mean merely to report my perceiving an object, but rather to explain how the perception came about. They think that the perceived object acts on the mind in some way similar to that in which one body acts on another by making an impression on it. The impression on the mind is thought of as something in which the mind is entirely passive, and has some effect produced in it by the object. But this is a hypothesis that contradicts the common sense of mankind and ought not to be accepted without proof.

When I look at the wall of my room, the wall doesn’t act—it can’t act. Perceiving it is an act or operation of mine. This is how mankind in general see the situation; that is made clear by the way perception is spoken of in all languages.

Common folk don’t worry about how they perceive objects; they say what they are conscious of, saying it in a perfectly proper manner. But philosophers are eager to know how we perceive objects; and, conceiving some similarity between •a body’s being put into motion and •a mind’s being made to perceive, they are led to think that just as •the body must receive some impulse to make it move so •the mind must receive some impulse or impression to make it perceive. This analogy seems to be confirmed by the fact that we perceive objects only when they make some impression on the organs of sense and on the nerves and brain; but bear in mind that it’s in the ·passive· nature of body that it can’t change its state except through some force’s being impressed on it. The nature of mind is different. Everything we know about the mind shows it to be in its nature living and active, and to have the power of perception in its constitution, though still within the limits set for it by the laws of Nature.

So it seems that the phrase ‘impression made on the mind by corporeal objects’ either •is a phrase with no clear meaning—a sheer misuse of the English language—or •is based on a hypothesis for which there is no proof. I agree that in perception an impression is made on the sense-organ and on the nerves and brain, but I don’t agree that the object makes any impression on the mind.

3. Another inference from the impressions made on the brain in perception has been adopted very generally by philosophers, though I think it has no solid foundation. It is that the impressions made on the brain create images— likenesses—of the object perceived, and that the mind, being located in the brain as its reception room, immediately perceives those images, and only through them does it perceive the external object. This view that we perceive external objects not immediately but through certain images of them conveyed by the senses seems •to be the oldest philosophical hypothesis we have on the subject of perception, and •to have kept its authority until now, with small variations.

As I noted earlier, Aristotle maintained that the ‘species’ or images or forms of external objects come from the object and are impressed on the mind. And what Aristotle said about his •immaterial ‘species’ or forms the followers of Democritus and Epicurus said about •thin films of subtle matter coming from the object.

Aristotle thought that every object of human understanding enters ·the mind· at first through the senses, and that the notions acquired through them are refined and spiritualized by the powers of the mind so that eventually they become objects of the most elevated and abstracted sciences. Plato on the other hand had a very low opinion of all the knowledge we get through the senses. He thought it didn’t deserve to be called ‘knowledge’, and couldn’t be a basis for science, because the objects of sense are mere individuals, and are in a constant state of change. All science, according to Plato, must concern the eternal and unchanging ideas that existed before the objects of sense and are not liable to any change. This marks an essential difference between the systems of these two philosophers: the notion of eternal unchanging ideas that Plato borrowed from the Pythagorean school was totally rejected by Aristotle, for whom it was a maxim, ·an axiom·, that there is nothing in the intellect that wasn’t at first in the senses.

Despite this big difference between those two ancient systems, they could both agree about how we perceive objects through our senses. And I think they probably did, because Aristotle, as far as I know, doesn’t note any difference between himself and his master on this point, and doesn’t claim that his theory about how we perceive objects is his own invention. It is made still more probable by Plato’s hints, in the seventh book of Republic, concerning how we perceive the objects of sense. He compares this to people in a deep and dark cave who don’t see external objects but only their shadows by a light let into the cave through a small opening. . . .

The ancients had a great variety of views about where the soul is located. Since advances in anatomy have led to the discovery that •the nerves are the instruments of perception and of the sensations that accompany it, and that •the nerves ultimately run to the brain, philosophers have generally held that the soul is •in the brain, and that it perceives the images that are brought •there, and perceives external things only by means of those images.

Descartes thought the soul must have one location; and he saw that the pineal gland is the only part of the brain that is single, all the other parts being double; which led him to make that gland the soul’s habitation, to which news is brought—by means of the animal spirits—concerning all the objects that affect the senses.

Others haven’t thought it right to confine the soul to the pineal gland, and have located it •in the brain in general or •in some part of it that they call the sensorium. Even the great Newton favoured this opinion, though he presents it only as a question, with the modesty that distinguished him as much as his great genius did:

Isn’t the sensorium of animals the place where the sensing substance is present, and to which the sensible species of things are brought through the nerves and brain so that they can be perceived by the mind that is present in that place? And isn’t there an immaterial, living, thinking, and omnipresent being, ·God·, who in infinite space (•as if it were his ·infinite· sensorium) intimately perceives things themselves and comprehends them perfectly because he is present to them—these being things of which our instrument of thought and perception discerns (•in its little sensorium) only the images ·or likenesses or sensible ‘species’· that the sense-organs bring to it?

His great friend Samuel Clarke adopted the same position with more confidence. In his letters to Leibniz we find the following:

Unless it is present to the images of the things that are perceived, the soul couldn’t possibly perceive them. A living substance can perceive a thing only when it is present either •to the thing itself (as omnipresent God is present to the whole universe) or •to the images of things (as the soul of man is in its own sensorium). A thing can’t •act or be acted on in a place where it isn’t present, any more that it can •exist in a place where it isn’t present. (Clarke’s second reply. . . .)

[Reid then gives evidence of Locke’s also holding that we perceive things through images of them that enter the brain, the mind’s reception room. Then:] But whether he thought with Descartes and Newton that the images in the brain are perceived by the mind that is present there, or rather that they are imprinted on the mind itself, is not so evident.

This hypothesis stands on three legs, and if any one of them fails the hypothesis must fall to the ground: (1) The soul has its location—or as Locke calls it, its reception room—in the brain. (2) Images of all the objects of sense are formed in the brain. (3) The mind or soul perceives these images in the brain, and perceives external objects not immediately but only by means of those images. ·I shall discuss these in turn·.

(1) ‘The soul is located in the brain’—this is surely not so well established that we can safely build other principles on it! There have been various opinions and much disputation about the location of spirits—do they have a location at all? if they do, how do they occupy it? After men had for centuries fumbled in the dark regarding those questions, the wiser of them seem to have dropped the questions because these matters are beyond the reach of the human faculties.

(2) ‘Images of all the objects of sense are formed in the brain’—I venture to assert that there is no proof or even probability of this with regard to any of the objects of sense, and that with regard to most of them it is downright meaningless.

·NO PROOF OR PROBABILITY·

We haven’t the faintest evidence that an image of any external object is formed in the brain. The brain has been dissected countless times by the most careful and precise anatomists; every part of it has been examined by the naked eye and with the help of microscopes; but no trace of an image of any external object has ever been found. The brain is a soft, moist, spongy substance, which makes it utterly unsuitable for receiving or retaining images.

Anyway, how are these images formed? Where do they come from? Locke says that the sense-organs and nerves bring them in from outside the body. This is just the Aristotelian hypothesis of ‘sensible species’, which modern philosophers have taken trouble to refute and which must be admitted to be one of the least intelligible parts of the Aristotelian system. Those who think that

•·Aristotelian sensible· species of colour, shape, sound, and smell coming from the object and entering by the sense-organs

are part of the scholastic jargon that was discarded from sound philosophy long ago ought to have discarded

•images in the brain

along with them. No author has ever produced a shadow of argument to show that any image of an external object ever entered the brain through any sense-organ.

External objects do make some impression on the organs of sense and through them on the nerves and brain, but it is most improbable that those impressions resemble the objects that make them and thus count as ‘images’ of those objects. Every hypothesis that has been contrived shows that there can’t be any such resemblance: it can’t be supposed that

the motions of animal spirits,

the vibrations of elastic cords,

the vibrations of elastic ether, or

the vibrations of the tiny particles of the nerves

resemble the objects that cause them. We know that in vision an image—·properly so-called, i.e. a likeness·—of the visible object is formed at the bottom of the eye by the light-rays. But we also know that this image can’t be conveyed to the brain, because the optic nerve and all the parts that surround it are opaque, and don’t allow light-rays through. And in no other organ of sense is any image of the object formed, ·let alone conveyed to the brain·.

·MEANINGLESS·

With regard to some objects of the senses we can understand what is meant by ‘an image of the object imprinted on the brain’; but with regard to most objects of the senses that phrase is absolutely unintelligible and has no meaning at all. As regards an object of sight: I understand what is meant by ‘an image of its shape in the brain’, but how am I to make sense of ‘an image of its colour’ in the brain where there is absolute darkness? And as for all objects of sense other than shape and colour, I can’t conceive what ‘an image of’ them could mean. I challenge anyone to say what he means by ‘an image of heat’, ‘. . . of cold’, ‘. . . of hardness’, ‘. . . of softness’, ‘. . . of sound’, ‘. . . of smell’, ‘. . . . of taste’. The word ‘image’ when applied to these objects of sense has absolutely no meaning. What a weak foundation there is, then, for this hypothesis that images of all the objects of sense are imprinted on the brain, having been carried to it along the channels of the organs and nerves!

(3) ‘The mind perceives the images in the brain, and perceives external objects only by means of them’—this is as improbable as the thesis that there are such images to be perceived. If our powers of perception are not totally untruthful, the objects we perceive are not in our brain but in our environment. So far from perceiving images in the brain, we don’t perceive our brain at all. If anatomists hadn’t done dissections, no-one would even know that he had a brain.

[Then two paragraphs summing up the findings of this chapter.]

Chapter 5: Perception

When we speak of the impressions made on our organs in perception, we are relying on facts taken from anatomy and physiology—facts for which we have the testimony of our senses. But now we are to speak of perception itself, ·not merely something that happens in perception·. And perception is solely an act of the mind, so we must appeal to some authority other than anatomy and physiology. The operations of our minds are known not through the senses but by consciousness, the authority of which is as certain and as irresistible as that of the senses.

Everyone is conscious of the operations of his own mind; for us to have a clear notion of any of those operations of our own minds we need more than mere consciousness. We also have to •attend to them while they are going on, and •reflect on them carefully when they are recent and fresh in our memory; and we need to do this often enough for us to get the habit of this sort of attention and reflection. Thus, when I make some factual claim on this topic, I can only appeal to your thoughts, asking whether my claims don’t square with what you are conscious of in your own mind.

Well, now, if we attend to the act of our mind that we call ‘perceiving an external object of sense’ we shall find in it these three things: (1) Some conception or notion of the object perceived. (2) A strong and irresistible conviction and belief that the object does at present exist. (3) That this conviction and belief are immediate, and not upshots of reasoning. ·I shall discuss these in turn·.

(1) It is impossible to perceive an object without having some notion or conception of the thing we perceive. We can indeed conceive an object that we don’t perceive; but when we perceive the object we must have some conception of it at the same time, and usually we have a clearer and steadier notion of the object while we perceive it than we get from memory or imagination at a time when we aren’t perceiving it. Yet even during perception the notion our senses give us of the object may be extremely clear, extremely unclear, or something in between.

[Reid then comments on the variations in how well we see something, depending on distance, light conditions, naked eye versus microscope, and so on. He says that all this can easily be re-applied to the other senses, and that this is obvious to anyone who can reflect at all. Then:]

I need only add that the notion we get of an object merely by our external sense mustn’t be confused with the more scientific notion that an adult may have of the same object by attending to its various attributes, or to its various parts and their relation to each other and to the whole. Thus the notion that a child has of a mechanical spit for roasting meat will obviously be very different from that of a man who understands the thing’s construction and perceives how its parts relate to one another and to the whole thing. The child sees the apparatus and every part of it as well as the man does, so the child has all the notion of it that sight can give; and whatever else there is in the adult’s notion of the apparatus must be derived ·not from sight but· from other powers of the mind. . . . We should be careful not to run together the operations of different powers of the mind—powers that are apt to be taken as one and the same because in our adult years they are always conjoined.

(2) In perception we have not only a more or less clear •notion of the perceived object but also an irresistible •belief that it exists. This is always the case when we are sure that we perceive it. A perception can be so faint and indistinct that we aren’t sure whether we perceive the object or not. For example, when a star begins to twinkle as the light of the sun fades, you may for a short time •think you see it without •being sure that you do, until the perception acquires some strength and steadiness. . . . But when the perception is in any degree clear and steady, there remains no doubt of its reality, in which case the existence of the perceived object is also past doubt.

[Reid then says that in every country’s law-courts witnesses may be challenged as liars, but never on the grounds that ‘the testimony of their eyes and ears’ shouldn’t be trusted. If any counsel ‘dared to offer such an argument. . . .it would be rejected with disdain’. Then:] There couldn’t be stronger proof that it is the universal judgment of mankind that

the evidence of the senses is a kind of evidence that we can safely depend on in the most momentous concerns of mankind, a kind of evidence against which we ought not to allow any reasoning; and therefore to reason against it—or to reason for it—is an insult to common sense.

The whole conduct of mankind in everyday life, as well as in the solemn procedure of courts in the trial of civil and criminal cases, demonstrates this. I know only of two exceptions that may be offered against this being the universal belief of mankind.

The first exception is that of some lunatics who become convinced of things that seem to contradict the clear testimony of their senses—e.g. one who seriously believed he was made of glass, and lived in continual terror of breaking. Well, our minds as well as our bodies are—in our present ·earthly· state—liable to strange disorders; and just as we don’t judge concerning the natural constitution of the •body from the disorders or diseases that may come its way, so we oughtn’t to judge concerning the natural powers of the •mind on the basis of its disorders rather than from its sound state. . . . It is natural for man to have faculties superior to those of brutes; yet we see some individuals whose faculties are not equal to those of many brutes; and the wisest man can by various accidents be reduced to this state. General rules about those whose intellects are sound are not overthrown by instances of men whose intellects are not sound.

The other exception is that created by some philosophers who have maintained that the testimony of the senses is deceptive and therefore should never be trusted. Perhaps it is a sufficient answer to this to say that there’s nothing so absurd that no philosophers have maintained it! It is one thing to proclaim a doctrine of this kind, another seriously to believe it and live by it. Obviously a man who didn’t believe his senses couldn’t keep out of harm’s way for an hour; yet in all the history of philosophy we never read of any sceptic who walked into fire or water because he didn’t believe his senses!. . . . We are entitled to think that philosophy was never able to conquer men’s natural belief in their senses, and that sceptical philosophers, in all their subtle reasonings against this belief, were never able to persuade themselves.

So it appears that the clear and distinct testimony of our senses carries irresistible conviction along with it to every man who is in his right mind.

(3) This conviction is not only irresistible but is immediate. It is not by reasoning and argumentation that we come to be convinced of the existence of what we perceive; the only argument we want for the object’s existence is that we perceive it. Perception commands our belief on its own authority, and doesn’t condescend to base its authority on any reasoning whatsoever.

·Don’t think that point (3) follows from point (2), because it doesn’t·. A belief can irresistible without being immediate. For example, my conviction that the three angles of every plane triangle are equal to two right angles is irresistible, but it isn’t immediate: I am convinced of it ·only· by demonstrative reasoning. There are other truths in mathematics of which we have a conviction that is not only irresistible but also immediate. The axioms are like that. Our belief in the axioms of mathematics isn’t based on argument. Arguments are based on the axioms, but their evidentness is discerned immediately by the human understanding.

It is one thing to have an immediate conviction of a self-evident axiom, and another thing to have an immediate conviction of the existence of what we see. But the conviction is equally immediate and equally irresistible in both cases. No man thinks of looking for reasons to believe in what he sees; and we trust our senses just as much before we are capable of reasoning as we do afterwards. . . . The constitution of our •understanding causes us to accept the truth of a mathematical axiom, regarding it as a first principle from which other truths can be deduced but isn’t itself deduced from anything; and the constitution of our •power of perception causes us to accept the existence of what we clearly perceive, regarding it as a first principle from which other truths can be deduced but isn’t itself deduced from anything.

[All this, Reid says, holds only for adults. Children don’t have a clear line between what is imagined and what is perceived, and anyway they may be incapable of having any notion as abstract as that of existence. Then:]

The account I have given of our perception of external objects is intended as a faithful portrayal of what every adult man who is capable of attending to what passes in his own mind can feel in himself. How do our senses produce the notion of external objects and the immediate belief in their existence? I can’t tell you, and I don’t claim to be able to do so. If the power of perceiving external objects in certain circumstances is a part of the original constitution of the human mind—·part of its basic design·—then all attempts to account for it will be vain. The only explanation we can give for the constitution of things is ‘They are like that because God willed that they should be so’. Just as we can give no reason why matter is extended and inert, why the mind thinks and is conscious of its thoughts, except ‘That was the choice of God, who made both matter and mind’. . . .

God intended us to have such knowledge of the material objects that surround us as we need for supplying our natural wants and avoiding the dangers to which we are constantly exposed; and he has admirably fitted our powers of perception to this purpose. If the news we get about external objects could be acquired only through reasoning, the majority of men wouldn’t have it; for the majority hardly ever learn to reason; and in infancy and childhood no-one can reason. . . . So God in his wisdom conveys news of external objects to us in a way that puts us all on a level. The information of the senses is as perfect, and gives as full conviction, to the most ignorant as to the most learned.

Chapter 6: What it is to account for a phenomenon in Nature

Here is a fact that everyone knows:

If an object is placed at a proper distance from you, and in good light, while your eyes are shut, you won’t perceive it at all. But the moment you open your eyes you have—as though by inspiration—certain knowledge of the object’s existence, of its colour and shape, and of how far away it is.

Ordinary folk are satisfied with knowing this fact, and don’t trouble themselves about the cause of it. But a philosopher is impatient to know how this event comes about, to account for it, to assign its cause.

This eagerness to know the causes of things is the parent of all philosophy, true and false. For theoretically minded men, such knowledge is a large part of happiness!. . . . But just as men often go astray when pursuing other kinds of happiness, so do they also—as often as anywhere—in the philosophical pursuit of the causes of things.

Common sense tells us that the causes we assign to appearances ought to be real, not fictions of human imagination. It is also self-evident that such causes ought to be adequate to the effects that are thought to be produced by them. [These are the two parts of Newton’s ‘first rule of philosophising’, introduced here.]

If you are not very familiar with inquiries into the causes of natural appearances, I shall try to give you a better understanding what it is to •show the cause of such appearances, or to •account for them. I’ll do this in terms of a plain example of a phenomenon or appearance of which a full and satisfactory account has been given, namely:

A stone or any heavy body falling from a height continually speeds up as it falls; so that if it reaches a certain velocity in one second of time, it will be going twice as fast as that at the end of two seconds, three times as fast at the end of three seconds, and so on in proportion to the time.

This accelerated velocity in a falling stone must have been •observed from the beginning of the world; but as far as we know the first person who •accounted for it in a proper and philosophical manner—after countless false and fictitious accounts had been given of it—was the famous Galileo.

He observed that once a body has been started moving, it will continue to move at that speed and in that direction until it is stopped or slowed down ·or speeded up· or diverted by some force impressed on it. This property of bodies is called their ‘inertia’, which is Latin for ‘inactivity’; because all it amounts to is that bodies can’t unaided change their state from rest to motion or from motion to rest. Galileo also observed that gravity acts constantly and equally on a body, and therefore will add equal amounts of speed to a body in equal times. From these principles, which are known from experience to be fixed laws of Nature, he showed that heavy bodies must descend with a uniformly accelerating speed, as experience shows them to do. ·Here is how his reasoning went·:

Suppose that the gravitation [here = ‘weight’] of a falling body gives it velocity V at the end of one second. If at that moment its gravitation •stopped, the body would go on falling with velocity V. But in fact its gravitation •continues, and will in another second give it an additional velocity equal to V that it gave in the first second; so that the whole velocity at the end of two seconds will be 2V. And again, through the third second of the fall, 2V will continue while gravitation adds a further V, so that at the end of the third second the velocity will be 3V, and so on, indefinitely.

Notice that two causes are assigned for this phenomenon: (1) Bodies once put in motion retain their velocity and direction until it is changed by some force impressed on them. (2) The weight or gravitation of a body is always the same. These are laws of Nature confirmed by universal experience, so they are true causes, not invented ones. Also, they are precisely adequate to the effect ascribed to them; they must produce just exactly the motion that experience shows us falling bodies have—neither more nor less. The account given of this phenomenon is sound and philosophical; no other account will ever be required, or accepted, by people who understand this one.

Notice also that the causes assigned for this phenomenon are things of which we can’t assign a cause in their turn. Why do bodies once put in motion continue to move? Why do bodies constantly gravitate towards the earth with the same force? No-one has been able to answer either question. These are facts confirmed by universal experience, and no doubt they have a cause; but their cause is unknown, and we call them ‘laws of Nature’ because the only cause of them that we know is the will of God.

‘Can’t we try to find the cause of gravitation, and of other phenomena that we call “laws of Nature”?’ Of course we can! We don’t know what limit has been set to human knowledge, and there’s no such thing as going too far in our search for knowledge of the works of God. But ·don’t lose sight of what is involved in going one step back up the causal chain·. One might, for instance, hope to account for gravitation by an ethereal elastic medium; but to do this one must prove (1) that this medium does exist and is elastic, and (2) that this medium must necessarily produce the gravitation that bodies are known to have. Until these two things have been done, gravitation is not accounted for and its cause is not known; and when they are done, the elasticity of this ethereal medium will be considered as a law of Nature whose cause is unknown. ·The title ‘law of Nature’ will be lost by the gravitation of bodies, and picked up by the elasticity of the ether·. The chain of natural causes has aptly been compared to a chain hanging down from heaven: a link is discovered that supports the links below it, but it must be supported in its turn; and what supports it must also be supported. . . ·and so on· until we come to the first link, which is supported by the throne of ·God· the almighty. Every natural cause must have a cause, until we ascend to the first cause. And that is uncaused, and operates not by necessity but by will—·meaning that God acts as he chooses to, not as he must·. . . .

Chapter 7: What Malebranche believed about the perception of external objects

‘How does the thinking agent within us keep in step with the material world outside us?’ This has always been found a very difficult problem for the philosophers who think they have to account for every phenomenon in Nature. Many philosophers, ancient and modern, have racked their brains trying to discover what makes us perceive external objects through our senses. And there seems to be great uniformity in their main views, though with variations in the details.

Here is how Plato illustrates our way of perceiving the objects of sense. He supposes a dark underground cave in which men lie, tied up in such a way that they look only towards one part of the cave. Far behind there is a light, some rays of which come over a wall to the part of the cave that the prisoners can see. A number of people going about their business pass between them and the light, and the prisoners see their shadows but not the people themselves. [Reid goes on to say that Plato probably got his ideas about perception from Pythagoras, and that Aristotle’s views on this are probably a version of Plato’s. Then:] The •shadows of Plato may very well represent the •species and phantasms of the Aristotelian school and the •ideas and impressions of modern philosophers.

Two thousand years after Plato, Locke. . . .represents our way of perceiving external objects by an image very like that of the cave:

The understanding strikes me as being like a closet that is wholly sealed against light, with only some little openings left to let in external visible resemblances or ideas of things outside. If the pictures coming into such a dark room stayed there, and lay in order so that they could be found again when needed, it would very much resemble the understanding of a man, as far as objects of sight and the ideas of them are concerned. (Essay II.xi.17)

Plato’s cave and Locke’s closet can easily be made the vehicles for every theory of perception that has been invented. For they all presuppose that we don’t perceive external objects immediately, and that the immediate objects of perception are only certain shadows of the external objects. Those shadows or images. . . .were by the ancients called ‘species’, ‘forms’, ‘phantasms’. Since the time of Descartes they have commonly been called ‘ideas’, and by Hume ‘impressions’. But all philosophers from Plato to Hume agree that we don’t perceive external objects immediately, and that the immediate object of perception must be some image that is present to the mind. There seems here to be a unanimity rarely to be found among philosophers on such abstruse points!

‘According to the opinion of these philosophers, do we perceive only the images or ideas, and infer from them the existence and qualities of the external object? Or do they rather hold that we really perceive the external object as well as its image?’ The answer to this question is not quite obvious.

On the one hand, philosophers—except Berkeley and Hume—believe in the existence of external objects of sense, and call them objects of perception though not immediate objects. But what they mean by a ‘mediate object of perception’ I don’t find clearly explained. I am left wondering whether

they are suiting their language to popular opinion, and mean merely that we ‘perceive external objects’ in the figurative sense in which we say that we ‘perceive an absent friend’ when we look at a picture of him,

or whether instead

they mean that really and literally we perceive both the external object and the idea of it in the mind.

In the latter case, it would follow that in every case of perception a double object is perceived—for instance that I perceive one sun in the heavens and another in my own mind. I don’t find any of these philosophers saying this, however; and as it contradicts the experience of all mankind, I shan’t impute it to them.

So it seems that •they hold that we don’t really perceive the external object, but only the internal one; and that •when they speak of ‘perceiving external objects’ they mean this only in a popular or in a figurative sense as above explained. I have given one reason for thinking this to be the opinion of the philosophers in question. Here are three more: (1) If we really do perceive the external object itself, there seems to be no need—no use—for an image of it. (2) Since the time of Descartes, philosophers have generally thought that the existence of external objects of sense needs to be proved, and can only be proved from the existence of their ideas. (3) The way in which philosophers speak of ideas seems to imply that they are the only objects of perception.

Having tried to explain what is •common to philosophers in accounting for our perception of external objects, I shall give some details concerning their •differences. ·That will occupy this chapter and the next eight·.

The ideas by which we perceive external objects are said by some to be •God’s ideas; but most have thought that every man’s ideas are •his own, and are either in his mind or in his sensorium—·the part of the brain· where the mind is immediately present. The former view is the theory of Malebranche; I shall call the latter ‘the common theory’. [Malebranche died about 70 years before this work appeared. Reid’s discussions of other philosophers’ theories of perception will run until chapter 16.]

·LEADING UP TO MALEBRANCHE·

Malebranche’s theory seems to have something in common with the Platonic notion of ideas, but it isn’t the same. Plato believed that there are three eternal basic sources from which all things have their origin:

matter, ideas, and an efficient cause.

Matter is what all things are made of, and the ancient philosophers thought it was eternal. Ideas are forms, without matter, of every kind of thing that can exist; and Plato thought that these too were eternal and unchanging, and that they were the models or patterns on the basis of which the efficient cause, namely God, formed every part of this universe. These ideas were thought to be the sole objects of science, and indeed of all true knowledge. While we are imprisoned in the body, we are apt to attend only to the objects of sense; but these—being. . . .shadows rather than realities—can’t be the object of real knowledge. All science is concerned not with individual things, but with things that are universal and thought of in abstraction from matter. Truth is eternal and unchanging, and must therefore have eternal and unchanging ideas as its object. We, even in our present state, can contemplate ideas in some degree, but not without a certain purification of mind and abstraction from the objects of sense. Those, as far as I can understand them, were the lofty notions of Plato and probably of Pythagoras.

The philosophers of the Alexandrian school, commonly called the later Platonists, seem to have adopted the same system with one difference: they held that the eternal ideas are not a source distinct from God, but rather are in God’s intellect as the objects of the conceptions that his divine mind must have had from all eternity—not only of everything he has made but also of every possible existence, and of all the relations between things. By suitably purifying our minds and abstracting from the objects of sense, we may be in some measure ·not merely put in touch with ideas, but· united to God, becoming able in his eternal light to discern the most sublime intellectual truths.

These Platonic notions, grafted onto Christianity, probably gave rise to the sect of the ‘mystics’. Although this in its spirit and principles is extremely opposite to the Aristotelian system, it has never been extinguished and survives to this day.

Many of the Fathers of the Christian church—Augustine, for one—have a touch of the doctrines of the Alexandrian ·or later Platonist· school. But as far as I know that neither Plato nor the later Platonists nor St Augustine nor the mystics thought that we perceive the objects of sense in God’s ideas. They had too low a view of our perception of sensible objects to credit it with having such a high origin!

·ARRIVING AT MALEBRANCHE·

So the theory that we perceive the objects of sense in God’s ideas I take to be the invention of Father Malebranche himself. He cites many passages of St Augustine in support of it, and seems very anxious to have that Father of the Church in his camp. But although in those passages Augustine speaks of God’s being the ‘light of our minds’, of our being ‘illuminated immediately by the eternal light’, and uses other such elevated expressions, still he seems to apply those expressions only to our illumination in moral and divine matters, not to the perception of objects by the senses. . . .

Malebranche, with a very penetrating intellect, undertook a more detailed examination of the powers of the human mind than anyone before him. He had the advantage of the discoveries made by Descartes, whom he followed but not uncritically.

He lays it down as a principle accepted by all philosophers and not open to question that we perceive external objects not •immediately but •by means of images or ideas of them that are present to the mind:

Everyone will grant, I suppose, that we don’t perceive objects external to us immediately and of themselves. We see the sun, the stars, and countless ·other· objects external to us; and it’s very unlikely that the soul ventures to leave the body and stroll (as it were) through the heavens to contemplate all those objects ·immediately·. . . . The immediate object of the mind when it sees the sun, for example, is not •the sun but •something intimately united to the soul; and that is what I call an ‘idea’. So what I mean by ‘idea’ is just ‘whatever it is that is the immediate object, or nearest to the mind, when we perceive any object’. It should be carefully noted that for the mind to perceive any object it must have the idea of that object actually present to it. It’s not possible to doubt this. The things the soul perceives are of two kinds: those in the soul, and those external to it. The ones in the soul are its own thoughts, i.e. its various states and events. The soul doesn’t need ideas to perceive these things. But with regard to things external to the soul, we can’t perceive them except by means of ideas. (The Search After Truth, start of Book 3, Part 2, chapter 1)

Having laid this foundation, as a principle accepted by all philosophers and admitting of no doubt, Malebranche proceeds to list all the ways in which the ideas of sensible objects could be presented to the mind:

•They come from the bodies that we perceive.

•The soul has the power of producing them in itself.

•They are produced by God, either in creating us or from time to time as there is use for them.

•The soul has in itself potentially all the perfections that it perceives in bodies;

•The soul is united with a being who has all perfection, and who has in himself the ideas of all created things.

He takes this to be a complete list of all the possible ways for the ideas of external objects to be presented to our minds. He devotes a whole chapter to each, rejecting the first four, and giving various arguments in support of the fifth: God is always present to our minds in a more intimate way than anything else is, so he can on the occasion of the impressions made on our bodies reveal to us, as far as he thinks proper and according to fixed laws, his own ideas of the object; and thus we see all things in God or in the divine ideas. [‘Occasion’, as used here and in several later passages, is a technical term in Cartesian philosophy. Physical events of kind K_1 can’t cause mental events of kind K_2, Malebranche held; but there seems to be such causation because God establishes regularities—‘laws’—according to which whenever a K_1 event occurs a K_2 event follows, the former being not the cause but the ‘occasion’ for the latter.]

At first glance this system may appear visionary; but when we consider that Malebranche agreed with the whole tribe of philosophers in taking ideas to be the immediate objects of perception, and that he found insuperable difficulties and even absurdities in every other hypothesis about ideas, it won’t be so surprising that a man of very great intellectual power should opt for this hypothesis; and, devout as he was, it probably pleased him all the more because it highlights our dependence on God and his continual presence with us. Malebranche distinguished more accurately than any previous philosopher •the objects that we perceive from •the sensations in our own minds which, by the laws of Nature, always accompany our perception of the object. In this as in many things he has great merit, for I think that this is a key that opens the way to a correct understanding both of our external senses and of other powers of the mind. Ordinary folk confuse •sensation with •other powers of the mind, and confuse it with •the objects ·they perceive·, because the purposes of everyday living don’t make a distinction necessary. Running these together in ordinary language has led philosophers in one period to treat things that are really sensations in our own minds as though they were external, and in another period—going of course! to the opposite extreme—taking almost everything to be a sensation or feeling in our minds.

Obviously Malebranche’s system doesn’t allow anything that we perceive by our senses to count as evidence of the existence of a material world; for God’s ideas, which are the objects we immediately perceive, were the same before the world was created as they are now. Malebranche was too sharp not to spot this consequence of his system, and too fair-minded not to acknowledge it. He fairly admits it, and tries to turn it to his advantage by making the authority of revelation the only evidence we have of the existence of matter. He shows that Descartes’s arguments to prove the existence of a material world, though as good as any that reason could provide, are not perfectly conclusive; and though he agrees with Descartes that we feel ourself strongly drawn to believing in the existence of a material world, he thinks that this isn’t sufficient, and that to succumb to such urges in the absence of evidence is to expose ourselves to perpetual delusion. He thinks, therefore, that the only convincing evidence we have of the existence of a material world is that revelation assures us that God created the heavens and the earth. . . . He is aware that this strange opinion may expose him to ridicule from those who are guided by prejudice, but for the sake of truth he is willing to bear it. But no author—not even Berkeley—has shown more clearly that neither his own system nor what philosophers commonly say about ideas leaves us with any evidence, whether from reason or from our senses, of the existence of a material world. It is only fair to Father Malebranche to acknowledge that Berkeley’s arguments are to be found, in full force, in his works.

[Reid then briefly discusses the views of John Norris, an English follower of Malebranche, who ‘has made a feeble effort’ to ‘prove that material things cannot be an immediate object of perception’. Then:]

Malebranche’s system was adopted by many devout people in France. . . .but it seems to have had no great currency in other countries. Locke wrote, but did not publish, a small tract against it. . . . But there is less strength and solidity in that than in most of his writings—he wrote it either •in haste or •at an advanced age when his intellect had lost some of its energy. Malebranche’s most formidable antagonist was his fellow-countryman, Antoine Arnauld, teacher at the Sorbonne and one of the sharpest writers the Jansenists have to boast of (though that sect has produced many). Malebranche was a Jesuit, and the bad feelings between the Jesuits and Jansenists gave him no reason to expect mercy from his learned antagonist! If you want to see Malebranche’s system attacked and defended, with each side displaying subtlety of argument and elegance of expression,. . . .you should read

Malebranche’s Search after Truth,

Arnauld’s True and False Ideas,

Malebranche’s Response to Arnauld’s Book,

and some subsequent replies and defences. In controversies of this kind the attacker usually has the advantage,. . . .for it is easier to overturn all the theories of philosophers on this subject than to defend any one of them. Bayle has remarked, rightly, that in this controversy Arnauld’s arguments against Malebranche’s system were often unanswerable, but that they held equally against Arnauld’s own system; and his ingenious antagonist knew well how to use this defence.

Chapter 8: The ‘common theory’, and the views of the Aristotelians and of Descartes

What I call ‘the common theory’ [see here] holds that we perceive external objects only by certain images that are in our minds or in the sensorium, ·the part of the brain· to which the mind is immediately present. Philosophers down through the centuries have differed both in •the names they have given to those images and in •their notions of what the images are. To list all their variations probably wouldn’t be worth the labour. I shall merely sketch the principal differences with regard to •their names and •their nature.

·NAMES·

Aristotle and his followers called the images presented to our •senses ‘sensible species’ or ‘forms’; those presented to our •memory or imagination were called ‘phantasms’; and those presented to our •intellect were called ‘intelligible species’; and they held that there can be no •perception or •imagination or •thought without species or phantasms. In later times, and especially since the time of Descartes, the items to which the ancient philosophers gave three different names came to be lumped together under the common name ‘ideas’. The Cartesians divided our ideas into three classes—ideas of •sensation, of •imagination, and of •pure thought. They held that the images of the objects of sensation and of imagination are in the brain, while the images of objects that are incorporeal are in the understanding or pure intellect.

Locke took ‘idea’ in the same sense as Descartes had done before him, to signify ‘whatever is meant by “phantasm”, “notion” or “species”’. He divided ideas into those of •sensation and those of •reflection; meaning by •the first the ideas of all corporeal objects, whether perceived, remembered, or imagined; by •the second the ideas of the powers and operations of our minds. What Locke calls ‘ideas’ Hume divides into two distinct kinds—‘impressions’ and ‘ideas’. The difference between these, he says, consists in the degrees of force and liveliness with which they strike on the mind. Under ‘impressions’ he brings all our sensations, passions and emotions as they make their first appearance in the soul. By ‘ideas’ he means the faint images of impressions, in thinking and reasoning.

Hartley gives the same meaning to ‘idea’ as Hume does, and what Hume calls ‘impressions’ he calls ‘sensations’, conceiving our •sensations to be occasioned by vibrations of the infinitesimal particles of the brain, and our •ideas by vibrations that are even smaller. . . .

·NATURE·

I shall now present in some detail, though briefly, the views of the Aristotelians and Cartesians (·in this chapter·) and of Locke, Berkeley and Hume (·in the next four chapters·) about what sort of thing these images are.

Aristotle seems to have thought that the soul consists of two parts, or rather that we have two souls:

(1) The animal soul, which Aristotle calls simply ‘the soul’. This is what is involved in •the senses, •memory, and •imagination. We have this in common with brute animals.

(2) The rational soul, which Aristotle calls ‘the intellect’. This is what is involved in •judgment, •opinion, •belief and •reasoning. Man has this, but the brute animals don’t.

He thought that the animal soul is a certain form of the body; it can’t be separated from the body, and it goes out of existence at death. . . . He defines a sense as that which can receive the sensible forms or species of objects without any of their matter—as soft wax receives the form of the seal without any of its matter. The forms of sound, of colour, of taste, and of other sensible qualities are all taken in by the senses in the same way.

Aristotle’s doctrine seems to imply that bodies are constantly sending out in all directions as many different kinds of forms-without-matter as they have different sensible qualities; for the forms of colour must enter by the eye, the forms of sound by the ear, and so on. I haven’t found Aristotle himself saying this explicitly, but his followers did. They argued over details, but the whole theoretical framework of these disputes. . . . is so far above my understanding that I might be unfair to it if I went into it in more detail.

Malebranche in his Search for the Truth devoted a whole chapter to arguing that material objects do not send out sensible species of their various sensible qualities.

The great revolution that Descartes produced in philosophy was the effect of •his greater genius aided by •the circumstances of the times. For more than a thousand years men had looked up to Aristotle as an oracle in philosophy. His authority was the test of truth. . . . Aristotelian doctrines were so closely interwoven with the whole system of scholastic theology that to •dissent from Aristotle was to •alarm the Church! ·Europe was dominated by Aristotle’s thought, and not even by the best of it·. The most useful and intelligible parts of Aristotle’s own writings were neglected, and philosophy became a set of techniques for speaking learnedly and disputing subtly without coming up with anything of use in human life. It bore a great crop of words but no works! It was splendidly designed for drawing a veil over human ignorance, and putting a stop to the progress of knowledge, by making men think that they knew everything. It also produced a big crop of controversies; but they were mostly about •words, or •things that don’t matter, or •things above the reach of the human faculties. The outcome of each controversy was what you might expect: the disputing parties fought without gaining or losing an inch of ground, until they were weary of the dispute or their attention was drawn away to some other subject.

Such was the philosophy of the schools [= ‘the Aristotle-dominated Roman Catholic philosophy departments’] of Europe during the centuries of darkness and barbarism that followed the decline of the Roman empire; so that philosophy needed to be reformed as much as religion did. The light began to dawn at last; a spirit of enquiry sprang up, and men got the courage to question Aristotle’s dogmas as well as the Popes’ decrees. The most important step in the reformation of •religion was to destroy the claim of ·Papal· infallibility, which had blocked men from using their own judgment in matters of religion. And the most important step in the reformation of •philosophy was to destroy the authority that Aristotle had had for so long without being challenged. The reform of philosophy had been attempted by Bacon and others, just as zealously as the reform of religion has been attempted by Luther and Calvin.

Descartes knew well the defects of the prevailing system, which had begun to lose its authority. His genius enabled him, and his spirit prompted him, to attempt a new one. He had worked hard at the mathematical sciences and had made considerable improvements in them. He wanted to introduce into other branches of philosophy the clarity and evidentness that he found in mathematics. [Descartes died about 135 years before this work appeared.]

Being aware of how apt we are to be led astray by prejudices that have been taught to us, Descartes thought that the only way to avoid error was to set oneself to doubt everything—to regard everything as uncertain, even things he had been taught to regard as most certain—until he encountered something that was so clearly and powerfully evident to him that it compelled his assent.

In this state of universal doubt, what first appeared to him to be clear and certain was his own existence. He was certain because he was conscious that he thought, that he reasoned, and that he doubted. So his argument to prove his own existence was this: cogito ergo sum [= ‘I think, therefore I exist’]. He took this to be the first of all truths—the foundation-stone on which the whole structure of human knowledge is built. . . . He was bowled over by the discovery of one certain principle that released him from the state of universal doubt, and he thought that this principle alone would serve as a foundation on which he could build the whole system of science. So he seems not to have taken much trouble to look for other first principles whose clarity and evidentness entitled them to be accepted by every man of sound judgment. The love of simplicity, which is so natural to the mind of man, led Descartes to apply the whole force of his mind to building the edifice of knowledge on this one principle, rather than looking for a broader foundation.

So he doesn’t count the evidence of the senses as a first principle, as he does the evidence of consciousness. He brought out the arguments of the ancient sceptics—that •our senses often deceive us. . . .and that •in sleep we often seem to see and hear things that we are convinced have never existed. But what chiefly led Descartes to think that he oughtn’t to trust his senses without proof of their truthfulness was that he took it for granted, as all philosophers had done before him, that •what he perceived were not external objects themselves but only certain images of them in his own mind, images called ‘ideas’. Consciousness made him certain that he had the ideas of sun and moon, earth and sea; but how could he be assured that there really existed external objects similar to these ideas?

Having reached the stage of being uncertain of everything but the existence of himself and of the operations and ideas of his own mind,. . . . Descartes didn’t stop there. Rather, he tried to prove by a new argument—drawn from his idea of a god—the existence of an infinitely perfect being who created him and all his faculties. Because this being is perfect (Descartes reasoned), he couldn’t be a deceiver; from which he inferred that his senses and the other faculties he found in himself are not deceptive but can be trusted when they are used properly.

Descartes sets out his system very clearly and sharply in his writings, which you should consult if you want to understand it.

Descartes’s merit is hard to grasp for anyone who doesn’t have any notion of the Aristotelian system in which he was educated. To throw off the prejudices of education, and to create a system of Nature totally different from the one had dominated the understanding of mankind for so many centuries, required an uncommon force of mind.

·WHAT DESCARTES WAS BROUGHT UP IN·

The world that Descartes presents to us is not only •structurally very different from that of the Aristotelians, but is—so to speak—•composed of different materials.

In the old system a kind of metaphysical sublimation turned everything into principles so mysterious that it’s an open question whether they were words without meaning or were notions too refined for human understanding. [Reid is probably using ‘sublimation’ in two of its senses at once: •intellectually making something higher or purer or more sublime, and •physically turning a solid into a gas!]

All that we observe in Nature, according to Aristotle, is a constant sequence of the operations of generation and corruption [= ‘coming into existence and going out of existence’, thought of mainly in biological terms]. The sources of generation are •matter and •form. All natural things are produced or generated by the union of matter and form, as though matter were the mother and form the father. As to matter—or ‘prime matter’ as it is called—it is neither substance nor accident; it has no qualities or properties; it is nothing •actually, but is everything •potentially. It has such a strong appetite for form that no sooner does it lose one form than it is clothed in another, and it is capable of having all forms one at a time. It has no nature of its own, but only the capacity for having any nature. This is the Aristotelian account of prime matter. ·This is not matter considered as stuff you can hold in your hand, that has a shape and size and weight and so on. That is secondary matter. Aristotle’s prime or first matter is just what is left of a substance if you subtract its form, i.e. subtract all its properties or qualities. That is why it has no nature of its own, why it is potentially anything but actually nothing, and so on·.

The other source of generation is form, act, perfection— in Aristotle’s system those three words signify the same thing. But we mustn’t think of form as consisting in the shape, size, arrangement, or movement of the parts of matter. These are indeed •accidental forms by which •artificial things are formed; but everything produced by •Nature has a •substantial form, which when joined to matter makes the thing to be what it is. The substantial form is a kind of informing soul that gives the thing its specific nature, and all its qualities, powers, and activity. Thus the substantial form of a heavy body is what makes it fall, the substantial form of a light body is what makes it rise. The substantial form of gold is what makes it ductile, fusible, heavy, yellow, and so on; and the same line of thought applies to every natural production. A change in the •accidental form of a body—·for example, a lump of gold being turned into a coin·—is merely an •alteration. But a change in a thing’s •substantial form—·for example, a lump of gold turning into lead·—is •generation and •corruption. It is corruption with respect to the substantial form (·gold·) of which the body is deprived, and generation with respect to the substantial form (·lead·) that takes its place. When a horse dies and turns to dust, the ·Aristotelian· philosophical account of the phenomenon is this: A certain portion of prime matter that was joined to the substantial form of a horse is deprived of that form and in the same instant is clothed in the substantial form of earth. As every substance must have a substantial form, some of the forms are •inanimate, some •vegetative, some •animal, and some •rational. The first three kinds can only exist in matter; but the last, according to the schoolmen, is immediately created by God and infused into the body, making one substance with it while they are united; yet capable of being separated from the body and existing by itself.

One last point: I said that the sources of generation are matter and form. I now add that the source of corruption is privation—·as when the gold (or the horse) is deprived of its substantial form·.

Those are the principles of natural things in the Aristotelian system. [Reid then briefly discusses how much or little this system has in common with the system of Pythagoras and of Plato, ending with:] But these two systems differed less from one another than Descartes’s differed from both.

·WHAT DESCARTES REPLACED IT BY·

In the world of Descartes we meet with only two kinds of beings, namely •body and •mind; •one the object of our senses, •the other the object of consciousness; both of them things of which we have a firm grasp if the human mind is capable of firmly grasping anything. The only qualities ascribed to body are •extension, shape, and motion; the only qualities ascribed to mind are •thought and its various modifications—·various thought-episodes, various ways of thinking·—of which we are conscious. He couldn’t see any common attribute, any resembling feature in the attributes of body and mind, so he concluded that they are distinct substances and totally different in kind. He held that body is by its very nature inanimate and inert, incapable of any kind of thought or sensation and unable to produce any change or alteration in itself.

To Descartes goes the honour of being the first person to draw a clear line between the •material and •intellectual worlds, which the old systems blended together so that it was impossible to say where the one ends and the other begins. It would be hard to express how much this distinction has contributed to modern improvements in the philosophy of body and the philosophy of mind.

One obvious consequence of it was ·the realization· that the only way to make any progress in the knowledge of minds is by careful reflection on the operations of our own mind. Malebranche, Locke, Berkeley, and Hume learned this lesson from Descartes; and we owe to it the most valuable discoveries that those philosophers made in this branch of philosophy. There is another way of reaching conclusions about the mind, namely by analogical thinking in which the •powers of the mind are described in terms of the •properties of body. This analogical approach

is something that most people find natural,

agreed with the principles of the old philosophy,

was the source of almost all the errors on this subject, and

was flatly contrary to the principles of Descartes.

So we can truly say that Descartes laid the foundation for the philosophy of the mind, and set us on the path that all wise men now agree is the only one on which we can expect success.

·AN ASIDE ON THE BREAKTHROUGH IN PHYSICS·

With regard to physics, or the philosophy of body, even though Descartes didn’t lead men onto the right path we must give him credit for bringing them out of a wrong one. When the Aristotelians assigned to every species of body a particular substantial form that produces in an unknown manner all the effects we observe in it, they put a stop to all improvement in physics. Heaviness and lightness, fluidity and hardness, heat and cold—these were qualities arising from the substantial form of the bodies that had them. The Aristotelians always had ready at hand ·the concepts of·

generation and corruption,

substantial forms, and

occult [= ‘hidden’] qualities

to ‘explain’ any phenomenon. Thus this philosophy, instead of ·genuinely· accounting for any of the phenomena of Nature, merely managed to give learned names to their unknown causes, and fed men with the husks of barbarous terminology instead of the fruit of real knowledge.

Through the spread of the Cartesian system, ‘prime matter’ and ‘substantial forms’ and ‘occult qualities’—along with all the jargon of Aristotelian physics—fell into utter disgrace and were never mentioned by the followers of the new ·Cartesian· system except as something to be ridiculed. Men became aware that their understanding had been hoodwinked by those hard terms. They were now accustomed to explaining the phenomena of Nature in terms that are perfectly comfortable for human understanding—shape, size, and motion of particles of matter—and they could no longer put up with anything in philosophy that was obscure and unintelligible. After a reign of more than a thousand years, arrayed in the mock majesty of his ‘substantial forms’ and ‘occult qualities’, Aristotle was now exposed as an object of derision, even to the man in the street. . . .

Given the weakness of human nature, men can’t be expected to rush violently from one extreme without going more or less to the opposite extreme! Descartes and his followers were not free of this weakness: they thought that •extension, •shape and •motion were all that was needed to explain all the phenomena of the material system. To allow into their system any other qualities, with unknown causes, would be to return to Egypt, from which they had been so happily delivered. [Reid is referring to the Old Testament story about Moses leading the Israelites out of bondage in Egypt.]

When Newton’s doctrine of gravitation was published, the great objection to it—which stopped it from being generally accepted in Europe for half a century—was that gravitation seemed to be an occult quality because it couldn’t be accounted for by extension, shape, and motion, the known attributes of body. His defenders found it hard to answer this objection to the satisfaction of those who had been initiated in the principles of the Cartesian system. But men gradually came to realize that in revolting against Aristotle the Cartesians had gone to the opposite extreme; experience convinced them that there are qualities in the material world whose existence is certain though their cause is occult ·or hidden·. Admitting this is behaving in a way that is utterly appropriate for a philosopher, honestly confessing human ignorance.

Just as our whole knowledge of the mind must come from carefully observing what happens within ourselves, so our whole knowledge of the material system must come from what we can learn through our senses. Descartes knew this, and his system wasn’t as unfriendly to observation and experiment as the old ·Aristotelian· system was. He conducted many experiments, and earnestly called on all lovers of truth to help him in this work. But ·two of his beliefs made him unduly optimistic about how much could be learned from just a few experiments·. He believed that

•all the phenomena of the material world result from extension, shape, and motion,

and that

•God always combines these so as to produce the phenomena in the simplest way possible.

•God always combines these so as to produce the phenomena in the simplest way possible. ·Having taken these two doctrines on board·, he thought that from a few experiments he might be able to discover the simplest way in which the obvious phenomena of Nature could be produced purely by extension, shape and motion, and that this ·simplest possible way· must be the way in which the phenomena actually are produced. Given his basic principles, his conjectures were ingenious; but they have turned out to be far from the truth—so far that they ought to discourage philosophers from ever trusting to conjecture regarding the operations of Nature. . . .

It was left for Newton to point out clearly the road to the knowledge of Nature’s works. Taught by Bacon to despise hypotheses, as the fictions of the human imagination, Newton laid it down as a rule of philosophising that nothing should be assigned as the cause of a natural thing unless it can be proved that it really exists. He saw that the furthest men can go in accounting for phenomena is discovering the laws of Nature according to which they are produced; so that the true method of philosophising is this:

From real facts, ascertained by observation and experiment, establish by sound induction what the laws of Nature are, and use the laws discovered in this way to account for the phenomena of Nature.

Thus the natural philosopher has the rules of his art fixed just as precisely as does the mathematician, and can be just as sure when he keeps to them and when he doesn’t. A law discovered through induction is not demonstratively evident, but it has the kind of evidentness on which all the most important affairs of human life must rest.

Pursuing this road without deviation, Newton discovered the laws of our planetary system and of the rays of light, and gave the first and most important examples of the sound kind of induction that Bacon ·advocated, but· could only delineate in theory ·because in his day there weren’t any examples of it·.

How strange is it that the human mind should have wandered for so many ages without stumbling onto this path? How much stranger that after the path has been clearly discovered and good progress made along it, many choose instead to wander in the fairyland regions of hypothesis?

·RETURNING TO THE TOPIC OF PERCEPTION·

Let us return to Descartes’s views about how we perceive external objects. (I digressed from it because I wanted to do justice to the merit of that great reformer in philosophy.) He took it for granted, as the old philosophers had done, that what we immediately perceive must be either •in the mind itself or •in the brain to which the mind is immediately present. According to Descartes’s philosophy, the impressions made on our sense-organs, nerves, and brain can’t be anything but various special cases of extension, shape, and motion. There can’t be anything in the brain that is like sound or colour, taste or smell, heat or cold; these are sensations in the mind which, by the laws of the union of soul and body, are stirred up when certain traces occur in the brain. Descartes calls those brain-traces ‘ideas’, but he doesn’t think that they have to be perfectly like the things they represent any more than words or signs resemble the things they signify. But he says that we may allow a slight resemblance, so as to follow generally accepted views as far as we can. Thus, we know that a picture in a book can represent houses, temples and groves, yet it doesn’t have to be perfectly like what it represents—quite the contrary, indeed, for a circle must often be represented by an ellipse, a square by a rhombus, and so on.

Sense-perceptions, Descartes thought, relate purely to the union of soul and body. They usually reveal to us only things that might hurt or profit our bodies; and only rarely and through some fluke do they exhibit things as they are in themselves. By keeping this in mind we can learn to throw off the prejudices of the •senses, and attend with our •intellect to the ideas that Nature has implanted in it. This will lead us to understand that the nature of matter doesn’t consist •in the things that affect our senses—such as colour, or smell or taste—but only •in its being something extended in length, breadth, and depth.

Descartes’s writings are in general remarkably clear; and he undoubtedly intended that in this respect his philosophy should be a perfect contrast to Aristotle’s; yet in different parts of his writings his treatment of our perception of external objects is sometimes obscure and even inconsistent. Did he have different opinions on sense-perception at different times. or was it just that he was struggling with difficulties? I won’t offer to answer this.

On two points in particular I can’t reconcile Descartes to himself: (1) regarding the place of the ideas or images of external objects that are the immediate objects of perception; and (2) regarding the truthfulness of our external senses.

(1) He sometimes locates the ideas of material objects in the brain, not only when they are perceived but also when they are remembered or imagined; and this has always been taken to be the Cartesian doctrine. But he sometimes warns us not to think of the images or traces in the brain as being perceived, as if there were eyes in the brain; these traces are only occasions on which, by the laws of the union of soul and body, ideas are aroused in the mind; and therefore there is no need for the traces to resemble exactly the things they represent, any more than for words or signs to resemble exactly the things they signify. [For ‘occasion’ see the note here.]

I don’t think that these two opinions can be reconciled. For if the images or traces in the brain are perceived, they must be the •objects of perception and not merely the •occasions for it. Putting it the other way around: if they are only the occasions for our perceiving, they aren’t themselves perceived at all. Descartes seems to have hesitated between the two opinions, or to have alternated between them. . . .

Newton and Clarke uniformly speak of the species or images of material things as being in the part of the brain called the sensorium, and as perceived by the mind that is present there; though Newton speaks of this point only incidentally, and with his usual modesty in the form of a question. Malebranche is perfectly clear and unambiguous in this matter. According to his system, the images or traces in the brain are not perceived at all—they are only occasions on which, by the laws of Nature, certain sensations are felt by us and certain of god’s ideas are revealed to our minds.

(2) Descartes seems to waver also regarding the trust that we should put in the testimony of our senses.

Sometimes he infers from •God’s being perfect and not a deceiver that •our senses and our other faculties can’t be untruthful. And since we seem clearly to perceive that the idea of matter comes to us from external things that it perfectly resembles, therefore we must conclude that there really exists something that is extended in three dimensions and has all the properties that we clearly perceive to belong to an extended thing.

At other times we find Descartes and his followers making frequent complaints, as all the ancient philosophers did, about the untrustworthiness of the senses. He warns us to throw off the prejudices of sense, and attend only with our intellect to the ideas implanted there. This will enable us to perceive that the nature of matter doesn’t consist in hardness, colour, weight, or any of the things that affect our senses, but only in being extended in three dimensions. The senses, Descartes says, are only relative to our present state; they exhibit things only as they tend to profit or to hurt us and only rarely and accidentally as they are in themselves.

What led Descartes to deny that there is any •substance of matter distinct from the •qualities of matter that we perceive was probably his unwillingness to admit into philosophy anything of which we don’t have a clear and distinct conception. We say that matter is

something that is extended, shaped, and movable.

So extension, shape, and mobility are not •matter but qualities belonging to this •‘something’ that we call matter. Descartes had no taste for this obscure ‘something’ that is supposed to be the subject or substratum of those qualities; so he therefore maintained that extension is the very essence of matter. But as we have to credit space as well as matter with being extended, he was forced to maintain that space and matter are the same thing, differing only in how we conceive them; so that wherever there is space, there is matter—and no void, no empty space, left in the universe. . . .

It was probably for the same reason that Descartes maintained that the essence of the soul consists in thought. He wouldn’t allow it to be an unknown ‘something’ that has the power of thinking; so it can’t exist without thought ·because it is thought·. And because he believed that all thought must involve ideas, ·Descartes concluded that· the soul must have had ideas when it was first formed—ideas that must therefore be innate.

Those who came after Descartes had various views concerning the nature of body and mind. Many have maintained that a •body is only a collection of qualities to which we give one name, and that the notion of a subject. . . .to which those qualities belong is a mere fiction of the mind. Some have even maintained that a •soul is only a sequence of related ideas, without any subject to which those ideas belong. You can see from what I have said how far these notions are allied to the Cartesian system.

The triumph of the Cartesian system over that of Aristotle is one of the most remarkable revolutions in the history of philosophy, and has led me to dwell on it for longer than the present subject perhaps required. . . .

·Once Descartes’s system took hold·, the authority of Aristotle was extinguished. The •reverence for difficult words and dark notions by which men’s understanding had been strangled in past centuries was turned into •contempt, and anything that wasn’t clearly and distinctly understood was regarded as suspect. This is the spirit of the Cartesian philosophy, which is a more important gift to mankind than any particular Cartesian doctrines; and for exercising this spirit so zealously and spreading it so successfully Descartes deserves immortal honour.

Note, though, that Descartes rejected only one part of the ancient theory about the sensory perception of external objects, and that he adopted the other part. The ancient theory can be divided into two parts:

(1) Images, species, or forms of external objects come from the object and reach the mind through the senses.

(2) What is actually perceived is not the external object itself but only the species or image of it in the mind.

Descartes and his followers rejected (1), refuting it by solid arguments. But neither he nor his followers thought of calling (2) into question, for they were convinced that what we perceive is only a representative mental image of the external object, not the object itself. And this image, which the Aristotelians called a ‘species’, he called an ‘idea’—a mere change of •name, presenting no challenge to the •thing.

Descartes took great pains to throw off the prejudices that he had been taught, to dismiss all his former opinions, and to assent only to things that were so evident that they compelled his assent; which makes it strange that he wasn’t led to doubt this doctrine of the ancient philosophy. It’s obviously a philosophical opinion, for the vulgar undoubtedly think that we immediately perceive the external object, not a mere representative image of it. That’s why they look on it as total lunacy to call in question the existence of external objects.

It seems to be accepted as a basic principle by the learned and the uneducated alike that •what is really perceived must exist, i.e. that to perceive what doesn’t exist is impossible. So far the uneducated man and the philosopher agree. The uneducated man says:

I perceive the external object, and I perceive it to exist. Nothing could be more absurd than to doubt that it exists.

The Aristotelian says:

What I perceive is the individual form of the object, which came immediately from the object and makes an impression on my mind as a seal does on wax; and therefore I can have no doubt of the existence of an object whose form I perceive.

But what does the Cartesian say? Well, for a start:

I don’t perceive the external object itself.

So far he agrees with the Aristotelian and differs from the uneducated man. He continues:

But I perceive an image or form or idea in my own mind or in my brain. I am certain of the existence of the idea because I immediately perceive it. But how this idea is formed, or what it represents, is not self-evident; so I must find arguments that will let me infer from •the existence of the idea that I perceive •the existence of an external object that it represents.

Given that these are the principles of the •uneducated man, of the •Aristotelian, and of •the Cartesian, I think that they all reason correctly, each from his own principles: the Cartesian has strong grounds to doubt of the existence of external objects; the Aristotelian very little ground for doubt; and the uneducated man has none at all. Why the difference? Well, the uneducated man has no hypothesis; the Aristotelian leans on a hypothesis; and the Cartesian leans on half of it.

Descartes, according to the spirit of his own philosophy, ought to have called in question both parts of the Aristotelian hypothesis, or to have given his reasons for adopting one part along with reasons for rejecting the other part. ·The views of the man in the street ought to have put him onto this·. Uneducated people, who can do just as good a job of perceiving objects by their senses as philosophers can, and should therefore know as well as philosophers do what it is that they perceive, have been unanimous in holding that what they perceive are not ideas in their own minds but external things. It might have been expected that a philosopher who was so cautious as not to take his own existence for granted without proof wouldn’t have taken it for granted without proof that everything he perceived was only ideas in his own mind!

But if Descartes took a rash step here (as I think he did), he oughtn’t to bear the blame alone. His successors have still followed that same track, and following his example have adopted one part of the ancient theory—namely that the objects we immediately perceive are only ideas. All their systems are built on this foundation.

Chapter 9: Locke’s views

The reputation that Locke’s Essay concerning Human Understanding had in England from the beginning, and that it has gradually acquired abroad, is a sufficient testimony of its merit. [Locke died about 80 years before this work appeared.] There may be no metaphysical book that has been so generally read by those who understand English, or that is better fitted to •teach men to think with precision and •to inspire in them the honesty and love of truth that is the genuine spirit of philosophy. I think this was the first example in the English language of such remarkably simple and clear writing on such abstract subjects, and I’m glad to say that in this Locke has been imitated by others who came after him. No author has more successfully pointed out the danger of ambiguous words, and the importance of having clear and settled notions in judging and reasoning. His points about

the various powers of the human understanding,

the use and misuse of words, and

the extent and limits of human knowledge

are drawn from attentive reflection on the operations of his own mind, the true source of all real knowledge on these subjects; and they show an unusual degree of penetration and judgment. But Locke doesn’t need praise from me; and I make these remarks only so that when I have occasion to differ from him you won’t think I am unaware of the merit of an author whom I highly respect—one whose writings first led me into philosophy and then kept me working at it.

He sets out in his Essay with a full conviction, shared with other philosophers, that ideas in the mind are the objects of all our thoughts in every operation of the understanding. This leads him to use the word ‘idea’ so much more often than was usual in the English language that he felt a need to apologise for it:

‘Idea’ seems to be the best word to stand for whatever is the object of the understanding when a man thinks; I have used it to express whatever is meant by ‘phantasm’, ‘notion’, ‘species’, or whatever it is that the mind can be employed about in thinking; and I couldn’t avoid frequently using it. Nobody, I presume, will deny that there are such ideas in men’s minds; everyone is conscious of them in himself, and men’s words and actions will satisfy him that they are in others. (Essay I.i.8)

Speaking of the reality of our knowledge, he says:

Obviously the mind knows things not •immediately but only •through the intervention of its ideas of them. So our knowledge is real only to the extent that our ideas conform to the reality of things. But what is to be the criterion for this? How can the mind, which perceives nothing but its own ideas, know that they agree with things themselves? This seems like a hard thing to discover; but I think there are two sorts of ideas that we can be sure do agree with things. (IV.iv.3)

We see that Locke was as aware as Descartes was that the doctrine of ideas made it both •necessary and •difficult to prove the existence of a material world external to us; because according to that doctrine the mind perceives in itself nothing but a world of ideas. Not only Descartes, but also Malebranche, Arnauld, and Norris had seen this difficulty and tried without much success to overcome it. Locke attempts the same thing, but his arguments are feeble. He even seems to be aware of this, for he concludes his reasoning with this remark: ‘Such an assurance of the existence of things outside us is sufficient to direct us in the attaining the good and avoiding the evil that is caused by them; and this is what really matters to us in our acquaintance with them.’ (IV.xi.8)Anyone who denies the existence of a material world can accept this!

[Then three paragraphs about differences between Locke and Descartes on topics not directly relevant to senseperception. Reid’s report on Locke’s distinction between ‘real essences’ and ‘nominal essences’ is notably approving. Then:]

Since the time of Descartes, philosophers have differed greatly with regard to •what part they think the mind plays in the construction of the representative beings called ‘ideas’ and with regard to •how this work is carried on.

[Two paragraphs sketching Robert Hook’s view that ideas are material substances. Then:]

Locke hasn’t gone into such fine detail about how ideas are manufactured; but he ascribes to the mind a very considerable part in forming its own ideas. With regard to our sensations, the mind is passive, ‘they being produced in us only by different speeds and kinds of motion in our animal spirits as they are variously stirred up by external objects’ (II.viii.4). These, however, go out of existence as soon as they stop being perceived; but through memory and imagination ‘the mind is able to revive them again when it wants to, and as it were to paint them on itself again, with varying degrees of difficulty’. (II.x.2)

As for the ideas of reflection, the only cause he assigns to those is the attention that the mind can give to its own operations. So these are formed by the mind itself. He also ascribes to the mind the power •of compounding its simple ideas into complex ones of various sorts, •of repeating them and adding the repetitions together; •of dividing and classifying them; •of contemplating them two at a time and on that basis forming the ideas of the relations between them; even •of forming a general idea of a species or genus by taking from the idea of an individual everything that distinguishes it from other individuals of that kind, till at last it becomes an abstract general idea that is common to all the individuals of the kind.

I think these are ·all· the powers that Locke ascribes to the mind itself in the manufacture of its ideas. Berkeley, as we shall see later, abridged them considerably, and Hume even more.

Our ideas of the various qualities of bodies are not all of the same kind, Locke thinks. Some are images or resemblances of what is really in the body, others are not. There are certain qualities inseparable from matter—such as extension, solidity, shape, mobility—and our ideas of these are real resemblances of the qualities in the body, which Locke calls ‘primary qualities’. He labels as ‘secondary qualities’ colour, sound, taste, smell, heat, and cold, which he thinks are only bodies’ powers to produce certain sensations in us; and these sensations don’t resemble anything else, though they are commonly thought to be exact resemblances of something in the body. . . .

Although no author has more merit than Locke in pointing out the ambiguity of words, and by that means solving many knotty problems that had tortured the brains of the schoolmen, I think that he has sometimes been misled by the ambiguity of the word ‘idea’, which he uses so often on almost every page of the Essay. [The Essay contains nearly 3800 occurrences of the word ‘idea’.]

When I explained this word I called attention to two meanings that are given to it, a popular meaning and a philosophical one. In the popular meaning, to ‘have an idea’ of something is simply to think of it. ·Don’t be misled by the occurrence of the noun ‘idea’ in these locutions·.

Although the operations of the mind are most properly and naturally—and indeed, in popular speech, most commonly—expressed by active verbs, there is another way of expressing them that is less common but equally well understood.

To think of a thing = to have a thought of it

To believe a thing = to have a belief in it

To see a thing = to have a sight of it

To conceive a thing = to have a conception, notion, or idea of it

—the members of each of these pairs are perfectly synonymous. In these phrases, ‘thought’ means nothing but the act of thinking, ‘belief’ means the act of believing, and ‘conception’ or ‘notion’ or ‘idea’ means the act of conceiving; ·so those nouns shouldn’t be thought of a standing for particular mental things·. To ‘have a clear and distinct idea’ is in this sense simply to conceive the thing clearly and distinctly. When the word ‘idea’ is taken in this popular sense, it is beyond question that we have ideas in our minds. To think without ideas would be to think without thought, which is an obvious contradiction.

But the word ‘idea’ also has another meaning, used only by philosophers and based on a philosophical theory that never occurs to the man in the street. Philosophers ancient and modern have maintained that the mind’s operations. . . .can only be employed on objects that are present in the mind, or in the brain where the mind is supposed to be located. Therefore objects that are distant in time or place—·these being the two ways of not being present·—must have a representative in the mind or in the brain, some image or picture of them which is what the mind actually contemplates. . . . As this has been a common opinion among philosophers as far back as we can trace philosophy, it isn’t surprising that they should be apt to confuse •the operation of the mind in thinking with •the idea or object of thought that is supposed to be accompany any act of thinking—·i.e. to confuse •‘idea’ in its vulgar sense with •‘idea’ in its philosophical sense·.

If we have any respect for the common sense of mankind, •thought and •the object of thought are different things and ought to be distinguished. It’s true that thought has to have an object, for anyone who thinks must think of something; but •the object he thinks of is one thing, and •his thought of it is something else. They are distinguished in all languages, even by the vulgar; and many things can be said about thought—i.e. about the operation of the mind in thinking—which it would be wrong and even absurd to say about the object of that operation.

From this I think it is evident that if ‘idea’ in a work where it occurs in every paragraph is used without any mention of its ambiguity—sometimes signifying thought or the operation of the mind in thinking, sometimes signifying the internal objects of thought that philosophers suppose—this must create confusion in the thoughts both of the author and of the readers. I take this to be the greatest blemish in Locke’s Essay.

[Then a page or so of detailed textual discussion, focussing on the fact that Locke seems to say that we can think only about ideas and that we can think about external objects, but evidently doesn’t think that those objects are ideas. Then:]

The necessary consequence of this seems to be that there are two objects of my thought about Alexander the Great— the •idea that is in my mind and the •person represented by that idea, the idea being the immediate object of my thought, while Alexander is also the object of the same thought, but not the immediate object. This is hard to swallow, for it means that every thought of external things has a double object. Everyone is conscious of his own thoughts, but no-one perceives any such doubleness in the object he thinks about, even when he looks in on himself most attentively. . . .

[Then a paragraph questioning whether it even makes sense to talk of ‘an object of thought that isn’t an immediate object of thought’. Then:]

So I think that if philosophers insist on maintaining that ideas in the mind are the only immediate objects of thought, they will be forced to grant that they are the only objects of thought, and that we can’t possibly think of anything else. Locke apparently didn’t see that this was the •consequence of maintaining that ideas in the mind are the only immediate objects of thought; for he surely did believe that we can think of many things other than ideas in the mind.

The •consequence was seen by Berkeley and Hume, however; and they chose to admit the conclusion rather than give up the principle from which it follows. . . .

In explaining the word ‘idea’, Locke says that he uses it for whatever is meant by ‘phantasm’, ‘notion’, ‘species’ (I.i.8). Here are three synonyms for the word ‘idea’. The first and third are excellent for expressing the philosophical meaning of the word. . . . But ‘notion’ is a word in common language, meaning exactly what ‘idea’ means in its popular meaning but not in its philosophical meaning.

When these two different meanings of ‘idea’ are run together in a considered and explicit explanation of the word, we can hardly expect them to be carefully distinguished in the frequent use of it. Many passages in the Essay are intelligible only when ‘idea’ is taken in one of those two senses, and in many other passages it has to be taken in the other sense. Probably Locke wasn’t attending to this ambiguity, and simply used the word in one sense or the other as the context required; and most of his readers have probably done the same.

Locke also quite often uses ‘idea’ in a third sense, in which it signifies objects of thought that are not in the mind but external. (He seems to be aware of this, and somewhere makes an apology for it.) In ever so many places he asserts that all human knowledge consists in the perception of the agreement or disagreement of our ideas. To make this mean something that is consistent with his principles, we have to take ‘ideas’ to signify every object of human thought, whether mediate or immediate—in short, everything that can be signified by the subject or predicate of a proposition.

Thus we see that ‘idea’ has three different meanings in the Essay; and the author seems to have used it sometimes in one meaning and sometimes in another, without being aware of any change in the meaning. The reader slides easily into the same mistake, with the meaning that gives the best sense to each context being the one that most readily comes to his mind. . . .

Locke is not alone in this fault of attending too little to the distinction between the •operations of the mind and the •objects of those operations. Although this distinction is familiar to the vulgar, and found in the structure of all languages, philosophers when they speak of ‘ideas’ often run the two together. They are led to do this by their theory about ideas: for ideas are supposed to be a shadowy kind of beings, intermediate between •the thought and •the object of thought, so they sometimes seem to coalesce with the thought, sometimes with the object of thought, and sometimes to have a separate existence of their own.

The same philosophical theory of ideas has led philosophers to run together the different operations of the understanding, calling them all ‘perceptions’. Locke did this sometimes, but not as often as some who came after him. The vulgar give the name ‘perception’ to the immediate knowledge of external objects which we have by our external senses. This is its proper meaning in our language, though sometimes it can be applied to other things metaphorically or analogically. When I think of something that doesn’t exist—such as the city of Atlantis—I don’t perceive it; I only conceive or imagine it. When I think of what happened to me yesterday I don’t perceive it; I remember it. When I am in pain from gout, it isn’t proper to say that I perceive the pain; I feel it, or am conscious of it. It is not an object of perception, but of sensation and of consciousness. Here we see the vulgar very properly distinguishing the different operations of the mind, and never giving the same name to things that are so different in their nature. But the theory of ideas leads philosophers •to think of all those operations as being of one kind, and •to give them one name. They are all, according to that theory, perceptions of ideas in the mind. Perceiving, remembering, imagining, being conscious—these are all perceiving ideas in the mind, and are called ‘perceptions’. . . .

It seems unlikely that philosophers who have carefully studied the operations of their own minds would describe them less properly and less clearly than the vulgar do—but although unlikely it really is the case. The only explanation for this strange phenomenon seems to be this:

The vulgar aren’t looking for a theory to account for the operations of their minds. They know that they see and hear and remember and imagine; and those who think clearly will express these operations clearly, as their consciousness represents them to the mind. But philosophers think they ought to know not only •that there are such operations but •how they are performed—how they see and hear and remember and imagine. And having invented a theory to explain these operations in terms of ideas or images in the mind, they make their terminology fit their theory; and in this way a false theory darkens the phenomena it is trying to explain.

I shall examine this theory later on. Here I merely remark that if it is false, it can be expected to lead able men who adopt it to confuse the operations of the mind with their objects, and to confuse different operations with one another, even where the common language of uneducated people clearly distinguishes them. Someone who trusts to a false guide is in greater danger of being led astray than someone who trusts his own eyes, even if he doesn’t know the road at all well.

Chapter 10: Berkeley’s views

George Berkeley published his New Theory of Vision in 1709, his Principles of Human Knowledge in 1710, and his Three Dialogues in 1713. . . . Everyone regards him as having great merit as an excellent writer, and a very acute and clear reasoner, on the most abstract subjects—not to speak of his very conspicuous personal virtues. [Berkeley died about 30 years before this work appeared.] Yet the doctrine that is mainly propounded in the works I have mentioned, and especially in the second and third of them, has generally been thought so very absurd that hardly anyone thinks he believed it himself or that he seriously meant to convince others of its truth.

He maintains that there is no such thing as matter; that sun and moon, earth and sea, our own bodies and those of our friends, are nothing but ideas in the minds of those who think of them, and don’t exist when they are not the objects of thought. All there is in the universe, Berkeley holds, falls into two categories, namely minds and ideas in the mind. He thinks he has demonstrated this, by a variety of arguments based on principles of philosophy that everyone accepts.

But however absurd this doctrine might appear to •uneducated people, who consider the existence of the objects of sense as the most evident of all truths and not open to question for anyone in his right mind, the •philosophers who had been accustomed to regarding ideas as the immediate objects of all thought were not entitled to take such a dim view of this doctrine of Berkeley’s.

They were taught by Descartes and by all who came after him that the existence of the objects of sense is not self-evident, and needs to be proved by arguments; and although Descartes and many others had worked to find such arguments, the ones they came up with seemed not to have the force and clarity that one might expect in such an important matter. •Norris had declared that all those arguments had made it merely probable, by no means certain, that there is an external world. •Malebranche thought that the existence of an external world rested on the authority of revelation, and that the reason-based arguments for it were not perfectly conclusive. •Others thought that the argument from revelation was fallacious, because revelation comes to us by our senses and must rest on their authority.

Thus we see that the new philosophy had been inching its way towards Berkeley’s position; and whatever others might say, the philosophers had no right to look on it as absurd or unworthy of a fair examination. Several authors tried to answer his arguments, but with little success; others admitted that they couldn’t answer the arguments or accept their conclusion. Berkeley probably made very few converts to his doctrine; but it is certain that he made some, and that he himself continued to the end of his life firmly convinced that his doctrine is true and is important for the growth of human knowledge and especially for the defence of religion. . . .

[Then a page and half in which Reid reports on Berkeley’s New Theory of Vision. This doesn’t assert the whole doctrine of the two later works, maintaining only that the objects of sight are merely ideas in the mind. Reid praises warmly its work on the perception of distance, and on Berkeley’s account of] how the objects of sense would be thought of by a thinking being who could see but couldn’t touch them. Shallow thinkers may see this as a trivial question; but Berkeley saw it differently, and so will anyone who can enter into it and who knows how important it is in explaining many of the phenomena of vision. [Twenty years earlier, Reid, following Berkeley’s lead, dug deeply into this topic in his Inquiry into the Human Mind, chapter 6, sections 8, 11.] Berkeley seems indeed to have exerted more force of genius in this than in the main part of his system, ·to which I now turn·.

In the new philosophy, the pillars by which the existence of a material world was supported were so feeble that it didn’t need the strength of a Samson to pull them down; and in this matter we have less reason to admire •the power of Berkeley’s thought than to admire •his boldness in publishing to the world an opinion that uneducated people would be apt to interpret as a sign of madness.

A man who was quite convinced of the doctrine of ideas universally accepted by philosophers, if he could only muster up the courage to call in question the existence of a material world, would easily find unanswerable arguments in that very doctrine. ‘Some truths are so close to the mind, and so obvious,’ he writes, ‘that as soon as you open your eyes you will see them. An important truth of that kind is this: All the choir of heaven and furniture of the earth, in a word all those bodies that compose the mighty structure of the world, have no existence outside a mind.’ (Principles 6)

The principle from which this important conclusion is clearly inferred is laid down in the first sentence of his Principles of Human Knowledge as evident; and indeed it has always been acknowledged by philosophers:

Anyone who surveys the objects of human knowledge will find it evident that they are all ideas that are either •imprinted on the senses or •perceived by attending to one’s own emotions and mental activities or •formed from ideas of the first two types with help from memory and imagination, by compounding or dividing or reproducing ideas of those other two kinds.

This is the foundation on which the whole system rests. If this is true, then indeed the existence of a material world must be a dream that has deceived all mankind from the beginning of the world.

The foundation on which such a structure rests needs to be very solid and well established, but all Berkeley says on its behalf is that it is ‘evident’. If he means that it is self -evident, that indeed might be a good reason for not offering any direct argument in support of it. But I don’t that this can rightly be said. A self-evident proposition is one that appears evident to every man of sound understanding who firmly grasps its meaning attends to it without prejudice. Can that be said of the proposition that all the objects of our knowledge are ideas in our own minds? To any man who hasn’t had instruction in philosophy, I believe, this proposition will appear very improbable if not absurd. However scanty his knowledge may be, he does think that the sun and moon, the earth and sea, are objects of it; and it won’t be easy to convince him that those objects of his knowledge are ideas in his own mind, and don’t exist when he doesn’t think of them! Speaking for myself: I used to believe this doctrine of ideas so firmly that I accepted the whole of Berkeley’s system in consequence of it; then I found it to have other consequences that worried me more than did the lack of a material world; and that prompted me to ask myself: ‘What evidence do I have for this doctrine that all the objects of my knowledge are ideas in my own mind?’ Ever since that time more than forty years ago, I have been for looking for evidence for this principle, and I think I have done this honestly and without bias. My search hasn’t turned up any support for the principle other than the authority of philosophers.

I shall examine the case for it later on. At present I shall only remark that all the arguments brought by Berkeley against the existence of a material world are based on it, and that he hasn’t tried to give any evidence for it, merely taking it for granted as other philosophers had done before him.

If the principle is true, Berkeley’s system is secure. No demonstration could be more evident than his reasoning from the principle. Whatever is perceived is an idea, and an idea can exist only in a mind. It doesn’t exist when it is not perceived; and the only thing that can be like an idea is another idea.

[Then two paragraphs reporting that Berkeley himself thought that, given the ‘principle’, very little argument was needed to establish his conclusion; and that most of his time and energy went into defensive moves, anticipating and meeting possible objections, and so on. Then:]

Berkeley foresaw the opposition that would be made to his system from two different quarters—first from the philosophers, and secondly from the vulgar, who are led by the plain dictates of Nature.

He had the courage to oppose the philosophers openly and explicitly; he was more afraid of the vulgar, and therefore takes a great deal of trouble—and, I think, uses some skill—to bring the vulgar over to his side. This is particularly observable in his Three Dialogues. . . . He writes openly that his views ‘carry with them a great opposition to the prejudices of philosophers’, ·but his attitude to the vulgar is different·. [In passages from the Dialogues, Hylas speaks for critics of Berkeley’s system, Philonous speaks for Berkeley.] When Hylas objects: ‘You can never persuade me, Philonous, that denying the existence of matter. . . .isn’t contradictory to the universal sense of mankind’, he answers:

I would like both our positions to be fairly stated and submitted to the judgment of men who have plain common sense without the prejudices of a learned education. Let me be represented as one who trusts his senses, who thinks he knows the things he sees and feels, and has no doubts about their existence. . . . If by ‘material substance’ is meant only sensible body, that which is seen and felt (and I dare say that unphilosophical people mean no more), then I am more certain of matter’s existence than you or any other philosopher claim to be. If there is anything that turns people in general off from the views that I support, it is the mistaken idea that I deny the reality of sensible things. But it is you who are guilty of that, not I, so what they are really hostile to are your notions, not mine.

·And a few pages earlier·:

I am content to appeal to the common sense of the world for the truth of my view.

·And a few pages further back still·:

I have the common man’s frame of mind; I am simple enough to believe my senses and to leave things as I find them.

[Then some further quotations providing yet more evidence for] Berkeley’s concern to reconcile his system to the plain dictates of Nature and common sense, while expressing no concern to reconcile it to the received doctrines of philosophers. . . . It’s a pity that he didn’t carry his suspicion of the doctrine of philosophers far enough to doubt the philosophical tenet on which his whole system is built, namely that the things immediately perceived by the senses are ideas existing only in the mind!

And yet it doesn’t seem easy to make the vulgar opinion come to terms with Berkeley’s system. To accomplish this he seems to me to pull the two towards one another, with some straining.

[Then several pages in which Reid sketches various of Berkeley’s moves aiming to reconcile his system with the common-sense opinions of the vulgar, and sums up thus: ‘I think that Berkeley has carried this attempt to reconcile his system to the vulgar opinion further than reason supports him.’ He also reports Berkeley’s moves aiming to show that his immaterialism doesn’t have the bad consequences that have been alleged against it. Reid concedes this:] The evidence of an all-governing mind, so far from being weakened, seems to appear in an even more striking light on his hypothesis than on the common one. . . . In all this Berkeley reasons soundly and acutely.

But he seems not to have attended to one uncomfortable consequence of his system—one from which it will be found difficult or even impossible to guard it. I mean this: Although the system leaves us sufficient evidence of a supreme thinking mind, it seems to take away all the evidence we have of other thinking beings like ourselves. What I call my father, my brother, or my friend is only a cluster of ideas in my mind; and such a cluster can’t possibly have to another mind the relation they have to mine, any more than the pain I feel can be the very same individual pain that you feel. I can’t find in Berkeley’s system anything that makes it even probable that there are other thinking beings like myself in the relations of father, brother, friend, or fellow-citizen. I am left alone as the only creature of God in the universe. . . .

Of all the opinions that have ever been advanced by philosophers, Berkeley’s view that there is no material world seems the strangest and the most apt to bring philosophy into ridicule with plain men who are guided by the dictates of Nature and common sense. So it may be worthwhile to trace this offspring of the doctrine of ideas from its birth, and to watch it growing up until it was so strong that a pious and learned bishop, ·Berkeley·, was bold enough to usher it into the world •as demonstrable from universally accepted the principles of philosophy, and •as an admirable device for advancing knowledge and defending religion.

During the reign of the Aristotelian philosophy, men were little disposed to doubt and much disposed to dogmatize! The existence of the objects of sense was held as a first principle; and the accepted doctrine was that the ‘sensible species’ or idea is the very form of the external object, separated from its matter and sent across into the perceiving mind. So in that philosophy there is no hint of scepticism about the existence of matter.

Descartes taught men to doubt even things that had been taken for first principles. He rejected the doctrine of species or ideas coming from objects; but still maintained that what we immediately perceive is not the external object but an idea or image of it in our mind. This led some of his disciples to disbelieve the existence of every created thing in the universe except themselves and their own ideas.

But Descartes himself. . . . was determined to support the existence of matter. To do this consistently with his principles, he found that he had to rely on arguments that are far-fetched and not very strong. Sometimes he argues that our senses are given to us by God, who is not a deceiver; and therefore we ought to believe what they tell us. But this argument is weak, because according to Descartes’s principles our senses tell us only that we have certain ideas. If we infer from this testimony a conclusion that doesn’t really follow from it, we are deceiving ourselves ·rather than being deceived by God·. To strengthen this weak argument Descartes sometimes adds that we have by nature a strong propensity to believe that there is an external world corresponding to our ideas.

Malebranche thought that this strong propensity is not a sufficient reason to believe in the existence of matter; and that it is to be accepted as an article of faith that can’t be established for sure by reason. He is aware that faith comes through hearing, and that it may be said that prophets, apostles, and miracles are only ideas in our minds. But to this he answers that even if those things are only ideas, faith turns them into realities; and this answer he hopes will satisfy those who are not too fastidious!

It may seem strange that Locke, who wrote so much about ideas, didn’t see the consequences that Berkeley thought so obviously deducible from that doctrine. Locke surely didn’t want the doctrine of ideas to be thought to be loaded with such consequences! He acknowledges that the existence of a material world is not to be accepted as a first principle, and that it can’t be demonstrated; but he argues for it as best he can, and makes up for the weakness of his arguments by remarking that we have enough evidence to direct us in pursuing the good and avoiding the harm that external things could do us, beyond which we have no concern.

There is just one passage in Locke’s Essay which may lead one to conjecture that he •had a glimpse of the system that Berkeley afterwards advanced, but •thought proper to keep it to himself. The passage is in Essay IV.x. Having proved the existence of an eternal thinking mind, he comes to answer those who think that matter must also be eternal because we can’t conceive how it could be made out of nothing. After remarking that the creation of minds requires as much power as the creation of matter, he adds this:

Actually, when we think about it we find that the creation of a mind requires as much power as the creation of matter. Indeed, if we were to free ourselves from everyday notions, and raise our thoughts as far as possible to a closer contemplation of things, we might be able to aim at some dim and seeming conception of how matter might at first be made, how it might begin to exist by the power of the eternal first being; whereas to bring a mind into existence would be found a more inconceivable effect of omnipotent power. But this would perhaps lead us too far from the notions on which the philosophy now in the world is built. . . . (Essay IV.x.18)

[Reid offers a close analysis of this passage, suggesting that it hints at something like Berkeley’s system, and concluding:] It seems reasonable to conjecture, from the passage quoted above, that Locke was aware of the ·Berkeleian· consequence of his own views, but left it to those who should come after him to carry his principles their full length after they have become better established and better able to stand the shock of their collision with vulgar notions. [Reid was wrong about this. We now know what Locke had in mind in IV.x.18. For the full story see www.earlymoderntexts.com/jfb/howmat.pdf.]. . . .

So we learn that the doctrine of ideas as it was newly shaped by Descartes looked with an unfriendly eye on the material world; and although philosophers were very unwilling to give up either ·the doctrine or the world·, they found it hard to reconcile them to each other. In this state of affairs, I think Berkeley counts as the first who had the courage to give up the •material world altogether as a sacrifice to the accepted •philosophy of ideas. . . .

Chapter 11: Berkeley’s view about the nature of ideas

I pass over Berkeley’s views about abstract ideas, and about space and time, these being topics that can more properly be considered in another place, ·namely Essay 5·. But I must pay attention to one part of his system, in which he seems to have deviated from the common opinion about ideas.

Though he sets out in his Principles of Human Knowledge by telling us that it is ‘evident’ that the objects of human knowledge are ideas, and builds his whole system on this principle, Berkeley finds as the system develops that certain objects of human knowledge are not •ideas ·that go out of existence when not thought of· but •things that have a permanent existence. The objects of knowledge of which we have no ideas are •our own minds and their various operations, •other finite minds, and •the mind of God. The reason why there can be no ideas of minds and their operations, Berkeley tells us, is this [not a direct quotation from Berkeley]:

Ideas are passive, inert, unthinking things, so they can’t be the image or likeness of things that have thought and will and active power. We have notions of minds and of their operations, but not ideas of them. We know what we mean by ‘thinking’, ‘willing’, and ‘perceiving’; we can reason about beings that have those powers; but we have no ideas of them. A •spirit or mind is the only substance or support in which •unthinking things or ideas can exist; but it would be absurd to suppose that this substance that supports or perceives ideas is itself an idea or like an idea.

He observes further [The parts of this all come from Principles 142, but Reid has altered their order]:

Because all relations include an act of the mind, we can’t properly be said to have an idea of the relations between things or of their relational properties, but rather a notion of them. But if in the modern way ‘idea’ is stretched to cover minds and relations and acts, this is after all a merely verbal matter; though it is clearer and more correct to distinguish very different things by different names.

This is an important part of Berkeley’s system, which deserves our attention. It leads us to divide the objects of human knowledge into two kinds. (1) Ideas, which we have by our five senses; they exist only in the minds of those who perceive them, and don’t exist at all when they aren’t perceived. (2) Minds, their actions, and the relations and relational properties of things. Of these we have notions, but no ideas. No idea can represent them or resemble them. Yet we understand what they—·or rather their names·—mean, and we can speak of them with understanding and can reason about them without ideas.

This account of ideas is very different from Locke’s.

In Locke’s system: We have no knowledge where we have no ideas. Every thought must have an idea as its immediate object.

In Berkeley’s: The most important objects are known without ideas.

In Locke’s system: There are two sources for our ideas— sensation and reflection.

In Berkeley’s: Sensation is the only source for ideas, because there can’t be ideas of the objects of reflection. We know them without ideas.

In Locke’s system: Ideas are divided into those of •substances, •modes, and •relations.

In Berkeley’s: There are no ideas of •substances or of •relations, or even of the operations of our own minds, which are a subset of •modes. Of all these items we have clear notions but no ideas.

[Then a paragraph about the closeness of Malebranche’s system to Berkeley’s, and about ‘whether these two acute philosophers foresaw the consequences that follow from the full-strength system of ideas’. Then:]

Be that as it may, if so many things can be thought about and known without ideas, this naturally suggests a doubt about the rest. It may be asked:

If we can think and reason about the •world of minds without ideas, mightn’t we be able to think and reason about a •material world without ideas? If consciousness and reflection provide us with notions of minds and of their attributes, without ideas, mightn’t our senses provide us with notions of bodies and their attributes, without ideas?

Berkeley foresaw this objection to his system, and puts it into Hylas’s mouth thus:

If you can have a thought about the mind of God without having an idea of him, then why can’t I conceive the existence of matter without having an idea of it?

Philonous replies:

(i) You don’t perceive matter objectively, as you do an inactive being or idea; (ii) nor do you know it, as you know yourself, by an act of mentally attending to yourself. (iii) You don’t understand it indirectly, through a resemblance between it and either your ideas or yourself; and (iv) you don’t bring it into your mind by reasoning from what you know immediately. All of this makes the case of matter widely different from that of the Deity, ·because your knowledge of him involves (iii) and (iv)·.

[Berkeley was using ‘objectively’ in its older meaning of ‘by mental representation’. Reid seems to take it to mean ‘accurately’ or ‘realistically’, a meaning that is closer to the one we have today.]

Though Hylas says he is satisfied with this answer, I confess that I am not! If I can trust the faculties that God has given me, I do perceive matter objectively—i.e. as something that is extended and solid, that can be measured and weighed, and that is the immediate object of my touch and sight. And I take this object to be •matter, not an •idea. Philosophers tell me that what I immediately touch is an idea, not matter; but I have never been able to confirm this by the most careful attention to my own perceptions.

I wish this ingenious author had explained what he means by ‘ideas’ as distinct from ‘notions’. The word ‘notion’ is well understood as a word in ordinary language. What everyone means by it is the conception, the apprehension, the thought that we have of some object of thought. So a notion is something the mind does in conceiving or thinking of some object. The object of the thought may be in the mind, or not in the mind. It may be something that has no existence ·at any time·, or something that did or does or will exist. But the notion that I have of that object is an act of my mind—it really exists while I think of the object, but doesn’t exist when I don’t think of it. In ordinary speech ‘idea’ means exactly the same as ‘notion’; but philosophers have another meaning for ‘idea’, and it’s hard to say what that meaning is.

The whole of Berkeley’s system depends on the distinction between notions and ideas; so it will be time well spent if we can discover what the things are that he calls ‘ideas’ as distinct from ‘notions’.

Notice first that he recognizes two kinds of ideas—ideas of •sense and ideas of •imagination:

The (1) ideas imprinted on the senses by the author of Nature are called ‘real things’; and those (2) that are caused by the imagination, being less regular, vivid, and constant, are more properly called ‘ideas’ or ‘images’ of things that they copy and represent. But our (1) sensations, however vivid and distinct they may be, are nevertheless ideas; that is, they exist in the mind, or are perceived by it, as truly as (2) the ideas that mind itself makes. The (1) ideas of sense are agreed to have more reality in them—that is, to be more strong, orderly, and coherent than ideas made by the mind. They are also less dependent on the mind or thinking substance that perceives them, for they are caused by the will of another and more powerful mind, ·namely God·; but still they are ideas, and certainly no idea—whether faint or strong—can exist otherwise than in a mind perceiving it.

This passage shows us that by ‘ideas of sense’ the author means sensations. And this is also evident from many other passages. [Reid also offers brief quotations from Berkeley’s Principles sections 5, 18, and 25. The long passage quoted above is from 33.

It seems certain, therefore, that by ‘ideas of sense’ the author meant sensations that we have through our senses. I have tried to explain the meaning of ‘sensation’ in Essay 1, chapter 1 [item 12]; and that explanation appears to me to fit perfectly with the sense in which Berkeley uses the word.

Just as there can be no notion or thought except in a thinking being, so also there can be no sensation except in a sentient being. A sensation is the act or feeling of a sentient being, and its very essence consists in its being felt. Nothing can resemble a sensation except a similar sensation in the same mind or in some other mind. To think that any quality of an inanimate thing can resemble a sensation is a great absurdity. In all this I have to agree perfectly with Berkeley; and I think his notions of sensation are much clearer and more accurate than Locke’s—who thought that the primary qualities of body do resemble our sensations while the secondary ones don’t.

‘We have many sensations by means of our external senses’—there can be no doubt about that; and if Berkeley chooses to call those sensations ‘ideas’, there ought to be no dispute about the meaning of a word. But, he says, by our senses we have the knowledge only of our sensations—or ‘ideas’, call them what you like. I allow Berkeley to call them what he likes; but please give due weight to the word ‘only’ in the foregoing sentence, because a great deal depends on it.

If it’s true that our senses can give us knowledge only of our sensations, then his system must be accepted and the existence of a material world given up as a dream. No demonstration can be more secure than this. If we have any knowledge of a material world it must be by the senses. But the senses give us knowledge of nothing but our sensations; and they don’t resemble anything that can exist in a material world. The only questionable proposition in this demonstration is ‘The senses give us knowledge of nothing but our sensations’. If there are objects of the senses that are not sensations, Berkeley’s arguments don’t touch them; they may be things that don’t exist in the mind as all sensations do; they may be things of which our senses give us notions though no ideas; just as by consciousness and reflection we have notions of minds and of their operations without ideas or sensations.

[Then a short paragraph in which the discussion of ‘notions’ leads, by a scarcely followable route, to the thesis that •ideas of sensation are •sensations. Reid continues:] Let us hear the dictates of common sense on this point.

Suppose I am pricked with a pin. Is the pain I feel a sensation? It certainly is! There can’t be anything that resembles pain in any inanimate thing. Is the pin a sensation? I have to answer that it isn’t a sensation and can’t have the least resemblance to any sensation. The pin has length and thickness and shape and weight, whereas a sensation can’t have any of those qualities. I am as certain that the pin is not a sensation as I am that the pain I feel is a sensation; yet the pin is an object of sense; and I am as certain that •I perceive its shape and hardness by my senses as that •I feel pain when pricked by it.

Having said that much about the ideas of sense in Berkeley’s system, we should now consider his account of ideas of imagination. About these he says:

I find I can arouse ideas in my mind at will, and vary and shift the mental scene whenever I want to. I need only to will, and straight away this or that idea arises in my mind; and by willing again I can obliterate it and bring on another. It is because the mind makes and unmakes ideas in this way that it can properly be called active. It certainly is active; we know this from experience. (Principles 28)

And five sections earlier he says that our sensations are called ‘real things’, and that the ideas of imagination are more properly termed ‘ideas’ or ‘images’ of things—which presumably makes them images of our sensations. Given that the ideas of imagination are made by us, one would expect that we’d be well acquainted with them; and yet after all that Berkeley said about them I am at a loss to know what they are.

First point: these ideas of imagination are not sensations. For surely sensation is the work of the senses, not of imagination; and though pain is a sensation, my thought of pain when I am not in pain is not a sensation.

Second point: I can’t find any difference between •ideas of imagination and •notions, though Berkeley says that the latter are not ideas. I can easily distinguish a notion from a sensation. Having the sensation of pain is one thing; having a notion of pain is another. Having a notion of pain is merely understanding what ‘pain’ means, whereas having the sensation of pain is really feeling pain. But I can’t find any difference between the •notion of pain and the •imagination of pain—or indeed between the notion of anything and the imagination of it. So I can’t give any account of Berkeley’s distinction between •ideas of imagination and •notions, which he says are not ideas. They seem to me to coincide perfectly.

He does indeed seem to say that ideas of imagination differ from those of the senses not in •kind but only in their •degree of regularity, liveliness, and constancy (Principles 30). This doctrine was later greedily embraced by Hume, who used it as a main pillar of his system; but it can’t be reconciled to common sense, for which Berkeley claims to have great respect. For according to this doctrine, if we compare •the state of a man racked by the gout with •his state when he comfortably tells us about what he has suffered, the only difference between these two states is that in the latter the pain is less regular, vivid, and constant than in the former. We can’t possibly assent to this. Everyone knows •that he can report a pain that he suffered ·at some past time· not only without pain but with pleasure, and •that suffering pain and •thinking about pain are totally different in kind, not merely in degree.

Summing up: We see that according to Berkeley’s system we have no ideas at all of the most important objects of knowledge, i.e. minds, their operations, and the relations among things; we have •notions of these but not •ideas. The ideas we do have are ideas of •sense and of •imagination. The •former are the sensations we have by means of our senses, whose existence everyone must admit because he is conscious of them, and whose nature Berkeley has explained with great accuracy. As to •ideas of imagination, he has left us much in the dark. He makes them images of our sensations, though according to his own doctrine nothing can resemble a sensation but a sensation. [Reminder: In Reid’s day the core meaning of ‘image of x’ was ‘likeness of x’.] He seems to think that they differ from sensations only in their degree of regularity, liveliness, and constancy. But this can’t be reconciled to the experience of mankind. . . . Indeed, the very reason he gives why we can’t have ideas of mental acts or of the relations of things applies also to what he calls ideas of imagination:

Although it is not strictly right to say that we have an idea of an active being or of an action, we can be said to have a notion of them. I have some knowledge or notion of my mind and of how it acts with regard to ideas, in that I know or understand what is meant by those words. Also, since all relations include an act of the mind, we ought strictly speaking to be said to have not an •idea but rather a •notion of the relations between things and of their relational properties. (Principles 142)

This implies that our imaginings are not strictly •ideas but •notions, because they ‘include an act of the mind’. For Berkeley tells us in a passage I have already quoted that they are creatures of the mind’s own making, that it makes and unmakes them as it thinks fit, and that that’s why it is properly called ‘active’. . . .

When so much has been written and so many disputes raised about ideas, it would be good if we knew what they are, what category or class of beings they belong to. We might think that Berkeley would tell us this, given his known accuracy and precision in the use of words; and that is why I have taken so much trouble to find out what he took ideas to be. ·Here, in summary, is what I have come up with·:

(1) If I understand what he calls ‘ideas of sense’, they are the sensations we have by means of our five senses; but he says that ‘ideas’ is a less proper name for them.

(2) I also understand what he calls ‘notions’, but he says that they are very different from ideas, though these days they are often called by that name.

(3) That leaves ‘ideas of imagination’, which Berkeley says are the things most properly called ‘ideas’. I am still very much in the dark about these. When I imagine a lion or an elephant, •the lion or elephant is the object imagined. •The act of the mind in conceiving that object is the notion, conception or imagination of the object. If besides •the object and •the act of the mind concerning it there is some ·third· thing called the •idea of the object, I don’t know what it is.

If we consult other authors who have discussed ‘ideas’ we’ll get no more help regarding the meaning of this philosophical term. The vulgar have adopted it; but all they mean by ‘idea’ is the notion or conception we have of a object, especially our more abstract or general notions. When ‘idea’ is used in this way to signify the mind’s operation on objects—conceiving, remembering, or perceiving—it is well understood. But philosophers insist that ideas are the objects of the mind’s operations and not the operations themselves. There is indeed great variety of objects of thought. We can think about minds and their operations, and about bodies and their qualities and relations. If ideas are not included in any of these classes, I am at a loss to understand what they are.

In ancient philosophy, ideas were said to be immaterial forms that exist from all eternity (according to one system) or are sent out from the objects whose form they are (according to another). In modern philosophy they are things in the mind that are the immediate objects of all our thoughts, having no existence when we don’t think of them. They are called the ‘images’, ‘resemblances’, or ‘representatives’ of external objects of sense; yet they don’t have colour or smell or shape or motion or any sensible quality! I respect the authority of philosophers, especially when they are so unanimous; but until I can understand what •they mean by ‘idea’ I must think and speak with •the vulgar. [This alludes to Berkeley’s remark that on some of these matters we should ‘think with the learned and speak with the vulgar’.]

In sensation, properly so-called, I can distinguish two things—the •mind or sentient being and the •sensation. I am not going to argue about whether the sensation is to be called a ‘feeling’ or an ‘operation’, but ·I do assert· that its only object is the sensation itself. If sensation involves a third thing called an •‘idea’, I don’t know what that is.

In perceiving, remembering, conceiving, and imagining I can distinguish three things: •the mind that operates, •the operation of the mind, and •the object of that operation. The perceived object is one thing and the perception of it another—I am as certain of that as I can be of anything. The holds also for conception, remembering, love and hatred, desire and aversion. In all these the act of the mind about its object is one thing and the object is another. There must be an object, real or imaginary, that is distinct from the operation of the mind concerning it. Now if in these operations the ‘idea’ is a fourth thing, different from the three I have mentioned, I don’t know what it is, and haven’t been able to learn from all that has been written about ideas. . . .

Chapter 12: Hume’s views

Two volumes of the Treatise of Human Nature were published in 1739 and the third in 1740. The doctrine contained in this Treatise was published in a more popular form in Hume’s Philosophical Essays, of which there have been several editions. [Hume died about eight years before the present work appeared.] What other authors from Descartes on had called ‘ideas’ Hume distinguishes into two kinds:

•impressions, including all our sensations, passions, and emotions; and

•ideas, including the faint images of impressions when we remember or imagine them.

He sets out with a principle that he doesn’t offer to prove because he thinks it doesn’t need one, namely:

All the perceptions of the human mind come down to these two kinds—•impressions and •ideas.

This proposition is the foundation on which the whole of Hume’s system rests, and from which it is built with great acuteness and ingenuity; so we might wish that he had told us what his authority was for it. But ·he doesn’t; he· leaves us to guess whether it is offered as a self-evident first principle or rather is to be accepted on the authority of philosophers.

Locke had taught us that all the immediate objects of human knowledge are ideas in the mind. Berkeley working from this same basis easily demonstrated that there is no material world. He thought that for the purposes both philosophy and religion we would find no loss but great benefit in getting rid of the material world. But. . . .he was unwilling to give up the world of ·minds or· spirits. He clearly saw that ideas are no more fit to represent minds than they are to represent bodies. Perhaps he saw that if we perceived only ideas of minds, we couldn’t infer their real existence from the existence of their ideas, any more than we can infer the existence of matter from the idea of it; and so, while he gives up the material world in favour of the system of ideas, he gives up half of that system in favour of the world of minds; and maintains that we don’t need ideas to think, speak, and reason intelligibly about minds and their qualities and operations.

Hume shows no such bias in favour of the world of minds. He adopts the whole theory of ideas, ·not just Berkeley’s half of it·; and that enables him to ‘show’ that the universe contains no matter and no minds—nothing but impressions and ideas. What we call a ‘body’ is only a bundle of sensations; and what we call the ‘mind’ is only a bundle of thoughts, passions, and emotions, without any subject. ·i.e. without any thing that has the thought, passion or emotion·. . . .

When a system of consequences is intelligently and soundly inferred from a few very abstract principles, that is of real utility in science and may be a help towards gaining real knowledge; and this is true even if the inferred system is in itself absurd. Hume’s metaphysical writings have this merit in high degree. . . .

It is amusing to consider that while philosophers have been labouring by means of ‘ideas’ to explain perception and the other operations of the mind, those ideas have gradually usurped the place of perception, object, and even the mind itself, supplanting the very things they were introduced to explain! Descartes reduced all the operations of the understanding to •perception, which is natural for someone who believes that those operations are only different ways of •perceiving ideas in our own minds. Locke runs •ideas together sometimes with the •perception of an external object and sometimes with the •external object itself. In Berkeley’s system the idea is the only object, and yet it is often run together with the perception of it. But in Hume’s system the idea—or the impression, which is only a more lively idea—is mind, perception, and object all in one! So that by the term ‘perception’ in Hume’s system we must understand

•the mind itself; •all its operations, both of understanding and will; and •all the objects of these operations.

With ‘perception’ taken in this sense, he divides perceptions into our more lively perceptions, which he calls impressions, and the less lively ones, which he calls ideas. For comments, look back at what I said in Essay 1, chapter 1 about the meanings of the words ‘perceive’ [item 6], ‘object’ [item 9] and ‘impression’ [item 11].

Philosophers have differed greatly with regard to the origin of our ideas, the sources from which they are derived. The Aristotelians held that all knowledge initially comes from the senses, and this ancient doctrine seems to be revived by some recent French philosophers and by Hartley and Priestley among the British. Descartes maintained that many of our ideas are innate. Locke energetically opposed the doctrine of innate ideas, employing the whole of Essay I against it. But he allows two different sources of ideas, sensation and reflection. . . . The main purpose of Essay II is to show that absolutely all our simple ideas come from the one or other or both of these sources. This leads Locke into some paradoxes, although in general he doesn’t care for paradoxes. And if he had foreseen all the consequences that can be inferred from his account of the origin of our ideas, he would probably have examined it more carefully!

Hume adopts Locke’s account of the origin of our ideas, and infers from it that we have no idea of substance, bodily or mental; no idea of power; no idea of cause of x except the idea of something that occurs before x does and is constantly conjoined with it; in short that we can have no idea of anything except our sensations and the operations of mind that we are conscious of.

He doesn’t grant to the mind any power in forming its ideas and impressions; and that’s not surprising, because he holds that we don’t have any idea of power, and the mind is nothing but the sequence of impressions and ideas of which we are intimately conscious.

So he thinks that our impressions arise from unknown causes, and that the impressions are the causes of their corresponding ideas. All he means by this is that they always go before the ideas; for ·according to him· that’s all that is needed to constitute the relation of cause and effect.

As for the order and succession of our ideas, he thinks that that is governed by •three laws of attraction or association, which he takes to be basic properties of the ideas—properties that lead ideas to attract (so to speak), or associate themselves with, other ideas that either •resemble them or •have been contiguous to them in time and place or •are related to them by the relations of cause and effect. (Actually, the second of these seems to include the third, since according to Hume causation implies nothing more than contiguity in time and place.). . . .

Chapter 13: Arnauld’s views

In this sketch of philosophers’ opinions about ideas we must not omit Antoine Arnauld, doctor of the Sorbonne, who in the year 1683 published his book True and False Ideas in opposition to the system of Malebranche that I have described. I couldn’t find this book until about ten years ago; I believe it is rare.

Though Arnauld wrote before Locke, Berkeley and Hume, I have kept until last my account of his views, because I find it hard to determine whether he •adopted the common theory of ideas or whether he is on his own in rejecting it altogether as a fiction of philosophers. [’Common theory’ is explained here.]

The controversy between Malebranche and Arnauld inevitably led them to consider what kind of things ideas are—a point on which other philosophers had very generally been silent. Both of them proclaimed the universally accepted doctrine •that we don’t perceive material things immediately, •that the immediate objects of our thought are their ideas, and •that it is in the idea of any thing that we perceive its properties.

I should explain at the outset that both these authors use ‘perception’ as Descartes had done before them—namely, to signify every operation of the understanding. ‘To think, to know, to perceive, are the same thing’, says Arnauld. I should also note that they both call the various operations of the mind ‘modifications’ of the mind. [’Modification’ means ‘state or quality or property’. The force of saying that thinking is a modification of the mind is that the rock-bottom truth about a given mind’s thinking has the form it thinks, not it performs a thought, suggesting that the mind stands in a certain relation to something other than itself.]. . . .

·ARNAULD’S TARGET: MALEBRANCHE·

The things that the mind perceives, says Malebranche, are of two kinds: they are either •in the mind itself or •external to it. The things in the mind are all its different modifications—its sensations, imaginations, pure thinkings, passions, and affections. These are immediately perceived: we are conscious of them, and have no need of ideas to represent them to us.

Things external to the mind are either bodily or mental, With regard to mental objects of thought, he thinks it possible that in another state ·after death· minds may become immediate objects of our understandings, and thus be perceived without ideas; and that ·even now higher-thanhuman· spirits may immediately perceive each other and communicate their thoughts back and forth without signs and without ideas.

But leaving this as an open question, he holds it to be undeniable that material things can’t be perceived immediately but only by the mediation of ideas. He thought it likewise undeniable that the idea must be immediately present to the mind, that it must touch the soul (as it were) and affect its perception of the object.

These principles force us to choose: either the idea is some modification of the human mind or it is an idea in the divine mind that is always intimately present to our minds. Having reached this parting of the ways, Malebranche first considers all the possible ways such a modification may be produced in our mind as the item we call an ‘idea of a material object’—always taking it for granted that it must be an •object that is perceived, something different from the mind’s •act in perceiving it. He finds insuperable objections against every hypothesis about how such ideas might be produced in our minds, and therefore concludes that the immediate objects of perception are the ideas in the mind of God.

·ARNAULD ATTACKS THE TARGET·

Against this system Arnauld wrote his book True and False Ideas. He doesn’t bring objections against Malebranche’s parting of the ways, but he maintains •that ·at this fork in the road Malebranche took the wrong direction, i.e. •that· ideas are modifications of our minds. And when he looks for a modification of the human mind that could be called ‘idea of an external object’, the only one he can find is perception.

I take the •idea of an object and the •perception of an object to be the same thing. There may be other things to which the name ‘idea’ could also be given. But it is certain that there are ideas in this sense of ‘idea’, and that these ideas are either attributes or modifications of our minds.

This, I think, attacked Malebranche’s system on its weak side, which was also the side on which an attack was least expected. Philosophers had been so unanimous in maintaining that we don’t perceive external objects immediately, but only by certain representative images of them called ‘ideas’, that Malebranche might well think his system was safe on that flank, and that the only remaining question was: In what subject—·what thinking substance·—are those ideas located—the human mind or God’s mind?

But, says Arnauld, those ‘ideas’ are mere chimeras— fictions of philosophers; there are no such things in Nature; so that no question arises as to whether they are in the divine or in the human mind. The only true and real ideas are our perceptions, which all philosophers (including Malebranche) agree are acts or modifications of our own minds. . . .

Of all the powers of our mind, the external senses are thought to be the best understood and their objects are the most familiar. Hence we think of other powers in terms of the external senses, and transfer to other powers the language that properly belongs to them. ·Here is an example of such a transfer·. An object of the senses can’t be perceived unless it is •present to the ·relevant· sense or •within its sphere. This leads us to say, by analogy, of anything that we are thinking about that it is ‘present’ to the mind or is ‘in’ the mind. But this ‘presence’ is only metaphorical or analogical; and Arnauld calls it ‘objective presence’ to distinguish it from the local presence that is required in objects that are perceived by sense. But because both are called by the same name, they come to be run together, and things that belong only to real or local presence are attributed also to the metaphorical ‘presence’. [In this context, ‘objective’ is used in a sense that it did once have, to mean something like ‘representative’—something is ‘objectively present in the mind’ if the mind is thinking about it. (See here.) ‘Local presence’ is just presence in the most literal sense, in which something’s being present to my mind depends on where it is, its location.]

Similarly, we are accustomed to seeing objects by their images in a mirror or in water; which leads us by analogy to think that objects can be presented to the memory or imagination in some similar manner, through images that philosophers have called ‘ideas’.

By such prejudices and analogies, Arnauld thinks, men have been led to believe that the objects of memory and imagination must be presented to the mind by images or ideas; and philosophers have been more carried away by these prejudices than even the vulgar, because they could use this theory to ‘explain’ the various operations of the mind—a matter in which the vulgar take no interest.

But he thinks that Descartes overcame •these prejudices, and that he used ‘idea’ to signify the same thing as ‘perception’, so he was surprised that an admiring disciple of Descartes such as Malebranche was carried away by •them. It is strange indeed that the two most eminent disciples. of Descartes and his contemporaries should differ so crucially regarding his doctrine about ideas.

I shan’t try to tell you how this controversy between those two acute philosophers developed in the subsequent defences and replies, because I haven’t been able to see them. ·All I know about them is that· after much reasoning and some animosity, each continued in his own opinion and left his antagonist where he found him. Malebranche’s view that we see all things in God soon died away of itself; and Arnauld’s notion of ideas seems to have been given less attention than it deserved by the philosophers who came after him—perhaps in part because he seems in a way to have relinquished it by trying to reconcile it to the common doctrine concerning ideas.

[Reid then spends more than a page giving textual evidence of Arnauld’s trying to reconcile his position with ‘the common doctrine’. He ends the chapter thus:]

Summing up: If Arnauld had taken his stand on his doctrine that ideas considered as representative images of external objects are a mere philosophers’ fiction, and had boldly rejected •the doctrine of Descartes as well as of the other philosophers concerning those fictitious beings and •all the ways of speaking that imply their existence, I would have thought him more self-consistent, and his doctrine concerning ideas more rational and intelligible, than that of any other author I know of who has discussed this subject.

Chapter 14: Thoughts about the common theory of ideas

After such a long account of the views of philosophers ancient and modern concerning ideas, it may seem presumptuous to question whether ideas exist! But no philosophical opinion, however ancient and however generally accepted, ought to rest on authority. It isn’t presumptuous to require evidence for it, or to let our belief be governed by the evidence we can find.

Please bear in mind: If by ‘ideas’ are meant only the •acts or operations of our minds in perceiving, remembering, or imagining objects, I am far from questioning their existence; we are conscious of those •acts every day and every hour of our lives, and I don’t think any sane man ever doubted the real existence of the mental operations of which he is conscious. Nor is it to be doubted that the faculties God has given us enable us to conceive things that are absent as well as to perceive things that are within the reach of our senses, and that such conceptions can be more or less distinct, and more or less lively and strong. We have reason to ascribe to God distinct conceptions of all things existent and possible, and of all their relations; and if these conceptions are called his eternal ‘ideas’, there ought to be no dispute among philosophers about a word. The ‘ideas’ of whose existence I require proof are not •the operations of any mind but the supposed •objects of those operations. . . .

Nor do I dispute the existence of what the vulgar call ‘objects of perception’. Everyone who acknowledges the existence of these calls them ‘real things’, not ‘ideas’. But philosophers maintain that in addition to these there are immediate objects of perception in the mind itself, ·and that is what I am disputing·. . . . [Then a paragraph making the same point about objects of remembering and imagining. Then:]

My first thought about this philosophical opinion is that it is directly contrary to the sense of everyone who hasn’t been instructed in philosophy. When we see the sun or moon, we have no doubt that the very objects that we immediately see are far from us and from one another, and that this is the sun and moon that God created some thousands of years ago and that have continued to move around in the heavens ever since. How astonished we are when the philosopher tells us that we are wrong about all this, that the sun and moon that we see are. . . .in our own mind, and that they didn’t exist before we saw them and won’t exist after we stop perceiving and thinking about them!. . . .

If a plain man uninstructed in philosophy has faith to accept these mysteries, how astonished he must be! He is brought into a new world where everything he sees, tastes, or touches is an idea—a fleeting kind of thing that he can conjure into existence or annihilate in the twinkling of an eye.

After he has calmed down, it will be natural for him to ask his philosophical instructor: ‘Please, sir, are there then no substantial and permanent things called the “sun” and “moon”, things that continue to exist whether or not we think about them?’

Here the philosophers differ. Locke and his predecessors will answer: ‘Indeed there are substantial and permanent beings called the “sun” and “moon”; but they never appear to us in their own right, but only through their representatives— the ideas in our own minds—and we know nothing about them except what we can gather from those ideas.’

Berkeley and Hume would give a different answer to the question. They would assure the questioner that it is a vulgar error, a mere prejudice of the ignorant and uneducated, to think that there are any permanent and substantial beings called the ‘sun’ and ‘moon’; that the heavenly bodies, our own bodies, and all bodies whatsoever, are nothing but ideas in our minds; and that ·they can’t •represent anything outside us because they can’t •resemble anything outside us, because· nothing can be like the ideas of one mind but the ideas of another mind. . . .

In this representation of the theory of ideas I don’t think I have exaggerated or misrepresented anything; and surely that is enough to show that to the uninstructed in philosophy the theory must appear extravagant and visionary and utterly contrary to the dictates of common understanding.

There is little need for any further proof of this because it is amply acknowledged by Hume:

It seems clear that we humans are naturally, instinctively inclined to trust our senses, and that without any reasoning—indeed, almost before the use of reason—we take it that there is an external universe that doesn’t depend on our perceiving it and would have existed if there had never been any perceiving creatures or if we had all been annihilated. Even the animals are governed by a similar opinion, and maintain this belief in external objects in all their thoughts, plans and actions.

It also seems clear that when men follow this blind and powerful instinct of Nature they always suppose that •the very images that their senses present to them are •the external objects that they perceive; it never crosses their minds that •sensory images are merely representations of •external objects. This very table that we see as white and feel as hard is believed to exist independently of our perception, and to be something external to our mind that perceives it. Our presence doesn’t bring it into existence, and our absence doesn’t annihilate it. It stays in existence (we think), complete and unchanging, independent of any facts about intelligent beings who perceive it or think about it.

But the slightest philosophy is enough to destroy this basic belief that all men have. For philosophy teaches us that images (or perceptions) are the only things that can ever be present to the mind, and that the senses serve only to bring these images before the mind and cannot put our minds into any immediate relation with external objects. (Enquiry Concerning Human Understanding, section 12)

So Hume acknowledges that there is a natural instinct or assumption, a universal and basic opinion of all men, a primary instinct of Nature, that what we immediately perceive by our senses are not images in our minds but external objects, and that their existence is independent of us and our perception.

In this acknowledgement Hume seems to me more giving and even more honest than Berkeley, who tries to persuade us that his opinion doesn’t oppose the vulgar opinion but only that of the philosophers; and that the external existence of a material world is a philosophical hypothesis and not the natural dictate of our perceptive powers. Bishop Berkeley is nervous about confronting such an adversary as a primary and universal opinion of all men, and tries to persuade it to support him. But philosopher Berkeley boldly defies this antagonist, and seems to glory in a conflict that was worthy of his arm. . . . After all ·that fuss·, I suspect that a philosopher who wages war with this adversary will find himself in the same fix as a mathematician trying to demonstrate that there is no truth in the axioms of mathematics.

My second thought on this topic is this: The authors who have discussed ideas have generally taken their existence for granted, as something that couldn’t be called in question; and such arguments as they have casually introduced in order to prove it seem too weak to support the conclusion.

Locke in the introduction to his Essay tells us that he uses ‘idea’ to signify whatever is the immediate object of thought, and then he adds: ‘I presume it will be easily granted me that there are such ideas in men’s minds; everyone is conscious of them in himself, and men’s words and actions will satisfy him that they are in others as well.’ (Essay I.i.8) I am indeed ‘conscious of’ perceiving, remembering, imagining; but I am not conscious that the objects of these operations are images in my mind. I am satisfied by men’s words and actions that they often perceive the same objects that I perceive, which they couldn’t do if the objects I perceive were ideas in my own mind.

[Then a paragraph reporting on and criticising Norris’s four arguments for the thesis that material things couldn’t be perceived immediately. Reid says that they are respectively ‘lame’, unintelligible, irrelevant, and ‘mysterious’. Then:]

An argument that is hinted at by Malebranche and by several other authors deserves to be more seriously considered. I find it most clearly expressed and most strongly urged by Clarke; so I shall give it in his words:

The soul could not possibly perceive anything without being present to an image of it. A living substance can’t perceive •anywhere unless it is present •there—present either to the things themselves, as the omnipresent God is to the whole universe, or to the images of things, as the soul is in its sensorium, ·i.e. in the part of the brain where it is located·. (Leibniz-Clarke Correspondence, Clarke’s second reply)

Newton expresses the same opinion, though with his usual reserve he expresses it only as a question.

The ingenious William Porterfield adopts this opinion with more confidence:

Nothing can act or be acted on at a place where it doesn’t exist; therefore our mind can never perceive anything but its own states and the various states of the sensorium to which it is present. So what our mind perceives are not the external sun and moon up in the sky but only their image or representation impressed on the sensorium. How the soul sees these images—how it receives those ideas from such agitations in the sensorium—I don’t know; but I am sure that it can never perceive the external bodies themselves, bodies to which it is not present. (Medical Essays and Observations, vol. 3)

These are indeed great authorities, but in matters of philosophy we should be guided not by authority but by reason. . . . I think we must accept that

•Nothing can act immediately in a place where it doesn’t exist;

for I agree with Newton that •power without substance is inconceivable, from which it follows that •nothing can be acted on immediately at a place where the agent—·the substance that acts·—is not present. To reach the conclusion of the ·Clarke-Porterfield· argument, however, another premise is needed, namely:

•When we perceive objects, either they act on us or we act on them.

This doesn’t look self-evident, and I have never seen any argument for it. I shall briefly present the reasons why I think it ought not to be accepted.

When we say that x ‘acts on’ y, we mean that x exerts some power or force that produces or tends to produce a change in y. . . . So there seems to be no reason to say that in perception either (1) the object acts on the mind or (2) the mind acts on the object.

(1) An object in being perceived doesn’t act at all. I perceive the walls of the room I am sitting in; but they are completely inactive, and therefore are not acting on my mind. Being perceived is what logicians call an ‘external denomination’, ·a purely relational property·, which implies neither action nor quality in the object perceived. ·Something can go from being perceived to not being perceived without undergoing any change in itself—like an author’s going from being neglected to not being neglected simply because his works have started to attract attention on the other side of the world without his even knowing about it·. No-one would have bought into this notion that perception arises from the perceived object’s acting on the mind if we weren’t so prone to form our notions of the mind on the basis of some similarity we think it has to bodies:

•thought in the mind is thought of as analogous to motion in a body;

•what starts a body moving is its being acted on by some other body;

so we are inclined to infer, analogically, that

•what starts the mind perceiving is some impulse it receives from the object.

But reasonings drawn from such analogies ought never to be trusted. They are indeed the cause of most of our errors regarding the mind. We might as well conclude that minds can be measured in feet and inches, or weighed by ounces or grams, because bodies can!

(2) I see as little reason to believe that in perception the mind acts on the object: perceiving an object is one thing; acting on it is another, and isn’t any part of perceiving. To say ‘I act on the wall by looking at it’ is a meaningless misuse of language. . . .

So we have no evidence that in perception the mind acts on the object or vice versa, but strong reasons to the contrary; so Clarke’s argument against our immediately perceiving external objects collapses.

Like many other prejudices, this notion that in perception the object must be contiguous to—·spatially right up against·—the percipient seems to be borrowed from analogy. In all the external senses there must be some impression made on the organ of sense by the object itself or by something coming from it [see chapter 2]; and an impression requires contiguity. So we are led by analogy to conceive something similar in the operations of the mind. Many philosophers analyse almost all operations of the mind into ‘impressions’ and ‘feelings’—words that are obviously borrowed from the sense of touch. And it is very natural to think that there must be contiguity between the thing that makes the impression and the thing that receives it, between the thing that is felt and the thing that feels. No philosopher these days will offer to justify such analogical reasoning as this, but it still has a powerful influence on our judgment. . . .

When we set aside those analogies and reflect attend to our perception of the objects of sense, we must admit that though we are conscious of perceiving objects we are ignorant of how this happens. . . . And if we do admit an image in the mind or right up against it, we have no more idea of •how perception could be produced by this image than we have of •how it could be produced by the most distant object. . . .

I have been able to find only one other argument against our perceiving external objects immediately. It is proposed by Hume, who accepts that all men have a basic belief that we perceive external objects immediately, and then adds this:

But the slightest philosophy is enough to destroy this basic belief that all men have. For philosophy teaches us that images (or perceptions) are the only things that can ever be present to the mind, and that the senses serve only to bring these images before the mind and can’t put our minds into any immediate relation with external objects. The table that we see seems to shrink as we move away from it; but the real table that exists independently of us doesn’t alter; so what was present to the mind was not the real table but only an image of it. These are the obvious dictates of reason; and no-one who thinks about it has ever doubted that when we say ‘this house’ and ‘that tree’ the things we are referring to are nothing but perceptions in the mind—fleeting copies or representations of other things that are independent of us and do not change. To that extent, then, reason compels us to contradict or depart from the basic instincts of Nature, and to adopt a new set of views about the evidence of our senses. (Enquiry 12)

This puts all mankind into a remarkable conflict between two contradictory opinions. On one side stand all the vulgar—·all the men in the street·—who are unpractised in philosophical researches and are guided by the uncorrupted basic instincts of Nature. On the other side stand all the philosophers, ancient and modern—every single man who reflects. In this division I find to my great humiliation that I am grouped with the vulgar!

The passage quoted above is the only one I have found in Hume’s writings on this point; and there is indeed more reasoning in it than I have found in any other author; so I shall examine it in detail. ·My examination will have five main points·.

(1) He tells us that ‘the slightest philosophy is enough to destroy this basic belief that all men have. For philosophy teaches us that images (or perceptions) are the only things that can ever be present to the mind’. The phrase ‘be present to the mind’ has some obscurity, but I think he means ‘is an immediate object of thought’—for instance an immediate object of perception or memory or imagination. If this is the meaning (and it’s the only relevant one I can think of), then all this passage does is to assert the proposition to be proved and assert that philosophy teaches it. If that is right, I beg leave to dissent from philosophy until it gives me some reason for what it teaches. •Common sense and my •external senses demand my assent to their dictates on their own authority, but •philosophy is not entitled to this privilege! Still, I don’t want to dissent from such a grave personage as Philosophy without giving a reason, so I give this reason: I see the sun when it shines, and I remember the battle of Culloden; and neither the sun nor the battle is an image or perception.

He tells us in the next place that ‘the senses serve only to bring these images before the mind’. I know that Aristotle and the schoolmen taught that images or ‘species’ flow from objects, are let in by the senses, and strike on the mind; but this has been so effectively refuted by Descartes, Malebranche, and many others that nobody now defends it. Reasonable men regard it as one of the least intelligible and least meaningful parts of the ancient system. Then what makes modern philosophers—not just Hume—so prone to slide back into this hypothesis as though they really believed it? I think it is because images in the mind and images let in by the senses are so nearly allied and so strictly connected that they must stand or fall together. The ancient system consistently maintained both, whereas the new system has rejected the doctrine of images let in by the senses while still holding that there are images in the mind. Then, once they have made this unnatural divorce of two doctrines that ought to stay married, the one they have retained often leads them back involuntarily to the one they have rejected—·and so we find them writing as though they were Aristotelians·.

Hume surely didn’t seriously believe that an image of sound is let in by the ear, an image of smell by the nose, images of hardness and softness by the ·sense of· touch. For one thing, this is just absurd, as I have shown repeatedly. And anyway Hume and all modern philosophers maintain that the images that are the immediate objects of perception don’t exist when they are not perceived; but if they were let in by the senses they would have to exist before being perceived, and would have an existence independent of the perceiving mind.

Hume tells us further that philosophy teaches that ‘the senses can’t put our minds into any immediate relation with external objects’. I still want to know what reasons philosophy gives for this; for it seems to me that I immediately perceive external objects, and I take it that this is the ‘immediate relation’ that Hume is talking about.

(2) So far I don’t see anything that can be called an argument. Perhaps the passage was intended only for illustration. The argument—the only argument—is this:

The table that we see seems to shrink as we move away from it; but the real table that exists independently of us doesn’t alter; so what was present to the mind was not the real table but only an image of it. These are the obvious dictates of reason.

To judge the strength of this argument we must attend to the technical distinction between •real and •apparent size. The real size of a line is measured by some known measure of length, such as inches, feet, or miles. The real size of a surface or of a solid is measured by known measures of area or volume. This size is an object of touch only, and not of sight; and we couldn’t even have had any conception of it without the sense of touch, which is why Berkeley calls it ‘tangible size’.

Apparent size is measured by the angle that an object subtends at the eye. Suppose that two straight lines are drawn from the eye to the extremities of the object, making an angle at the eye: the apparent size ·of the object· is measured by this angle. It is an object of sight and not of touch; Berkeley calls it ‘visible size’.

The apparent size of the sun’s diameter is about 31 minutes of a degree.

The real size of the sun’s diameter is N thousand miles or K times the earth’s diameter.

This shows clearly that apparent size and real size are utterly different things, though each is called a ‘size’. The first is measured by an angle, the second by a line. The first pertains only to two dimensions (surfaces), the second to three dimensions (solids).

All this makes it obvious that the •real size of a body must continue unchanged while the body is unchanged. But is it also obvious that the •apparent size must stay the same while the body is unchanged? Far from it! Anyone who knows anything of mathematics can easily show that the same individual object, remaining in the same place and not altering, must vary in its apparent size according to the distance from which it is seen. . . . This is as certain as the principles of geometry.

There is also this point: Although the real size of a body is basically an object of touch, not of sight, we learn by experience to judge many real sizes by sight. We learn by experience to judge the approximate distance of a body from the eye, and from its distance and apparent size taken together we learn to judge its real size. And this kind of judgment, by being repeated every hour and almost every minute of our lives, eventually comes to us so easily and habitually that it greatly resembles the original perceptions of our senses, and can reasonably be called ‘learned perception’ ·as distinct from ‘original perception·’ [Reid often calls it ‘acquired perception’, evidently meaning the same as ‘learned perception’. This version will stay with ‘learned’ throughout, in the interests of clarity.]. . . . It is evident that by means of this we often discover by •one sense things that are properly and naturally the objects of •another. So I may correctly say ‘I hear a drum’ or ‘I hear a big bell’, though the shape or size of the sounding body is not originally an object of hearing. . . .

If these things are borne in mind, it will appear that Hume’s argument has no force to support his conclusion— indeed that it leads to the opposite conclusion. Here is the argument:

•The table we see seems to shrink as we move away from it—i.e. its apparent size lessens.

•The real table undergoes no alteration—i.e. there is no change in its real size.

Therefore

•What we see is not the real table.

I accept both the premises in this syllogism, but I deny the conclusion. The syllogism has two middle terms (as the logicians call them), ·whereas its validity requires there to be only one·. Apparent size is the middle term in the first premise, real size in the second. Therefore, according to the rules of logic, the conclusion is not validly inferred from the premises. Anyway, setting aside the rules of logic let us examine it by the light of common sense.

Suppose for a moment that it is the real table we see. Mustn’t this real table seem to shrink as we move away from it? It is demonstrable that it must. Well, then, how can this apparent shrinking be evidence that it is not the real table?. . . .

I remarked that Hume’s argument actually leads to the opposite opinion to his, i.e. leads to the conclusion that it is the real table that we see. The reason why is very plain: the •table we see has precisely the apparent size that the •real table must have when placed at that distance.

This argument is made much stronger by considering this:

The real table can be placed successively at a thousand different distances, and at every distance in a thousand different orientations; and its apparent size and apparent shape in each of those ·one million· distances and orientations can be determined demonstratively by the rules of geometry and perspective. Give the table, successively, as many of those different distances and orientations as you will—or all of them!—and for each of them open your eyes and look. You’ll see a table with precisely the apparent size and apparent shape that the real table must have at that distance and with that orientation.

Isn’t this a strong argument that it is the real table you see?

In short, the appearance of a visible object is infinitely diversified according to its distance and orientation. The visible appearances are innumerable for any one object, and when many objects are involved the number of different appearances is multiplied accordingly. Clever men have been theorizing about those appearances at least since the time of Euclid. They have accounted for all this variety on the supposition that the objects we see are external and not in the mind itself. The rules they have demonstrated about

•the various projections of the sphere,

•the appearances of the planets when they seem to go forward, to stop, and to go backwards, and

•all the rules of perspective

are built on the supposition that the objects of sight are external. Each rule can be tried in thousands of instances. In many arts and professions, innumerable trials are made every day, and they have never been found to fail in a single instance. Shall we say that a false supposition invented by the rough and primitive vulgar has had that much luck in explaining an infinite number of phenomena of Nature? This would surely be a greater feat than philosophy ever put on! And don’t forget that on the supposition that the objects of sight are internal—·are in the mind, not in the external world·—no account can be given of any one of those appearances. . . .

Now I have considered every argument I have found advanced to prove the existence of ideas or images of external things in the mind. If no better arguments can be found, I can’t help thinking that the whole history of philosophy has never provided another instance of an opinion so unanimously accepted by philosophers on such slight grounds.

(3) Although philosophers are unanimous as to the existence of ideas, they don’t agree much about anything else concerning them. If ideas weren’t a mere fiction, we’d be better placed to know about them than about anything else; yet there is nothing about which men differ so much.

Some have held them to be •self-existent, others to be •in God’s mind, others •in our own minds, and others again •in the brain or sensorium. . . .

Some philosophers insist that our ideas—or some of them—are innate, others that they are all caused from outside ourselves. Some derive them from the senses alone, others from sensation and reflection. As for how they are made, there are adherents of the views that

•they are manufactured by the mind itself,

•they are produced by external objects,

•they come from the immediate operation of God,

•impressions cause ideas, and we don’t know what causes impressions.

Some think that we have ideas only of material objects, but none of minds, of their operations, or of the relations of things; others think that the immediate object of every thought is an idea. Some think we have abstract ideas, and that this is what chiefly marks us off from the brutes; others maintain that there can’t be any such thing as an abstract idea. For some philosophers ideas are the immediate objects of thought, while for others they are the only objects of thought.

(4) Ideas were first invented, probably, as an aid to helping us understand some of the operations of the mind. Well, they don’t!

We are at a loss to know how we perceive distant objects, how we remember past things, how we imagine things that don’t exist. Ideas in the mind—·ideas that represent distant things, past things, non-existent things·—seem to account for all these operations, by reducing them all to a single operation. The operation is a kind of feeling or immediate perception of things that are present and in contact with the percipient; and feeling is an operation so familiar that we think it doesn’t need explanation but can help to explain other operations.

But this feeling or immediate perception is as hard to understand as the things it is said to explain. Two things can be in contact without any feeling or perception; so ·when there is some feeling or perception, there must be more than mere contact·—the percipient must have a power to feel or to perceive. How this power is produced, and how it operates, is quite beyond the reach of our knowledge. Nor can we know whether this power must be limited to things that are present and in contact with us. No-one can claim to prove that God, who gave us the power to perceive things that are present to us, may not give us the power also to perceive things that are distant, to remember things past, and to conceive things that never existed. . . .

(5) Finally, the natural and necessary consequences of this theory ·of ‘ideas’· rightly turn people against it—I mean people have a proper regard for the common sense of mankind.

It led the Pythagoreans and Plato to imagine that we see only the shadows of external things, and not the things themselves. It gave rise to the Aristotelian doctrine of ‘sensible species’, one of the greatest absurdities of that ancient system. And consider what has come of it since it was revived by Descartes. That great reformer in philosophy saw the absurdity of the doctrine about ideas •coming from external objects, and refuted it effectively after it had been accepted by philosophers for thousands of years; but he still retained ideas •in the brain and •in the mind. This is the foundation on which all our modern systems of the powers of the mind are based; and the tottering state of those structures, though they were built by skillful hands, can make us strongly suspect that the foundation is unsound.

It was this theory of ideas that led Descartes and his successors to think they needed philosophical arguments to prove the existence of material objects. Anyone can see that philosophy makes a fool of itself in the eyes of sensible men when it goes to work rounding up metaphysical arguments to prove that there is a sun and a moon, an earth and a sea! Yet we find these truly great men—Descartes, Malebranche, Arnauld, and Locke—seriously employing themselves in this argument. . . .

I might mention several paradoxes that Locke—no friend of paradoxes—was led into by this theory of ideas:

•The secondary ‘qualities of bodies’ are really just sensations of the mind.

•The primary qualities of body resemble our sensations.

•We have no notion of duration except from the succession of ideas in our minds.

•Personal identity consists in consciousness, so that the same individual thinking being can make several persons, and several thinking beings can make one person.

•Judgment is nothing but a perception of the agreement or disagreement of our ideas.

I shall examine most of these paradoxes when their turn comes.

Even these consequences of the doctrine of ideas were tolerable compared with the ones that were discovered later by Berkeley and Hume:

•There is no material world.

•There are no abstract ideas or notions.

•The mind is only a sequence of related impressions and ideas, without any thing that has them.

•There is no space or time.

•There is no body or mind—only impressions and ideas.

And the bottom line:

•There is no probability, even in demonstration itself, and no one proposition is more probable than its contrary.

These are the noble fruits that have grown on this theory of ideas since it began to be cultivated by skillful hands. It’s no wonder that sensible men should be disgusted with philosophy, when such wild and shocking paradoxes pass under its name. However, just because these paradoxes have been inferred from the theory of ideas with great acuteness and ingenuity and by valid reasoning, they must at last bring this advantage: Positions so shocking to the common sense of mankind, and so contrary to the decisions of all our intellectual powers, will open men’s eyes and break the force of the prejudice which has held them entangled in that theory.

Chapter 15: Leibniz’s system

There is one more theory of perception of which I shall give some account because of the fame of its author. It is the invention of the famous German philosopher Leibniz who, while he lived, held the first rank among the Germans in all parts of philosophy as well as in mathematics, in jurisprudence, in the knowledge of antiquities, and in every branch both of science and of literature. [Leibniz died about 70 years before this work appeared.]. . . . The famous controversy between him and the British mathematicians about whether he or Newton was the inventor of. . . .the differential calculus engaged the attention of mathematicians in Europe for several years. He also had a controversy with the learned and judicious Samuel Clarke about several points in the Newtonian philosophy that he disapproved of.

[Reid then sketches the main lines of Leibniz’s metaphysics, focussing on his view that x’s perceiving y is an upshot of a universe-wide ‘harmony’ in which every state of every simple substance is reflected or echoed in the states of every other. Reid impatiently rejects this in its entirety, objecting with special fierceness to Leibniz’s view that every state of any simple substance is a perception. Thus:] As consciousness is the only power by which we discern the operations of our own minds, or can form any notion of them, an operation of our mind of which we are not conscious is—who knows what? To call such an operation a ‘perception’ is a misuse of language. No-one can perceive an object without being conscious that he perceives it. No man can think without being conscious that he thinks. So anything that men are not conscious of can’t properly be called either perception or thought of any kind.

[The rest of Reid’s attack on Leibniz is not very instructive, but its closing paragraphs should be noted. Thus:]

My final remark about this system—and about all the others as well—is that it is all hypothesis, made up of unproved conjectures and suppositions. •The Aristotelians supposed that ‘sensible species’ are sent out by the objects of sense. •The moderns suppose that there are ideas in the brain or in the mind. •Malebranche supposed that we perceive the ideas of God’s mind. •Leibniz supposed monads and a pre-established harmony; and because these monads are creatures of his own making, he is free to give them whatever properties and powers his imagination may suggest. Similarly, the Indian philosopher supposed that the earth is supported by a huge elephant and that the elephant stands on the back of a huge tortoise (Locke, Essay II.xxiii.2).

Such suppositions, when no proof of them is offered, are nothing but fictions of the human fancy, and we oughtn’t to believe them any more than we believe Homer’s fictions concerning Apollo’s silver bow or Minerva’s shield or Venus’s girdle! In poetry such fictions are agreeable to the rules of the art. They are intended to please, not to convince. But the philosophers want us to believe their fictions. . . .

Men begin to have a true taste in philosophy only when they learn to regard hypotheses as negligible, and to consider them as theorizers’ day-dreams that will never have any similarity to the works of God.

God has given us some information about his works through •what our senses inform us concerning external things and •what our consciousness and reflection inform us concerning the operations of our own minds. Whatever can be validly and soberly inferred from these ordinary informations is true and legitimate philosophy. But anything that we add to this from conjecture is all spurious and illegitimate.

After this long account of the theories that philosophers have put forward to account for our perception of external objects, I hope you now see that. . . .none of those theories gives a satisfying account of this power of the mind or makes it more intelligible than it is without their aid. . . . Perception, consciousness, memory, and imagination are all basic simple powers of the mind, built into its constitution. That is why, though I have tried to show that the theories of philosophers on this subject are ill-grounded and insufficient, I don’t try to replace them by some other theory.

Everyone feels that perception gives him an unconquerable belief in the existence of the things he perceives, and that this belief is not the effect of reasoning, but the immediate consequence of perception. When philosophers have wearied themselves and their readers with their speculations on this subject, they can’t strengthen this belief or weaken it; nor can they show how it is produced. The belief puts the philosopher on a level with the peasant: neither of them can give any reason for believing his senses except that he finds it impossible not to.

Chapter 16: Sensation

Having said what I wanted to regarding the act of mind that we call ‘perception of an external object’, I proceed to consider another act of the mind which our make-up links with perception and indeed with many other mental acts. I refer to sensation. See my explanation of the word ‘sensation’ in Essay 1, chapter 1 [item 12].

Almost all our •perceptions have corresponding •sensations that constantly accompany them, and that fact makes us very apt to confuse the two. And we shouldn’t expect the sensation and its corresponding perception to be distinguished in ordinary language, because the purposes of everyday life don’t require it. . . . A •perceived quality and the •sensation corresponding to that perception often go under the same name.

This makes the names of most of our sensations ambiguous, which has created tangles and difficulties for philosophers. I’ll have to give some examples to illustrate the distinction between our sensations and the objects of perception.

When I smell a rose, this involves both sensation and perception. The pleasant odour I feel, considered by itself and not in relation to any external object, is merely a sensation. It affects the mind in a certain way, and this state of the mind can be conceived without any thought of the rose or of any other object. This sensation can’t be other than it is felt to be. Its very essence consists in being felt, and when it isn’t felt it doesn’t exist. There is no difference between •the sensation and •the feeling of it—they are one and the same thing. That is why I remarked earlier [Essay 1, chapter 1, item 12] that in sensation there is no •object distinct from •the act of the mind by which it is felt; and this holds true with regard to all sensations.

Now let us attend to the perception that we have in smelling a rose. Perception always has an external object, and in our present case the object of my perception is the quality in the rose that I detect by the sense of smell. Observing that the pleasant sensation occurs when the rose is near and stops when it is removed, I am led by my nature to conclude that some quality in the rose is the cause of this sensation. This quality in the rose is the object I perceive; and the act of my mind by which I have the conviction and belief in this quality is what in this case I call ‘perception’.

Notice, though, that •the sensation I feel and •the quality in the rose which I perceive are both called by the same name—‘the smell of a rose’. So this phrase has two meanings; and distinguishing them removes all the tangles, and enables us to give clear and distinct answers to questions about which philosophers have held much dispute.

For example, ‘Is the smell •in the rose or •in the mind that feels it?’ The answer is obvious; ‘the smell ·of the rose·’ can stand for either of two different things, one of which is •in the mind and can’t exist except in a sentient being, while the other is truly and properly •in the rose. The sensation that I feel is in my mind, and neither it nor anything like it could be in the rose, because the rose is not sentient. But this sensation in my mind is occasioned by a certain quality in the rose; the quality has the same name as the sensation, not because they are alike (which they aren’t) but because they constantly go together.

The names we have for smells, tastes, sounds, and the various degrees of heat and cold are all ambiguous in the same way; and what I have said about ‘the smell of a rose’ can be applied to them too. They signify both a •sensation and a •quality perceived by means of that sensation—a •sign and •something that is signified. Because they are conjoined by Nature, and the purposes of daily life don’t require them to be separated in our thoughts, they are both called by the same name. And this ambiguity occurs in all languages because the reason for it extends to all.

The same ambiguity is found in the names of diseases that are indicated by a particular painful sensation, such as ‘toothache’, ‘headache’. ‘Toothache’ signifies a painful sensation that can only exist in a sentient being; but it also signifies a disorder in the body, which is in no way similar to the sensation but is naturally connected with it.

Pressing my hand with force against the table, I •feel pain and I •feel the table to be hard. The pain is a sensation of the mind, and there’s nothing like it in the table. The hardness is in the table, and there’s nothing like it in the mind. We say that I ‘feel’ both, but that involves two senses of ‘feel’—a word that is applied to the •act of sensation and to the •act of perceiving by the sense of touch.

I touch the table gently with my hand, and I feel it to be smooth, hard, and cold. These are qualities of the table that I perceive by touch; but I perceive them by means of a sensation that indicates them. Because this sensation is not painful, I usually pay no attention to it. It carries my thought immediately to the thing signified by it, and is itself forgotten as though it had never existed. But by repeating it, turning my attention to it, and abstracting my thought from the thing signified by it, I find it to be merely a sensation, with no similarity to what it signifies—the hardness, smoothness, and coldness of the table.

It is difficult at first to attend separately to things that have always come as a pair, and to reflect on something for the very first time; but making the effort and putting in the practice will enable you overcome this difficulty, if you are one of those who have acquired the habit of reflecting on the operations of their own minds.

There are many mental operations to which we give one name, and think of as one thing, though they are really complex in their nature and made up of several simpler ingredients—sensation often being one of the ingredients. I shall give some instances of this. This takes us outside the over-all topic of this chapter, which requires us only to consider sensations that we have through our external senses. But this extension of our range will serve to illustrate things I have been saying, and I also think it is of importance in itself.

The appetite of hunger includes •an unpleasant sensation and •a desire of food. Sensation and desire are different acts of mind; desire must have an object, whereas sensation has no object. These two ingredients can always be thought about separately; perhaps sometimes one of them occurs without the other; but the term ‘hunger’ covers both.

Benevolence towards our fellow-creatures includes •a pleasant feeling and also •a desire for the happiness of others. The ancients commonly called benevolence a ‘desire’. Many moderns choose rather to call it a ‘feeling’. Both are right; and if there’s any error here it is the error of those who select one ingredient and exclude the other. Are these two ingredients necessarily connected? That may be hard for us to determine, because there are many necessary connections that we don’t perceive to be necessary; but ·even if they are necessarily linked·, we can separate them in thought. They are different acts of the mind.

•An unpleasant feeling and •a desire are in the same way ingredients of malevolent states such as malice, envy, revenge. Fear includes an unpleasant sensation or feeling and a belief that one is in danger; and hope is made up of the opposite ingredients. When we hear of a heroic action, it causes in our mind something made up of various ingredients—a pleasant feeling, a benevolent affection towards the person, and a judgment or opinion about his merit.

If we analyse the various operations of our minds in this way, we’ll find •that many of them that we think of as perfectly simple because we have been accustomed to call them by one name are made up out of simpler ingredients, and •that sensation (or feeling, which is only a more refined kind of sensation) is one of the ingredients not only in the perception of external objects but in most operations of the mind.

[We are about to encounter the word ‘sentiment’. In Reid it usually means ‘view’ or ‘opinion’, and up to here has been translated thus in the present text; but it can also mean ‘feeling’; in the present context the word is left alone in all its ambiguity, for the obvious reason.] A very little reflection can show us that the number and variety of our sensations and feelings is enormous. Our moral sentiments and sentiments of taste, and even our external senses, provide a great variety of sensations of different •kinds and, within almost every kind, an endless variety of •degrees. (Not to mention all the sensations that accompany our appetites, emotions, and affections.) Every discrimination that we make with regard to taste, smell, sound, colour, heat, cold, and the tangible qualities of bodies is indicated by a sensation corresponding to it.

The most general and most important classification of our sensations and feelings is into •pleasant, •unpleasant, and •neutral. Everything we call pleasure, happiness, or enjoyment (on the one hand) and everything we call misery, pain, or unpleasure (on the other) is a sensation or feeling. For no-one can be happier or more miserable at a given time than he then feels himself to be. He can’t be deceived about the enjoyment or suffering of that moment.

But I realize that besides the sensations that are either pleasant or unpleasant there are many more that are neutral. We attend so little to these that they have no name, and are immediately forgotten as if they had never existed. To be convinced of their existence we have to attend to the operations of our minds.

[Then a paragraph giving examples of such neutral sensations, and reasons for thinking there are countlessly many of them. Then:]

Neutral sensations are by no means useless. They serve as signs to distinguish things that are unalike, and the information we get concerning external things comes through them. Thus, for someone who wasn’t able to get •pleasure from the harmony or melody of sounds, ·or to get •unpleasure from noises of any sort·, the sense of hearing would still be extremely useful. . . . And the same thing holds for the sensations we have by all the other senses.

Sensations and feelings that are pleasant or unpleasant differ greatly not only in •degree but also in •kind and in •dignity. Some belong to the animal part of our nature, and we share them with the brutes—they are more properly called ‘sensations’. Others belong to our rational and moral part, and are more properly called ‘feelings’.

The intention of Nature in them is mostly obvious and well worth attending to. . . . In his distribution of pleasant and painful feelings, God has wisely and benevolently aimed at the good of the human species, and has even shown us by the same means how we ought to behave. •Painful sensations of the animal kind are warnings to avoid what would hurt us; and pleasant sensations of that same kind encourage us to act in ways that are required to preserve the individual or the species. •By the same means, Nature invites us to engage in moderate bodily exercise—telling us to avoid idleness and inactivity on the one hand, and excessive labour and fatigue on the other. •The moderate exercise of all our rational powers gives pleasure. •Every species of beauty is beheld with pleasure, and every species of ugliness with disgust; and we shall find that everything we find beautiful is either admirable or useful in itself or a sign of something that is admirable or useful. •The benevolent affections are all accompanied by a pleasant feeling, and the malevolent ·attitudes· with an unpleasant one. •The highest, noblest, and most durable pleasure is that of doing well and acting as we should; and the most bitter and painful sentiment is the anguish and remorse of a guilty conscience. . . .

I shall end this chapter by remarking that just as

confusing our sensations with the perception of external objects that is constantly conjoined with them has given rise to most of the errors and false theories of philosophers concerning the senses,

so also

distinguishing these operations seems to me to be the key that leads to a right understanding of both ·sensations and perceptions·.

‘Sensation’ doesn’t in itself imply a conception of or belief in any external object. It implies a sentient being, and a certain way in which that being is affected, and that is all it implies. ‘Perception’ implies an immediate conviction and belief in something external—something different both from the mind that perceives and from the act of perception. Things that are intrinsically as different ·as perception and sensation are· ought to be distinguished; but we are so built that in us they are always united. Every perception comes along with its own special kind of sensation. The sensation is the sign, the perception is the thing signified. They coalesce in our imagination. They are given a single name, and are thought of as one simple operation. The purposes of everyday life don’t require them to be distinguished.

The philosopher—and he alone—does have reason to distinguish them when he wants to analyse the compound operation that they make up. But he has no suspicion that there is anything compound here, and to learn that there is requires a degree of reflection that has been too little practised, even by philosophers.

In the ancient philosophy, sensation and perception were completely run together. A ‘sensible species’ coming from the object and impressed on the mind was the whole ·story·—and you could call it ‘sensation’ or ‘perception’ as you pleased.

Descartes and Locke, paying more attention to the operations of their own minds, say that the sensations that tell us of secondary qualities are not like anything that pertains to body; but they didn’t see that this can just as well be said about primary qualities. Locke maintains that the sensations we have from primary qualities are like those qualities. This shows how grossly the cleverest men can go wrong with regard to the operations of their minds. I don’t deny that it is much easier to have a clear notion of the sensations belonging to secondary qualities than of those belonging to primary qualities; I’ll explain why this is so, early in the next chapter.

But if Locke had attended carefully enough to the sensations that he was receiving from primary qualities every day and every hour, he would have seen that they can’t resemble any quality of an inanimate thing, any more than pain can resemble a cube or a circle.

Berkeley saw clearly the thing that the able Locke had missed. He had a correct notion of •sensations, and saw that no quality of an insentient thing could possibly resemble •them—a truth that is so evident in itself that it is amazing that it was for so long unknown.

Let us attend now to the consequence of this discovery. Philosophers as well as the vulgar had been accustomed to giving one name to sensation and perception, and to regard them as a single simple operation. Philosophers, even more than the vulgar, gave the name ‘sensation’ to the whole operation of the senses, and all the notions we have of material things were called ‘ideas of sensation’. This led Berkeley to take one ingredient of a complex operation to be the whole operation; and having clearly discovered the nature of sensation, and taking it for granted that the senses present to the mind only sensation, which can’t resemble anything material, he concluded that there is no material world.

If the senses provided us with no materials of thought except sensations, his conclusion would be right; for no sensation can give us the conception of material things, let alone any argument to prove their existence. But if in fact our senses give us not only a variety of •sensations but also a •conception of external objects and an immediate natural •conviction that they exist, he reasons from a false supposition and his arguments fall to the ground.

Chapter 17: Objects of perception, starting with primary and secondary qualities

The objects of perception are the various qualities of bodies. Intending to treat of these only in general, and chiefly with a view to explain the notions which our senses give us of them, I begin with the distinction between primary and secondary qualities. These were distinguished very early. The Aristotelian system confounded them and left no difference. The distinction was revived by Descartes and Locke, and a second time abolished by Berkeley and Hume. If the real foundation of this distinction can be pointed out, that will enable us to account for the various revolutions in the sentiments of philosophers concerning it.

Everyone knows that Locke gave the name ‘primary qualities’ to extension, divisibility, shape, motion, solidity, hardness, softness, and fluidity; and that he called sound, colour, taste, smell, and heat or cold ‘secondary qualities’. Is there a sound basis for this distinction? Is there anything that is true of all the ‘primary’ qualities and none of the ‘secondary’ ones? And what is it?

I answer that there seems to me to be a real basis for the distinction; namely this:

•Our senses give us a direct and distinct notion of the primary qualities, and inform us what they are in themselves.

•But our senses give us only a relative and obscure notion of the ‘secondary’ qualities. They inform us only that they are qualities that affect us in a certain way, i.e. produce in us a certain sensation; but our senses tell us nothing about what the secondary qualities are in themselves.

Any thinking person can easily satisfy himself that he has a perfectly clear and distinct notion of extension, divisibility, shape, and motion. A body’s solidity means merely that it prevents other bodies from occupying the place it is in while it is there. Hardness, softness, and fluidity are different degrees of cohesion in the parts of a body: the body is fluid when it has no detectable cohesion, soft when its cohesion is weak, and hard when it is strong. We don’t know what causes this cohesion, but we do understand the cohesion itself, being immediately informed of it by the sense of touch. . . .

And, as I noted, our notion of primary qualities is direct, not merely relative. A relative notion of a thing is strictly speaking not a notion of the thing at all, but only of some relation which it bears to something else.

Thus ‘gravity’ sometimes signifies the •tendency of bodies ·to move· towards the earth, and sometimes signifies the •cause of that tendency. When it means the •tendency, I have a direct and distinct notion of gravity—I see it and feel it and know perfectly what it is. But this tendency must have a •cause. We call the cause ‘gravity’ too, and people have thought and theorized about what it is. Now, when we think and reason about this cause, what notion of it do we have? Obviously, we think of it as an unknown cause of a known effect. This is a relative notion, and it is bound to be obscure because it gives us no conception of what the thing is but only of what relation it has to something else. . . . There are many objects of thought and of discourse of which our faculties can give us no better than a relative notion.

That explanation makes it clear that our notion of primary qualities is not of this relative kind. We know what the primary qualities are, not merely how they relate to something else.

It is otherwise with secondary qualities. ‘What is that quality or state of a rose that you call its smell?’ I am at a loss to answer directly. On reflection I find that I do have a distinct notion of the sensation that the quality in question produces in my mind; but there can’t be anything like this sensation in the rose, because it is not sentient. What that quality is I don’t know. . . . And the same line of thought applies to every secondary quality.

Thus I think it appears that there is a real basis for distinguishing primary from secondary qualities. The account I have given of this distinction isn’t founded on any hypothesis. That our notions of primary qualities are direct and distinct, while those of the secondary qualities are relative and obscure, are matters of fact that you can know for sure by attentively reflecting on them. Here, now, are some thoughts on this subject.

1. The primary qualities are not sensations or like sensations. This strikes me as self-evident. I have a clear and distinct notion of each of the primary qualities. I have a clear and distinct notion of sensation. When I hold them together in my mind I can’t detect any resemblance. Sensation is the act or the feeling (never mind which) of a sentient being. Shape, divisibility, solidity are not acts or feelings. A sensation must be had by a sentient being, for ‘a sensation that is not felt by some sentient being’ is an absurdity. Shape and divisibility must be had by something that is shaped and divisible, but not by something sentient.

2. We have no reason to think that any of the secondary qualities resemble any sensation. The absurdity of this notion has been clearly shown by Descartes, Locke, and many modern philosophers. It was a tenet of the ancient philosophy, and many ·philosophers· attribute it to the vulgar even today, but only as a vulgar error. That the vibrations of a bell don’t resemble the sensation of sound, and that the little particles emanating from a piece of cheese don’t resemble the sensation of smell—these truths are too obvious to need proof.

3. The distinctness of our notions of primary qualities prevents all questions and disputes about their nature. There are no differences of opinion about the nature of extension, shape, or motion, or about the nature of any ·other· primary quality. Their nature is manifest to our senses, and no-one can be ignorant of them or mistaken about them, though their causes may admit of dispute.

The primary qualities are treated in the mathematical sciences, and the distinctness of our notions of them enables us to reason demonstratively about them to a great extent. Their various modifications [= ‘special cases’, e.g. circularity is a modification of shape] are precisely defined in the imagination, which enables us to compare them and establish their relations with precision and certainty.

It is not so with secondary qualities. . . . Our feeling informs us that the fire is hot, but it doesn’t tell us what that heat of the fire is. ‘Isn’t it a contradiction to say we •know that the fire is hot but •don’t know what that heat is?’ I answer that there is the same appearance of contradiction in many things that are certainly true. We •know that wine has an inebriating quality; but we •don’t know what that quality is. Of course, if we didn’t have any notion of what is meant by ‘the heat of fire’ or by ‘an inebriating quality’, we couldn’t meaningfully affirm anything of either of them. But we do have a notion of each, but it is only a relative notion. We know that they are the causes of certain known effects.

4. The nature of secondary qualities is a proper subject of philosophical inquiry, and philosophy has made some progress on this topic. It has been discovered that

•the sensation of smell is occasioned by particles emitted by bodies,

•the sensation of sound is occasioned by bodies’ vibration, and that

•the sensation of colour is occasioned by bodies’ disposition to reflect a particular kind of light.

Interesting and surprising discoveries have been made concerning the nature of heat, and a rich field of ·further· discovery about these subjects lies open.

5. We can see why our attention is drawn to the sensations belonging to secondary qualities but not to the sensations that belong to the primary qualities.

[Reid in this next paragraph writes a little confusingly, referring to a secondary quality as ‘the object’. This will be avoided by expressing his point in terms of a single secondary quality, namely heat.] The sensation belonging to the secondary quality heat is not only a sign of heat—it forms a large part of the notion we have of heat. We think of heat only as what occasions such and such a sensation, so we can’t think about it without thinking of the sensation that it occasions. We have no other mark by which to distinguish it. ·Generalizing now·, the thought of any secondary quality always carries us back to the sensation that it produces; we give the same name to both, and are apt to run them together.

But having a clear and distinct conception of primary qualities, we can think of them without recalling their sensations. When a primary quality is perceived, the sensation immediately leads our thought to the quality signified by it, and is itself forgotten. We have no reason afterwards to reflect on it, and so we come to be as little acquainted with it as if we had never felt it. Nature intended the sensations belonging to primary qualities only as signs; and when they have served that purpose they vanish.

The only exception is when the sensations are so painful or so pleasant as to draw our attention. When a man bangs his hand against a pointed hard body, he feels pain, and can easily believe that this pain is a sensation and that there is nothing resembling it in the hard body; at the same time he perceives the body to be hard and pointed, and he knows that these qualities belong to the body only. In this case it is easy to distinguish •what he feels from •what he perceives—·i.e. to distinguish •his pain from •the body’s hardness and pointedness·. . . .

·THE VULGAR VERSUS THE PHILOSOPHERS·

We are now to consider the opinions both of the vulgar and of philosophers on this subject. It is not to be expected that the vulgar should make distinctions that have no connection with ordinary everyday life, which is why they don’t distinguish primary qualities from secondary ones, but speak of both as being equally qualities of the external object. They have a distinct notion of the primary qualities, because these are immediately and distinctly perceived by the senses. Their notions of the secondary qualities are ·less satisfactory, but they· aren’t erroneous, merely confused and indistinct. A secondary quality is the unknown cause or occasion of a well known effect, and the cause and the effect are given the same name. Now, sharply distinguishing •the different ingredients of a complex notion and, at the same time, •the different meanings of an ambiguous word, is the work of a philosopher; and we can’t expect the vulgar to do it when they have no practical need to.

. . . .There seems to be a contradiction between the vulgar and the philosopher on this subject, and each accuses the other of a gross absurdity. The vulgar say: ‘Fire is hot, snow is cold, sugar is sweet; and to deny this is a gross absurdity that contradicts the testimony of our senses.’ The philosopher says: ‘Heat and cold and sweetness are nothing but sensations in our minds; and it is absurd to think of these sensations as being in the fire, the snow, or the sugar.’

I think that this contradiction between the vulgar and the philosopher is more apparent than real; and that it arises from a misuse of language on the part of the philosopher and from unclear notions on the part of the vulgar. The philosopher says ‘There is no heat in the fire’, meaning that the fire doesn’t have the sensation of heat. What he means is right, and the vulgar will agree with him as soon as they understand what he means. But his language is improper; for there really is a quality in the fire of which the proper name is ‘heat’; and this name ‘heat’ is given to this quality—both by philosophers and by the vulgar—much more frequently than to the sensation of heat. . . .

·HISTORY OF VIEWS ABOUT THE DISTINCTION·

As I have already remarked, there have been different phases in the opinions of philosophers about primary and secondary qualities. They were distinguished long before Aristotle’s time by the atomists, among whom Democritus looms large. Back then the name ‘quality’ was applied only to the ones we call ‘secondary’ qualities, because primary qualities being considered as essential to matter, and were not called ‘qualities’. Those philosophers had no doubt that the atoms that they held to be the basic sources of things were extended, solid, shaped, and movable, but there was a question as to whether they had •smell, taste, and colour (or, in the terminology they used, whether they had •qualities.) The atomists maintained that they didn’t, and that the qualities were not in bodies but were an effect of the action of bodies on our senses.

It would seem that when men began to think about this subject the primary qualities appeared so clear and obvious that the thinkers couldn’t doubt that they existed wherever matter existed; but the secondary were so obscure that they didn’t know where to locate them. They used this comparison: as •fire is produced by the collision of •flint with •steel without being in either of them, so also •the secondary qualities are produced by the impact of •bodies on •our senses without being in either of them.

Aristotle disagreed. He thought that taste and colour are substantial forms of bodies, and that their ‘species’ as well as those of shape and motion are received by the senses. [Reid has explained ‘substantial form’ here, and the present sense of ‘species’ = ‘sensible species’ in Essay 1, chapter 1, middle of item 10.]

In believing that what we ordinarily call ‘taste’ and ‘colour’ is something really inherent in body, and doesn’t depend on its being tasted or seen, Aristotle followed •Nature. But in believing that our sensations of taste and colour are the ‘forms’ or ‘species’ of those qualities, received by the senses, he followed •his own theory which was an absurd fiction. Descartes not only showed the absurdity of ‘sensible species received by the senses’ but gave a sounder and more intelligible account of secondary qualities than had been given before. Locke followed him, and took a lot of trouble with this subject. I think it was he who first called them ‘secondary qualities’, a name that has been very generally adopted. He distinguished •the sensation from •the quality in the body which is the cause or occasion of that sensation, and showed that there isn’t and can’t be any similarity between them.

This account clears the senses of the charge of lying to us: the sensation is real, with nothing erroneous about it; the quality in the body that causes or occasions this sensation is also real, though its nature isn’t manifest to our senses. If we deceive ourselves by confusing the sensation with the quality that occasions it, this comes from rash judgment or weak understanding, not from false testimony of our senses. I regard this account of secondary qualities as very sound; and if Locke had stopped here, he would have left the matter very clear. But he thought he had to introduce the theory of ideas to explain the distinction between primary and secondary qualities, and by that means I think he tangled and darkened it.

When philosophers speak about ‘ideas’, we’re often at a loss to know what they mean by that word, and may well suspect that ideas are mere fictions. The philosophers have told us that by ‘the ideas that we have immediately from our senses’ they mean our sensations. These are indeed real things, not fictions. By attending to them carefully we can completely know their nature; and if philosophers kept to this meaning of ‘idea’ when applied to the objects of sense they would at least be more intelligible. Let us hear how Locke explains the nature of those ideas when applied to primary and secondary qualities:

To reveal the nature of our ideas better, and to talk about them intelligibly, it will be convenient to distinguish them •as they are ideas or perceptions in our minds, and •as they are states of matter in the bodies that cause such perceptions in us. That may save us from the belief (which is perhaps the common opinion) that the ideas are exactly the images and resemblances of something inherent in the object. ·That belief is quite wrong·. Most ideas of sensation are (in the mind) no more like a thing existing outside us than the names that stand for them are like the ideas themselves. (Essay II.viii.7)

This way of distinguishing a thing—first as what it is, then as what it is not—strikes me as a very extraordinary way of revealing its nature. If ideas are •‘ideas or perceptions in our minds’ and at the same time •‘the states of matter in the bodies that cause such perceptions in us’, it won’t be easy to talk about them intelligibly!

The account of the nature of ideas is carried on in Locke’s next section in an equally extraordinary manner:

Whatever the mind perceives in itself—whatever is the immediate object of perception, thought, or understanding—I call an idea; and the power to produce an idea in our mind I call a quality of the thing that has that power. Thus a snow-ball having the power to produce in us the ideas of white, cold, and round, the powers to produce those ideas in us, as they are in the snow-ball, I call qualities; and as they are sensations or perceptions in our understandings, I call them ideas. If I sometimes speak of ‘ideas’ as in the things themselves, please understand me to mean to be talking about the qualities in the objects that produce them in us. (II.viii.8)

These are the distinctions that Locke thought would help to ‘reveal the nature of our ideas’ of the qualities of matter better, so that we could ‘talk about them intelligibly’! I think it will be hard to find two other paragraphs in the Essay as unintelligible as these. Does this come from •the intractable nature of ideas or from •Locke’s drowsy inattention (a fault of which he is very rarely guilty)? Judge for yourself. Several other passages in that chapter are also obscure in the same way, but I shan’t dwell on them. Locke’s bottomline conclusion is that primary and secondary qualities are distinguished by this:

•The ideas of the primary qualities resemble or copy the qualities.

•The ideas of the secondary qualities do not resemble or copy the qualities.

There are two things I want to say about this doctrine.

(1) Taking it for granted that by the ‘ideas’ of primary and secondary qualities he means the sensations they arouse in us, I remark that it appears strange that a sensation should be the idea of a quality in body to which it is admitted to have no resemblance. If the •sensation of sound is the idea of the •vibration of the bell that occasions it, a •surfeit may for the same reason be the idea of a •feast!

(2) When Locke affirms that the ideas of primary qualities—i.e. the sensations they arouse in us—resemble those qualities, he seems not to have attended properly either to (a) those sensations or to (b) the nature of sensation in general.

(a) Press your hand against a hard body and attend to thesensation you feel, excluding from your thought everything external, even the body that is the cause of your feeling. This abstraction ·or exclusion· is indeed difficult, and it has hardly ever been done. But it is possible, and it is obviously the only way to understand the nature of the sensation. Properly attending to this sensation will satisfy you that •it is no more like •hardness in a body than the •sensation of sound is like •vibration in a bell.

The only ideas I know of are my conceptions. My ‘idea of hardness in a body’ ·in that sense· is the conception of

a body’s having parts that cohere [= ‘hold together’] so that a great deal of force is needed to pull them apart.

When I have a •sensation of pain from pressing my hand against a hard body, I have at the same time both the •conception of and the •belief in this quality in the body. My constitution conjoins the •sensation with the perception— ·and thus with the •conception and •belief involved in perception·—but I’m sure they are in no way alike. The only basis for calling one the ‘idea of’ the other would be an equally good or bad basis for calling every natural effect the ‘idea of’ its cause—·e.g. for calling an over-full stomach the ‘idea of’ the preceding feast·.

(b) When Locke said that the sensations aroused by primary qualities (which he called the ‘ideas of’ the primary qualities) resemble those qualities, he hadn’t attended adequately to the nature of sensation in general. The proposition

There can’t be anything like sensation in an insentient being, or anything like thought in an unthinking being

is self-evident, and Berkeley has shown that all thinking people accept it. Yet it was unknown to Locke! It is a humbling fact that in subjects of this kind self-evident truths can be hidden from the eyes of the ablest men. But we have consolation in the fact that when such truths are revealed they shine by their own light—light that can’t be extinguished again. . . .

Berkeley adopted the common philosophical view about the ideas we have by our senses, namely that they are all sensations; but then he saw more clearly ·than his predecessors had done· what follows from this doctrine, namely that there is no material world, and that there are no primary or secondary qualities and thus no basis for any distinction between them. He exposed the absurdity of the view that our sensations resemble any quality—primary or secondary—of a substance that is supposed to be insentient. Indeed, if you allow that the only role of the senses is to provide us with sensations, you’ll find it impossible to make any distinction between primary and secondary qualities, or even to maintain the existence of a material world.

From the account I have given of the various turns in the opinions of philosophers about primary and secondary qualities, I think it appears that all the darkness and complexity that thinking men have found in this subject, and the errors they have fallen into, have come from the difficulty of clearly distinguishing sensation from perception, what we feel from what we perceive.

[Then two paragraphs that repeat things that have already been said more than once in this Essay. Ending with:] The progress made in correctly analysing the operations of our senses has been very slow. The theory about ‘ideas’. . . .has greatly held back this progress; we might hope for a quicker advance if philosophers could humble themselves enough to believe that in every branch of the philosophy of Nature the productions of human fancy and conjecture will be found to be •dross; and that the only pure •metal that will stand up to testing is what is discovered by patient observation and properly conducted induction.

Chapter 18: Other objects of perception

Besides primary and secondary qualities of bodies there are many other immediate objects of perception. Without claiming to offer a complete list, I think they mostly belong to one or another of the following five classes:

(1) Certain states or conditions of our own bodies.

(2) Mechanical powers or forces.

(3) Chemical powers.

(4) Medical powers.

(5) Powers of plants and animals.

·I shall discuss the first two of these and sketchily allude to the other three·.

(1) No-one would deny that we perceive certain disorders in our own bodies by means of unpleasant sensations that Nature has attached to them. Of this kind are toothache, headache, gout, and every illness and physical injury that we feel. The notions that our senses give of these have a strong analogy to our notions of secondary qualities. The two kinds of notions are built up in the same way, and can be analysed along similar lines. Also, they throw light on one another.

In toothache, for instance, there is first a painful feeling and secondly a conception of and belief in something wrong in the tooth that is believed to be causing the unpleasant feeling. The first is a •sensation, and the second is •perception because it includes a conception of and belief in an external object. But although these two things are of different natures, they are so constantly conjoined in our experience and in our imagination that we think of them as one, and call them both ‘toothache’, which is the correct name both for the pain and for the disorder in the tooth that causes the pain. Is the toothache in the mind that feels it or in the tooth that has something wrong with it? A great deal could be said on each side of this question if it isn’t noticed that ‘toothache’ has two meanings. . . .

We say that we feel the toothache, not that we perceive it. On the other hand we say that we perceive the colour of a body, not that we feel it; yet in each of these there is sensation and perception conjoined. Can any reason be given for this difference of terminology? I answer Yes, the reason being this:

•In the toothache, the sensation is very painful and strongly calls attention to itself; and this leads us to speak of it as if it were only felt and not perceived.

•In seeing a coloured body, the sensation is neutral and doesn’t attract our attention. The quality in the body that we call its ‘colour’ is the only object of attention; and so we speak of it as if it were perceived and not felt.

Though all philosophers agree that seeing colours involves sensations, it isn’t easy to persuade the vulgar that when they see a coloured body in a moderate light and with a healthy eye they have any sensation or feeling at all.

Some sensations are very often felt yet never attended to or thought about. We have no conception of them, and so we have no name for them and no turns of phrase that imply their existence. Such are the sensations of colour, and of all primary qualities; and therefore those qualities are said to be perceived but not to be felt. Taste and smell and heat and cold have sensations that are often strongly pleasant enough, or strongly unpleasant enough, to draw our attention to them, and they are sometimes said to be ‘felt’ and sometimes to be ‘perceived’. . . .

[Then more than a page on issues related to ‘I feel a pain in my toe’. Reid insists that this can be a perfectly good thing to say; it can report a real fact, in language that is correct because universally accepted and understood. It is for the philosophers to analyse ‘pain in my toe’, and Reid shows how to do this. He deals similarly with the phenomenon of feeling a ‘phantom pain’ in a leg that has been amputated, and goes on to discuss supposed ‘deceptions of the senses’. In every such case, Reid says, the senses deliver a sensation which doesn’t imply anything and therefore can’t be deceptive; but there may be, associated with the sensation, a perception—a conception and belief—and this can be and sometimes is deceptive. Then:]

(2) Let us next consider the notions our senses give us of the attributes of bodies called ‘powers’. There’s a special need to look into this topic, because ‘power’ seems to imply some activity, yet we consider body as a dead inactive thing which doesn’t act but can be acted on.

Of the mechanical powers ascribed to bodies, let us start with the one called their vis inertia [= ‘power of not moving’]. This means merely that bodies never change their state themselves—whether starting to move, stopping moving, or changing speed or direction. Any such change must come from some force impressed on them ·from the outside·; and the change that is produced is exactly proportional to the strength and direction of that external force.

That all bodies have this property is a matter of fact that we learn from daily observation as well as from the most precise experiments. It seems clear that this ·property· doesn’t imply any activity in body, but rather the contrary. Activity in a body would be involved in its having a power to •change its state rather than its •continuing in the same state. So this property of bodies, despite its name, does not imply any ‘power’ properly so-called.

Now consider the power of gravity. It is a fact that all the bodies of our planetary system gravitate towards each other. This has been fully proved by the great Newton. But he doesn’t think of this gravitation as a power inherent in bodies, which they exercise of themselves; rather, he takes it to be a force imposed on them, to which they must necessarily yield. We don’t know whether this force is imposed on them by some superfine ether, or by the power of God or of some subordinate spiritual being; but all sound natural philosophy, especially Newton’s, takes it to be a force that is imposed on bodies and not inherent in them.

So when bodies gravitate they don’t strictly speaking act, but are acted on. They only succumb to an impression that is made on them. We ordinarily express by active verbs many changes in things in respect of which they are merely passive. And this way of speaking is used chiefly when the cause of the change is not obvious to the senses. Thus we say that a ship ‘sails’ when every man of common sense knows that it has no inherent power of motion and is only driven by wind and tide. Similarly, when we say that the planets ‘gravitate’ towards the sun, all we mean is that some unknown power pulls or pushes them in that direction.

What I have said about the power of gravitation can be re-applied to other mechanical powers such as cohesion, magnetism, electricity; and also to chemical and medical powers. By all these, certain effects are produced when one body is applied to another. Our senses discover the effect, but the power is hidden. We know there must be a cause of the effect, and we form a relative notion of it from its effect; and very often the same name is used to signify the unknown cause and the known effect.

We ascribe to plants the powers of drawing nourishment, growing, and multiplying their kind. Here too the effect is manifest but the cause is hidden from the senses. So these powers, like the others that we ascribe to bodies, are unknown causes of certain known effects. It is the business of philosophy to investigate the nature of those powers as far as we can, but our senses leave us in the dark. We can see a great similarity in the notions that our senses give us of

•secondary qualities,

•the disorders we feel in our own bodies, and

•the various powers of bodies that I have listed.

They are all obscure and relative notions—each being a conception of some unknown cause of a known effect. They mostly have a single name for the effect and for its cause; and they are a proper subject of philosophical discussion. It wouldn’t be wrong, I think, to call them occult qualities.

This label has indeed fallen into disgrace since the time of Descartes. The Aristotelians are said to have used it to cloak their ignorance and to stop all enquiry into the nature of the qualities they called ‘occult’. So be it. Let those who were guilty of this misuse of the word answer for their crime! To call a thing ‘occult’, if we attend to the meaning of the word, is not to cloak one’s ignorance but rather to own up to it modestly. It is to point the thing out as a proper subject for the investigation of philosophers, whose business it is to better the condition of humanity by discovering what was before hidden from human knowledge.

So if I were to offer a classification of the qualities of bodies in terms of how they appear to our senses, I would divide them first into •manifest and •occult. The manifest qualities are those that Locke calls ‘primary’—such as extension, shape, divisibility, motion, hardness, softness, fluidity. The nature of these is manifest even to our senses; and the business of the philosopher with regard to them is not •to find out their nature (because that is already well known) but •to discover the effects that are produced by their various combinations, and with regard to those of them that aren’t essential to matter •to discover their causes as far as he can.

The occult qualities can be subdivided into various kinds:

•the secondary qualities;

•the disorders we feel in our own bodies;

•the qualities we call ‘powers of bodies’, whether mechanical, chemical, medical, animal, or vegetable; and

•any others there may be that aren’t already covered.

The existence of these ·isn’t hidden; it· is manifest to our senses; but their nature is occult; and here the philosopher has an ample field ·of inquiry open before him·.

God in his generosity has made manifest to all men what we need for the conduct of our animal life. But there are many other precious secrets of Nature the discovery of which enlarges man’s power and raises his state. These are left to be discovered by the proper use of our rational powers. They are hidden not so that they’ll always be concealed from human knowledge, but so that we may be stimulated to search for them. This is the proper business of a philosopher, and it is the glory of a man and the best reward of his labour to discover what Nature has thus concealed. [Reminder: ‘philosopher’ here includes the meaning of ‘scientist’.]

Chapter 19: Matter and space

The objects of sense that we have considered up to here are qualities. But any quality must have a subject, ·i.e. some thing that has the quality·. We give the names ‘matter’, ‘material substance’ and ‘body’ to the subject of sensible qualities, and the question arises: What is this matter?

In a billiard ball I perceive shape, colour, and motion; but the ball is not shape, is not colour, is not motion, nor is it all three of these taken together; it is something that has shape and colour and motion. This is a dictate of Nature, and is what everyone believes.

As to the nature of this ‘something’, I’m afraid I can give little account of that except to say: It has the qualities that our senses discover.

‘How do we know that they are qualities, and that they can’t exist without a subject?’ I admit I can’t explain how we know that they can’t exist without a subject, any more than I can explain how we know that they exist. Nature tells us that they exist, and I think it also tells us that they are qualities.

The belief that shape, motion, and colour are qualities and require a subject must be either •a judgment of Nature, or •revealed by reason, or •a prejudice with no solid basis. Some philosophers maintain that it is a mere prejudice; that a body is nothing but a collection of what we call ‘sensible qualities’, and that they don’t have any subject and don’t need one. This is the opinion of Berkeley and Hume; and they were led to it by finding that they didn’t have in their minds any idea of substance. It couldn’t be an idea of sensation or of reflection.

But to me nothing seems more absurd than to suppose there is extension without anything extended, or motion without anything that moves; but I can’t give reasons for my opinion because it seems to me self-evident and an immediate dictate of my nature.

And it is also the belief of all mankind; this is shown by the structure of all languages, in which we find adjectives used to express sensible qualities. It is well known that every adjective in language must belong to some substantive expressed or understood; that is every quality must belong to some subject.

[Then two paragraphs developing the thesis that it is a ‘judgment of Nature’ that the things we immediately perceive are qualities that must be qualities of something. Then:]

In this ·intellectual area·, the philosopher seems to be no better placed than the vulgar. They perceive colour and shape and motion by their senses as well as he does, and they are as certain as he is that there is a subject of those qualities. Furthermore, the notions they have of this subject are no more obscure than his. When the philosopher calls it a ‘substratum’ and a ‘subject of inhesion’, those learned words mean only what every man understands and expresses by saying in common language that it’s an extended and solid and movable thing.

The relation that sensible qualities have to their subject—i.e. to the body that has them—is not so dark that it can’t be easily distinguished from all other relations. Everyone can distinguish it from the relation of effect to cause, of means to end, of a sign to the thing it signifies.

I think it requires some maturity of understanding to distinguish •the qualities of a body from •the body. It may be that brute animals and human infants don’t make this distinction; and if you think that this distinction is made not by our senses but by some other power of the mind, I shan’t dispute the point—as long as you grant me that men when their faculties are mature have a natural conviction that sensible qualities can’t exist by themselves without some subject to which they belong.

I do indeed think that some of the views about matter that we arrive at can’t be deduced solely from the testimony of sense, and must be assigned to some other source.

·DIVISIBILITY OF BODY·

It seems to be utterly evident that all bodies must consist of parts, and that every part of a body is itself a body—a distinct being that can exist without the other parts—and yet I don’t think this conclusion is deduced solely from the testimony of sense. For one thing: the divisibility of all body is a necessary truth, and therefore not something learnable from the senses. Also: there is a limit to how fine a division of a body we can perceive; eventually the parts become too small to be perceived by our senses; but we are still quite sure that the body could be further divided while still continuing to be a body. We carry on the division and subdivision in our thought, far beyond the reach of our senses, and we can find no end to it. I think indeed that we plainly discern [Reid’s word] that there can’t be any limit to how far the division can be carried. ·Here is an argument for this conclusion·. If there is a limit to this division, then either division can bring us to

•a body that is extended but has no parts and is absolutely indivisible,

or it can bring us to

•a body that is divisible but will stop being a body the moment it is divided.

Both of these positions seem to me absurd, yet the truth of one or the other of them is the necessary consequence of supposing a limit to the divisibility of matter.

On the other hand, if it is admitted that the divisibility of matter has no limit, it will follow that no body can be called one individual substance. You may as well call it two or twenty or two hundred. For when it is divided into parts, every part is a being or substance distinct from all the other parts, and was so even before the division. Any one part could continue to exist even if all the other parts were annihilated.

There is indeed a principle, long accepted as an axiom in metaphysics, which I can’t reconcile with the ·endless· divisibility of matter. It is the principle:

Every being is one—omne ens est unum [Latin].

I take this to mean that every thing that exists must either be one indivisible being or be composed of a determinate number of indivisible beings. Thus an army can be divided into regiments, a regiment into companies. and a company into men. But here the division has its limit, for you can’t divide a man without destroying him, because he is an individual; and according to this axiom everything must be an individual or be made up of individuals.

There can be no doubt that this axiom holds with regard to an army, and with regard to many other things. But what evidence is there that it holds for all beings whatsoever?

Leibniz, conceiving that all beings must have this metaphysical unity, was led to maintain that matter and indeed the whole universe is made up of ‘monads’, i.e. •simple and indivisible substances.

It may have been the same line of thought that led Boscovich into his hypothesis, which seems to me much more ingenious than Leibniz’s, namely that matter is composed of a definite number of •mathematical points that are endowed with certain powers of attraction and repulsion.

The divisibility of matter without any limit seems to me more tenable than either of these hypotheses. As for the metaphysical axiom ·about unity that led to them·: I don’t attach much weight to that, considering its origin. Metaphysicians thought they should develop a science devoted to the attributes that are common to all beings. It must be pretty hard to find out such attributes! After racking their brains, they specified three—unity, truth, and goodness— the basis for this list, I think, was not any clear evidence that those three are universal but rather a sense that three was a good-looking number.

There are other views about matter that I think are not based solely on the testimony of sense. For example, it is impossible

•for two bodies to occupy the same place at the same time,

•for one body to be in different places at the same time,

•for a body to be moved from one place to another without passing through some connected intermediate series of places.

These seem to be necessary truths, so they can’t be conclusions of our senses; for our senses testify only to what is, not what must be.

·SPACE·

Our next topic is our notion of space. Notice first that although space that is empty of matter isn’t perceived through any of our senses, when we perceive any of the primary qualities space presents itself as a necessary concomitant. There has to be space if there is to be extension, motion, shape, division, or cohesion of parts.

The notion of space enters into the mind through only two of our senses—namely touch and sight. If someone lacked both of these senses, I don’t see how he could ever have any conception of space. And even with both these senses, he still can’t have any notion of •space until he sees or feels other •objects . Space has no colour or shape to make it an object of sight; and it has no tangible quality to make it an object of touch. But other objects of sight and touch carry the notion of space along with them. And not only the notion but also the belief in it: a body couldn’t exist if there was no space to contain it, and it couldn’t move if there was no space ·for it to move through·. Its location, its distance from other bodies, and every other relation it has to other bodies, all presuppose space.

But though the notion of space seems not to enter the mind until it is introduced by the proper objects of sense, once it has been introduced it stays with us as something we conceive and in which we believe, even if the objects that introduced it have been removed. We see no absurdity in supposing a body to be annihilated while the space that contained it remains; and to suppose that to be annihilated seems to be absurd. •Empty space is so much allied to •nothing or •emptiness that it seems incapable of being annihilated or created.

As well as keeping a firm hold on our belief even when we suppose all the objects that introduced it to be annihilated, space swells to an infinite size. We can’t set any limits to how far it spreads or how long it lasts. Hence we call it

infinite, eternal, immovable, and indestructible.

But it is only

an infinite, eternal, immovable, and indestructible void or emptiness.

Perhaps we can say of it what the Aristotelians said of their ‘prime matter’, namely that whatever it is, it is potentially only, not actually.

When we consider parts of space that have a definite size and shape, there is nothing we understand better, nothing about which we can reason so clearly and to such a great extent. Extension and shape are circumscribed parts of space, and are the subject-matter of geometry—a science in which human reason has the widest field and can go deeper and with more certainty than in any other science. But when we try to grasp the whole of space, and to trace it to its origin, we get lost. The deep theorizings of able men on this subject differ so widely that we may well suspect that the line of human understanding is too short to reach the bottom of it.

I think Berkeley was the first to point out that •the extension, shape, and space that we talk about in ordinary language, and that geometry treats of, are basically perceived only by the sense of touch, but that •there is a notion of extension, shape, and space that can be acquired through sight without help from touch. To distinguish these he calls the first ‘tangible extension’, ‘tangible shape’, and ‘tangible space’, and the others ‘visible extension’ etc.

Because I think this distinction is very important in the philosophy of our senses, I shall adopt the names used for it by its discoverer, Berkeley, bearing in mind my previous point that space, whether tangible or visible, is not strictly speaking an object of sense but rather something that necessarily accompanies the objects both of sight and touch.

Please note also that when I use the names ‘tangible space’ and ‘visible space’ I don’t mean to follow Berkeley to the point of thinking that these are really •different things and altogether unalike. I take them to be •different conceptions of the same thing—one very partial and the other more complete, but each clear and sound as far as it goes.

Thus, when I see a spire at a very great distance it seems like the point of a needle; there appears to be no weathervane at the top, no angles. But when I see the same spire from close up, I see a huge pyramid with several angles and a vane at the top. Neither of these appearances is erroneous. Each is what it ought to be—what it must be for that sort of object seen at that distance. These different appearances of a single object illustrate the different conceptions of space—the conception based on the information of sight alone, and the conception drawn from the additional information of touch.

Our sight alone, unaided by touch, gives a notion of space that is very partial but clear. When space is considered according to this partial notion, I call it ‘visible space’. The sense of touch gives a much more complete notion of space, and when space is considered according to this notion I call it ‘tangible space’. There may be thinking beings of a higher order ·than us·, whose conceptions of space are much more complete than those we have from sight and touch combined. Another sense added to sight and touch might, for all I know, give us •conceptions of space that differed as much from •the ones we can now attain as •tangible space differs from •visible space; and those further conceptions might solve many knotty problems which we, because of the imperfection of our faculties, can’t possibly solve.

Berkeley acknowledges the visible shape and size of objects corresponds exactly with their tangible ·shape and size·, and that every detail in either of them has a corresponding detail in the other. He acknowledges also that Nature has established such a connection between the (1) visible shape and size of an object and (2) its tangible shape and size that we learn by experience to know (1) from (2) .We have been doing this all our lives, and we come to be so good and quick at it that we think we are seeing the tangible shape, size, and distance of bodies when really we only infer those tangible qualities from the corresponding visible qualities that are their natural signs.

[Then three paragraphs in which Reid likens the situation regarding how •visible shape etc. relates to •tangible shape etc. to the situation regarding how •our sensations relate to •the primary qualities with which they are connected. In each case, we are confronted by item x, which carries our mind immediately to item y, whereupon x is forgotten. Then:] Visible shape or size was never made an object of thought among philosophers until Berkeley gave it a name and pointed out •how it corresponds to and is connected with tangible size and shape, and •how the mind gets the habit of passing from visible shape as a sign to tangible shape as the thing signified by it, doing this so instantaneously that the visible shape is perfectly forgotten.

Visible shape, extension, and space can be made a subject of mathematical theorizing as well as tangible shape etc. can. Here are some differences between them:

Visible: two dimensions

Tangible: three dimensions

Visible: size measured by angles

Tangible: size measured by lengths of lines

Visible: every part is some definite proportion of the whole

Tangible: no part bears any proportion to the whole because the whole is immense [= ‘infinite’]

Such differences in their properties led Berkeley to think that visible size and shape are totally different from tangible size and shape—different and dissimilar, and not possibly belonging to the same object.

This dissimilarity is the basis for one of the strongest arguments in support of his system. It goes like this:

If there are external objects that have a real extension and shape, it must be either

•tangible extension and shape, or

•visible extension and shape, or

•both tangible and visible extension and shape.

The third option seems absurd; and no-one has ever maintained that a single object has two utterly dissimilar kinds of extension and shape. So only one of the two is really in the object, while the other extension and shape are ideal—·i.e. are in the mind and not in the object·. But ·which of the two should be awarded the reality prize? There is no basis for any answer·. No reason can be given for •selecting the perceptions of sight as real and declaring that those of touch are only ideal, or for •selecting the perceptions of touch as real and declaring those of sight to be only ideal. Anyone who is convinced that the objects of sight are only ideas has just as much reason to believe the same of the objects of touch.

But this argument loses all its force if something that I have already hinted at is true, namely that visible shape and extension are only a •partial conception, and tangible shape and extension a •more complete conception, of that ·unique and •complete· shape and extension that is, ·in all its •completeness·, really in the object.

Berkeley very thoroughly showed that sight alone, unaided by information from the sense of touch, gives us no perception of the distance from the eye of any object— indeed, it doesn’t even give us the thought of such a distance. But he wasn’t aware that this very principle overturns the argument for his system based on the difference between visible and tangible extension and shape. For supposing that external objects do exist, and have the tangible extension and shape that we perceive, it follows rigorously from the principle I have just mentioned that objects’ visible extension and shape must be just what we see it to be—·or, more accurately, it follows not from the principle that

sight, unaided, doesn’t yield the concept of distance from the eye,

but rather from the facts about how we do get the concept of distance from the eye, given that we don’t get it from unaided sight·.

The rules of perspective. . . .are demonstrable. They presuppose the existence of external objects that have tangible extension and shape; and on that basis the rules demonstrate what the visible extension and shape of such objects must be when they placed in such-and-such an orientation at such-and-such a distance.

So it becomes obvious that the visible shape and extension of objects, far from being •incompatible with tangible shape and extension, is a •necessary consequence of it in beings who see as we do. The correspondence between visible and tangible isn’t arbitrary, like the correspondence between words and the things they signify, as Berkeley thought. [Berkeley held that our visual states constitute a future-tense conditional language in which God tells us what we shall feel if we move thus and so.] Rather, the visible/tangible correspondence results necessarily from the nature of the two senses. Furthermore, this correspondence is always found in experience to be exactly what the rules of perspective say that it ought to be if the senses give true information; and that is an argument for both the truth of the rule and the truth of what our senses tell us.

Chapter 20: The evidence of the senses, and belief in general

It is obvious why Nature gave us the powers that we call the ‘external senses’. They are intended to give us such information about external objects as God saw to be appropriate for us in our present state; and they give to all mankind the information needed for survival, without reasoning or skill or investigation on our part.

The most uneducated peasant has as clear a conception of, and as firm a belief in, the immediate objects of his senses as does the greatest philosopher; and he is satisfied with this, not being interested in how he came by this conception and belief. But the philosopher is eager to know how his conception of external objects and his belief in their existence is produced. I’m afraid that this is hidden in impenetrable darkness. But the lack of knowledge leaves all the more room for conjecture; and philosophers have always been very liberal with that!

Plato’s dark cave and shadows, Aristotle’s ‘·sensible· species’, Epicurus’s films, and the modern philosophers’ ideas and impressions are all products of the human mind, successively invented to satisfy philosophers’ eager desire to know how we perceive external objects; but they all lack the two essential characters of a true and philosophical explanation of the phenomenon. [See the ‘first rule of philosophising’ laid down by ‘the great Newton’, Essay 1, late in chapter 3 here.] •We have no evidence that they exist, and •even if they did exist it can’t be shown how they would produce perception.

I have pointed out that this operation of perception contains two ingredients—•the conception or notion of the object, and •the belief in its present existence—and neither can be explained.

Most enlightened philosophers today, I think, agree that we can’t assign any adequate cause for our first conceptions of things. We know that we are built in such a way that in certain circumstances we have certain conceptions; but we don’t know how they are produced any more than we know how we were produced.

Once we have acquired through our senses conceptions of external objects, we can analyse them in our thought into their simple ingredients; and we can built those ingredients into various new compound forms that the senses never presented. But it is beyond the power of human imagination to form any conception whose simple ingredients aren’t provided by Nature in some manner that we can’t explain.

inner: We have a conception of the operations of our own minds,

outer: We have a conception of external objects,

inner: we have it immediately,

outer: we have it through our external senses,

inner: combined with a belief in their existence.

outer: combined with a belief in their existence.

inner: We call this ·combination of conception and belief· ‘consciousness’.

outer: We call this ·combination of conception and belief· ‘perception’.

But in each case we are only naming one of our sources of knowledge; we aren’t ·explaining it, i.e.· revealing its cause.

We know that when certain •impressions are made on our organs, nerves, and brain, certain corresponding •sensations are felt and certain objects are both •conceived and believed to exist. But in this sequence of operations Nature works in the dark. We can’t discover the cause of any one of them, or any necessary connection of one with another. Are they connected by some necessary tie or merely conjoined in our constitution by God’s will? We don’t know.

It seems very absurd to suppose that any kind of impression on a body should be the efficient cause of a sensation. Nor can we see any necessary connection between sensation and the conception of and belief in an external object. For all we can tell, we might have been constituted in such a way that we had all the sensations that we do actually have by our senses, without any ·preceding· impressions on our organs and without any ·following· conception of any external object. For all we know, we might have been made so as to perceive external objects without any impressions on bodily organs or any of the sensations that invariably accompany perception in us as we are actually constituted.

If our conception of external objects is inexplicable, the conviction and belief in their existence which we get by our senses is no less so.

‘Belief’, ‘assent’, ‘conviction’ are words that I don’t think admit of logical definition because the mental operation that they signify is perfectly simple, and of its own kind. But they don’t need to be defined, because they are common words and well understood.

[Reid and his contemporaries understood a ‘logical definition’ as one in which something complex is displayed in terms of its simpler ingredients, as in:

‘circle’ = ‘•plane figure that is •bounded by a line all the points on which are equidistant from a single point’.

Reid holds that ‘belief’ can’t be logically defined because the concept of belief is ‘simple’—it has no simpler ingredients that could be spread out in a definition.]

Belief must have an object: someone who believes must believe something; and this something is called the ‘object’ of his belief. Of this object of his belief he must have some conception, clear or obscure; for although there can be a clear and distinct conception of an object without any belief in its existence, there can’t be a belief without a conception.

Belief is always expressed in language by a proposition [= ‘sentence’ here and nearly everywhere in Reid] in which something is affirmed or denied. This is the form of speech that in all languages is assigned to that purpose; and if there were no belief there couldn’t be affirmations or denials, and we wouldn’t have any form of words to express either. Belief can be of different strengths, ranging from the slightest suspicion right up to the fullest assurance. These things are obvious to anyone who ever reflects; it would be an abuse of your patience if I went on about them.

I remark next that there are many operations of mind in which, when we analyse them as far as we can, we find belief to be an essential ingredient. A man can’t be conscious of his own thoughts without believing that he thinks. He can’t perceive an object of sense without believing that it exists. He can’t clearly remember a past event without believing that it did occur. Thus, belief is an ingredient in consciousness, in perception, and in remembering.

Belief is an ingredient not only in most of our •intellectual operations but also in many of the •active principles of the human mind. Joy and sorrow, hope and fear, imply a belief about good or ill either present or in expectation. Esteem, gratitude, pity, and resentment imply a belief about certain qualities in their objects. Anyone who acts for an end must believe that his act is likely to achieve that end. Belief has such a large a share in the sources of our intellectual operations, and in the operations themselves, that just as faith in God is represented as the mainspring in the life of a Christian, so also belief in general is the mainspring in the life of a man.

Men often believe things that there are no good reasons to believe, and are led by this into hurtful errors—that is too obvious to be denied. On the other hand, there are good reasons for some beliefs—that can’t be questioned either, except by someone who is a complete sceptic.

We label as ‘evidence’ anything that is a ground for belief. To believe without evidence is a weakness that every man has good reason to avoid and that every man wants to avoid. And it isn’t in a man’s power to believe anything for which he doesn’t think he has evidence. [In Reid’s time, ‘evidence’ could mean what it does to us, which is also what it seems to mean through much of this chapter. But sometimes in the chapter there are signs of the word’s being used in its other then-current meaning, namely evidentness: Reid’s phrase ‘the evidence of reasoning’ could mean ‘the evidentness that a proposition can have through being reached by reasoning’. Which meaning is involved in a given passage in this chapter is not always a clear-cut question; answering it is left to you.]

What this evidence is is more easily felt than described. Those who have never reflected on its nature still feel its influence in governing their belief. It is the logician’s business to explain its nature and to distinguish its various kinds and degrees; but every intelligent man can judge concerning it, and he commonly judges rightly when the evidence is fairly laid before him and his mind is free from prejudice. A man who •knows nothing of the theory of vision may •have a good eye; and a man who •never theorized about evidence in the abstract may •have good judgment.

Everyday concerns lead us to distinguish evidence into different kinds, to which we give names that are well understood—such as

evidence of the senses,

evidence of memory,

evidence of consciousness,

evidence of testimony,

evidence of axioms,

evidence of reasoning.

All men of ordinary intelligence agree that each of these kinds of evidence can provide good grounds for belief, and they pretty much agree about what details in a piece of evidence would strengthen or weaken it.

Philosophers have tried by analysing the different sorts of evidence to discover some common nature in which they all share, thereby to reducing them all to one. This was the aim of the schoolmen in their intricate disputes about the criterion of truth. Descartes placed this criterion of truth in clear and distinct perception, and laid it down as a maxim that

•whatever we clearly and distinctly perceive to be true is true;

but what he means by ‘clearly and distinctly perceive’ in this maxim it’s hard to say! Locke placed the criterion in a perception of the agreement or disagreement of our ideas, this perception being •immediate in •intuitive knowledge, and •by the intervention of intervening ideas in •reasoning.

I think I have a clear notion of the different kinds of evidence I have listed, and perhaps of some others that I needn’t list here; but I have to say that I can’t find any nature that is common to them all, defining a common kind to which they all belong. They seem to me to agree only in this: they are all fitted by Nature to produce belief in the human mind, some of them in the highest degree (which we call ‘certainty’), others in various degrees according to circumstances.

I shall take it for granted that the evidence of the senses, when the proper circumstances are in place, is good evidence and a sound basis for belief. My intention here is only to set it alongside the other kinds that I have listed, so that we can judge whether it is a special case of any of them or rather is a nature special to itself.

Evidence of the senses seems to be quite different from the evidence of reasoning. All •good evidence is commonly called ‘reasonable’ evidence, and rightly so, because •it ought to govern our belief as reasonable creatures. And in line with this label I think that the evidence of the senses is just as ‘reasonable’ as the evidence of demonstration. If Nature informs us about things that concern us, by means other than reasoning, reason itself will direct us to accept that information gratefully and to make the best use of it.

But when we speak of ‘evidence of reasoning’ as a particular kind of evidence, we are talking about the evidence of propositions that are inferred by reasoning from propositions already known and believed. Thus the evidence of the fifth proposition of the first book of Euclid’s Elements consists in its being shown to be the necessary consequence of the axioms and preceding propositions. In all reasoning there must be one or more premises and a conclusion drawn from them. And the premises are called ‘the reason why’ we must believe the conclusion which we see to follow from them.

That the evidence of the senses is of a different kind from this needs little proof. No-one looks for a reason for believing what he sees or feels! And if someone did, it would be hard to find one. But though a man can give no reason for believing his senses, his belief remains as firm as if it were grounded on demonstration.

Many eminent philosophers have thought it unreasonable to believe when they couldn’t show a reason, and this has led them to work to provide us with reasons for believing our senses. But their reasons are very weak, and won’t bear examination. Other philosophers have shown very clearly the defects of these reasons, and have (so they think) discovered invincible reasons against •this belief ·in the senses·; but they have never been able to shake •it off in themselves, or to convince others. The statesman continues to plot, the soldier to fight, and the merchant to export and import, without being in the least moved by the demonstrations that have been offered of the non-existence of the things they are so seriously employed about. You have as much chance of arguing the moon into leaving its orbit as you have of destroying by argument anyone’s belief in the objects of the senses. [Reid wrote ‘the stateman continues to plod’; but in his day one of the meanings of ‘plod’ was plot.]

[Then three paragraphs arguing against the thesis that ‘the evidence of the senses is the same as the evidence of axioms or self-evident truths’. This, Reid says, misuses the word ‘axiom’ and ignores the fact that sense-attested propositions, however secure, are not ‘necessary and immutable’. Then:]

There is no doubt an analogy between the evidence of the senses and the evidence of testimony. That is why we find in all languages such analogical expressions as ‘the testimony of our senses’, ‘of giving credit to our senses’, and the like. But there is a real difference between the two as well as a similarity. When we believe something on the basis of someone’s testimony, we rely on that person’s authority. But we have no such authority for believing our senses.

Shall we say then that this belief is God’s inspiration? I think there is a sense in which that is true, because I take the belief in question to be the immediate effect of our constitution, which is God’s work. But if ‘inspiration’ is understood to imply a conviction that it comes from God, our belief in the objects of the senses is not inspiration; for a man would believe his senses even if he had no notion of any god. Someone who is convinced that he is the workmanship of God, and that it is a part of his constitution to believe his senses, may think that to be a good reason to confirm his belief. But ·it won’t be the basis for the belief, because· he had the belief before he could give this or any other reason for it.

If we compare the evidence of the senses with that of memory, we find a great resemblance but still some difference.

memory: ‘I clearly remember dining yesterday with Mr Stewart’—what does that mean?

senses: ‘I see a chair to my right.’ What does that mean?

memory: It means that I have a distinct conception of and firm belief in this past event—not by reasoning, not by testimony, but immediately from my constitution.

senses: It means that I have by my constitution a distinct conception of and firm belief in the present existence of the chair in that place.

memory: I give the name ‘memory’ to the part of my constitution by which I have this kind of conviction regarding past events.

senses: I give the name ‘seeing’ to the part of my constitution by which I have this immediate conviction.

The two operations agree in the immediate conviction that they give. They agree also in that the things believed are not necessary but contingent and limited to time and place. But they differ in two respects. (1) The object of memory must have existed at some •past time; but the object of sight—and of all the other senses—must be something that exists at •present. (2) I see only by my eyes, and only when they are directed to the object and when it is illuminated; but my memory isn’t tied down to any bodily organ that I know of, or limited by light and darkness—though it does have limitations of another kind.

These differences are obvious to all men, and very reasonably lead them to consider seeing and remembering as operations of fundamentally different kinds. But the nature of the evidence they give has a great resemblance. A comparable difference and a comparable resemblance obtains between the evidence of the senses and the evidence of consciousness; I leave this for you to work out for yourself.

As for ·Locke’s· opinion that evidence consists in a perception of the agreement or disagreement of ideas, I may have occasion to consider it in more detail in another place. All I will say here is that this thesis, when taken in its most favourable sense, does fit the evidence of reasoning and the evidence of some axioms. But I can’t see how it can be applied in any sense to the evidence of consciousness, or of memory, or of the senses.

When I compare the different kinds of evidence that I have listed, I have to say that the evidence of •reasoning and of some •necessary and self-evident truths seems to be the least mysterious, the most completely understood; so I am not surprised that philosophers should have tried to reduce all kinds of evidence to these.

When I see that a proposition is self-evident and necessary, and that its subject is plainly included in its predicate, I seem to have everything I need to understand why I believe it. And when I see that a consequence necessarily follows from one or more self-evident propositions, that is all I need for believing that consequence. The light of truth so fills my mind in these cases that I can’t want or ·even· conceive anything more satisfying.

When I clearly remember a past event or see an object before my eyes, this commands my belief just as much as an axiom does. But when as a philosopher I reflect on this belief, and want to trace it to its origin, I can’t resolve it into necessary and self-evident axioms or into conclusions that necessarily follow from them. It seems that I don’t have that kind of evidence—the kind that I can best comprehend and that gives perfect satisfaction to an inquisitive mind—and yet it would be ridiculous to doubt, and anyway I find that I can’t doubt. Trying to throw off this belief is like trying to fly—ridiculous and impracticable.

To a philosopher, one who has long thought that his knowledge is chiefly due to the acquisition of the reasoning power that he is so proud of, it is no doubt humiliating to find that his reason can lay no claim to the greater part of what he knows. Through his reason he can discover certain abstract and necessary relations of things; but his knowledge of what really does or did exist comes though another channel—one that is open to those who cannot reason. He is led to it in the dark, and doesn’t know how he got there.

It’s not surprising that the pride of philosophy should lead some philosophers to invent empty theories in order to account for this knowledge; and that others, who see that this can’t be done, spurn a ·kind of· knowledge they can’t account for, and vainly try to get rid of it as a reproach to their understanding. But the wise and the humble will receive it as the gift of heaven, and try to make the best use of it.

Chapter 21: Improving the senses

Our senses can be thought of in two ways—(1) as givers of pleasant or unpleasant sensations, and (2) as givers of information about things that concern us.

[Reid then devotes about a page to saying that the senses in the first of their two roles can’t be improved and don’t need to be. Some of his points: •Nasty sensations are Nature’s way of warning us of impending trouble. •It can happen that an intensely nasty kind of sensation, when repeated often enough, flattens out to being tolerable and eventually neutral. Similarly with a pleasant kind, flattening out into ‘insipid’ and perhaps even worse. This is in contrast to ‘our active and perceptive powers’, which intensify with frequent use. •If you try ‘by a soft and luxurious life’ to develop your capacity for pleasant sensations, you’ll do the same for your capacity for unpleasant ones; and you will ‘encourage many diseases that cause pain’. Then:]

The improvement of our external senses in their role as givers of information is a subject more worthy of our attention. The external senses aren’t the noblest and most exalted powers of our nature, but they aren’t the least useful. All that we can know about the material world must be based on information that they give, and everyone—the philosopher as well as the day-labourer—must be indebted to them for most of his knowledge.

Some of our perceptions by the senses could be called •‘original’ ·or ‘basic’·, because they don’t require any previous experience or learning; but ever so many more of our perceptions are •acquired ·or learned·, and are the fruit of experience.

[Reid applies this distinction to the senses of smell, taste, and hearing, repeating some of what he has said earlier about secondary qualities. Then:]

We know much more about the world through the other two senses. By sight we learn to distinguish objects by their colour, in the same way that we distinguish them by their sound, taste, and smell. By this sense we perceive visible objects to have •extension in two dimensions, •visible shape and size, and •a certain angular distance from one another. These I take to be the original perceptions of sight.

By the sense of touch we not only perceive whether bodies are hot or cold (which are secondary qualities), but we also perceive originally their •three dimensions, their •tangible shape and size, their •distance from one another, and their •hardness or softness or fluidity. We originally perceive these ·primary· qualities by touch alone, but through experience we learn to perceive most of them by sight.

We learn to perceive by one sense what originally could have been perceived only by another, doing this by finding a connection between the objects of the different senses. The original perceptions or the sensations of one sense become signs of whatever has always been found connected with them; and from the sign the mind passes immediately to the conception of and belief in the thing signified. And although the connection in the mind between the sign and the thing signified by it is an effect of custom—·which means that it has been learned·—this custom becomes second nature, making it hard to distinguish from the original power of perception.

For example, if a sphere of one uniform colour is placed in front of me, I easily perceive by my eye its spherical shape and its three dimensions. Everyone will agree that just by looking and without touching I can be certain that it is a sphere; but it is equally certain that by the original power of sight I couldn’t perceive it to be a sphere and to have three dimensions. The eye originally could only perceive two dimensions and a gradual variation of colour on the different sides of the object.

It’s from experience that we learn that the variation of colour is an effect of the spherical shape and of the distribution of light and shade. But our thought moves so fast from the effect to the cause—·from the colour-variation etc. to •the object’s being a three-dimensional sphere·—that we attend only to •the cause and can hardly be persuaded that we don’t immediately see the three dimensions of the sphere. . . .

[Reid proceeds to re-tell this story in terms of signs and things signified. Then:]

Those who have had their eyesight from infancy come to have acquired perceptions so early that they can’t remember ever not having them; so they don’t distinguish them from their original perceptions; and can’t be easily persuaded that there is any solid basis for such a distinction. . . .

This power that we acquire of perceiving through our senses things that originally we wouldn’t have perceived is not the effect of any reasoning on our part. It’s the result of our constitution—·the way we are made·—and of the situations in which we happen to be placed. We are made in such a way that when two things are found to be conjoined in certain circumstances, we are prone to believe that they are connected by Nature and will always be found together in similar circumstances.

This belief isn’t intuitively obvious, nor do we get it through reasoning; I think it is an immediate effect of our constitution. So it is strongest in infancy, before our reasoning power appears, before we are able to draw a conclusion from premises. Suppose a child once burns his finger in a candle: from that single event he connects the pain of burning with putting his finger in the candle, and believes that these two things must go together. This part of our constitution is obviously very useful to us before we come to the use of reason. . . .

No doubt someone’s being perfectly rational would show in his having no beliefs except ones based on intuitive evidentness or on sound reasoning. But man is not perfectly rational, and Nature doesn’t intend that he should be so at every moment of his life. We come into the world without the use of reason; before we are •rational creatures we are merely •animal; and our survival depends on our believing many things before we can reason. . . . Our beliefs at that time are not governed by chance. They are regulated by certain principles that are parts of our constitution. Call them ‘animal principles’ or ‘instinctive principles’ or what you will; the name doesn’t matter; what matters is that they are different from the faculty of reason. They do the work of reason while it is in its infancy. . . .

From what I have said you will see that our original powers of perceiving objects by our senses are greatly improved by use and habit. . . . This is the greatest and most important improvement of our external senses. . . .

Besides this •natural improvement of our senses, there are various •artificial ways in which they can be improved, or their defects remedied. (1) By proper care of the organs of sense, this being a medical matter. . . .

(2) By accurate attention to the objects of sense. [In this passage, ‘artist’ refers to anyone who practises a skill or technique—a painter, a physician, a plumber, etc. And similarly with ‘art’.] In every art we can see how such attention improves the senses. The artist, by giving more attention to certain objects than others do, comes to perceive many things in those objects that others don’t. And many people who happen to be deprived of one sense make up for that defect to a large extent by attending more carefully to the objects of the senses they do have. The blind have often been known to acquire unusual sharpness in distinguishing things by touch and hearing; and the deaf are better than the rest of us at reading men’s thoughts in their faces.

(3) Our senses can be improved also by additional artificial organs or instruments. . . .

(4) Information acquired by our senses can be improved by discovering how Nature has connected objects’ sensible qualities with their more hidden qualities. . . . I am taught that bodies belonging to a certain species have certain hidden qualities, but how am I to know that this individual belongs to that species? Only through the sensible qualities that characterise the species; I must know that this is bread and that is wine before I eat the one or drink the other. . . .

It is one branch of human knowledge to •know the names of the various species of natural and artificial bodies, and to •know the sensible qualities by which things are recognized as members of them. It is another branch of knowledge to •know the hidden qualities of the various species, and the uses to which they can be put. Someone who possesses both these branches is informed by his senses of countless important things that are hidden from those who possess only one, or neither. . . .

Chapter 22: The deceptiveness of the senses

Complaints that our senses are deceptive have been very common in ancient and in modern times, especially among philosophers. If we accepted everything they have said on this subject, it would seem natural for us to conclude that

some malignant demon gave us our senses so as to delude us,

rather than that

our senses were formed by God, who is wise and beneficent, so as to give us true information about things we need to know for our survival and happiness.

The whole sect of atomists. . . .maintained that all the qualities of bodies that the moderns call ‘secondary qualities’. . . .are mere illusions of sense and have no real existence. Plato maintained that we can get no real knowledge of material things, and that eternal and unchanging ideas are the only objects of real knowledge. The. . . .sceptics anxiously hunted up arguments to prove the deceptiveness of our senses, in support of their favourite doctrine that we ought to withhold assent even in things that seem most evident.

Among the Aristotelians we find frequent complaints that the senses often deceive us, and that their testimony is suspect when it isn’t confirmed by reason, which can correct the errors of the senses. They supported this complaint by many everyday examples, such as the crooked appearance of an oar in water; objects being magnified and their distance mistaken in a fog; the sun and moon appearing to be about a foot or two in diameter, when really they are thousands of miles ·across·; a square tower being taken at a distance to be round. They believed that the deceptiveness of the senses sufficed to explain these appearances and many others like them. So they were using ‘the deceptiveness of the senses’ as a decent cover to conceal their ·shameful· ignorance of the real causes of the phenomena—the same role that had been found for ‘occult qualities’ and ‘substantial forms’.

Descartes and his followers joined in the same complaint. [Reid then brings in the Cartesian philosopher le Grand, from whom he quotes a passage about the deceptiveness of the senses, ending with this:] ‘The senses are given by Nature for just one purpose, namely to warn us of what is useful and what is hurtful to us. We pervert the order of Nature when we put them to use in another way, namely as a means to knowledge of truth.’. . . .

It seems to taking a poor view of God’s workmanship to think that he has given us one faculty (our senses) to deceive us and another faculty (reason) to detect the deception!

So we ought to consider whether the ·belief in the· deceptiveness of our senses isn’t rather a common error that men have been led into in an attempt to conceal their ignorance or to apologise for their mistakes.

There are two powers that we owe to our external senses— •sensation and •the perception of external objects. There can’t be anything deceptive in sensation, because we are conscious of all our sensations, and ·therefore· they can’t be different in kind, or more or less intense, than we feel them to be. A man can’t possibly be in pain when he doesn’t feel pain; and when he feels pain it is impossible that his pain shouldn’t be real and be as intense as he feels it to be; and the same thing goes for every sensation whatsoever. A pleasant or unpleasant sensation may be forgotten when it is •past, but when it is •present it can’t be other than what we feel.

So if there is anything deceptive in our senses, it must be in the perception of external objects, which is my next topic.

Our powers of perceiving external objects aren’t the best conceivable; perhaps beings of some higher order have more perfect powers than ours. We can perceive external objects only by means of bodily organs; and these are liable to various disorders that sometimes affect our powers of perception. The nerves and brain, which are interior organs of perception, are also as liable to disorders as every part of the human frame is.

But it’s not only our powers of perception that are all liable to be hurt or even destroyed by disorders of the body; the same thing is true of the imagination, the memory, and the powers of judging and reasoning—but that doesn’t lead us to call them deceptive!

Our senses, our memory, and our reason are all limited and imperfect. That is the human fate. But they are such as God saw to be best fitted for us in our present state. Superior beings may have intellectual powers that we don’t have at all, or have ones that we also have but less perfectly than they do and more liable to accidental disorders than theirs are. But we have no reason to think that God has given deceptive powers to any of his creatures. This would be to think dishonourably of our maker, and would lay a basis for universal scepticism.

The appearances commonly imputed to the deceptions of the senses are many and various, but I think they can be placed in the four following classes.

(1) Many things called deceptions of the senses are only conclusions rashly drawn from the testimony of the senses. In these cases, the testimony of the senses is true but we rashly draw from it a conclusion that doesn’t necessarily follow. We are disposed to blame our errors on false information rather than on inconclusive reasoning, blaming our senses for the wrong conclusions we draw from their testimony. [Reid illustrates this at some length, e.g. by the example of someone who is taken in by a counterfeit coin. And then moves on to something that seems to be of intrinsic interest to him, not merely—not even mainly—as raising issues about the deceptiveness of the senses. Thus:]

Many false judgments that are regarded as deceptions of the senses arise from our mistaking •relative motion for •real or absolute motion. These mistakes can’t be deceptions of the senses because:

by our senses we perceive only the relative motions of bodies; it is by reasoning that we infer real ·or absolute· motion from the relative motion that we perceive.

A little reflection can satisfy us of this.

I noted earlier that we perceive extension to be one sensible quality of bodies, which inevitably leads us to conceive space, though space itself isn’t an object of sense. When a body is moved out of its place, the space that it filled remains empty until it is filled by some other body; and if it were never filled in that way it would remain empty forever. Before any bodies existed, the space they now occupy was empty space, capable of receiving bodies; for no body can exist where there is no space to contain it. Thus, there is space wherever bodies exist or can exist.

This makes it obvious that space can’t have any limits. It is equally obvious that space is immovable. Bodies in space are movable, but the place where they are can’t be moved—we can no more think of •one part of space as moving nearer to or further from another than we can think of •a thing as being moved away from itself!

This unlimited and immovable space is what philosophers call ‘absolute space’. •Absolute or real motion is a •change of place in absolute space.

Our senses don’t inform us of the absolute motion or absolute immobility of any body. When one body moves away from another, this can be picked up by the senses; but we don’t perceive by our senses whether any body keeps to the same part of absolute space. When one body seems to move away from another, we can infer with certainty that absolute motion has occurred; but our senses don’t tell us whether the absolute motion was in this body or that body or both.

[Reid then introduces the formerly widespread belief that ‘the earth keeps its place unmoved’; says that it would be interesting to have an explanation of its popularity and of people’s tendency to cling to it even in times when we all know better; says explicitly that such an explanation ‘is not our present business’; and proceeds with the supposedly more limited project of showing that this popular error ‘cannot justly be called a deception of the senses’. Thus:]

All motion must be estimated from some point or place that is supposed to be at rest. We don’t perceive the points of absolute space from which real and absolute motion must be reckoned. And there are obvious reasons why mankind in a state of ignorance should make the earth the fixed place from which to estimate the various motions they perceive. The practice of doing this from infancy, and of constantly using a language that supposes the earth to be at rest, may perhaps be the cause of the general prejudice in favour of this opinion. [‘not our present business’!]. . . .

(2) Another class of errors that are blamed on the deceptions of the senses are the ones we are liable to in our learned perceptions. [Reid repeats his earlier explanation of ‘learned perceptions’. Then:] Whether this learned perception •is a process of reasoning that we no longer remember (as some philosophers think) or rather •results from some part of our constitution distinct from reason (as I believe), is not relevant to our present topic. If the former view is right, the errors of learned perception belong in class (1) that I have already discussed. If not, they are in a distinct class of their own. Either way, the errors of learned perception are not deceptions of our senses.

[Reid then gives several examples, including the example of the sphere. The closing paragraphs of this segment of the chapter explain why it is good for us to have learned perceptions, especially in childhood—which Reid describes with great charm and insight. Thus:]

We come into the world ignorant of everything, and exposed by our ignorance to many dangers and to many mistakes. The regular sequence of causes and effects that God in his wisdom has established, and that directs every step of our adult conduct, is unknown until it is gradually discovered by experience.

We must learn a lot from experience before we can reason, so we are likely to make many errors. Indeed I think that in our early years reason would do us much more harm than good. If we were aware of our condition in that period of life, and could reflect on it, we would be like a man in the dark surrounded with dangers, where every step he takes may be into a pit. Reason would direct him to sit down and wait until he could see around him.

Similarly, if an infant were endowed with reason it would direct him to do nothing until he knew what could be done safely. He can know this only by trying things out, and experiments are dangerous. Reason directs that dangerous experiments shouldn’t be conducted unless there is a very urgent reason. So reason, ·if the infant had it·, would make him unhappy and would get in the way of his learning through experience.

Nature has followed another plan. The child, unaware of danger, is led by instinct to exert all his active powers to •try everything without the cautious warnings of reason, and to •believe everything he is told. Sometimes his rashness brings him harm that reason would have prevented. But his suffering is itself a useful discipline, leading him to avoid in future whatever caused it. Sometimes •his credulity leads to his being misled, but •it is infinitely beneficial to him on the whole. His activity and credulity are more useful qualities, and better instructors, than reason would be: they teach him more in a day than reason would do in a year; they provide a stock of materials for reason to work on; they make him relaxed and happy at a time in his life when reason could only serve to suggest a thousand tormenting anxieties and fears. And even when he •does things and •believes things that reason wouldn’t justify, he is acting ·and believing· in conformity with Nature’s intention and with the constitution it gave him. So that the wisdom and goodness of the author of Nature can be seen just as clearly in withholding the exercise of our reason in infancy as in bestowing it when we are ready for it.

(3) A third class of errors ascribed to the deceptions of the senses proceeds from ignorance of the laws of Nature.

The laws of Nature (I mean physical laws, not moral ones) are learned either from our own experience or from the experience of others who have had the opportunity to observe the course of Nature.

Ignorance of those laws, or inattention to them, is apt to lead to false judgments concerning the objects of the senses, especially those of hearing and of sight. Those false judgments are often called ‘deceptions of the senses’, but that is not what they are.

Sounds affect the ear differently depending on whether the bell (for example) is in front of us or behind, on the right hand or on the left, near or far away. We learn to judge where the bell is on the basis of how its sound affects the ear, and in most cases we judge correctly. But we are sometimes deceived by •echoes that bounce the sound back, or •whispering galleries that alter its direction, or •speaking trumpets that convey it across a distance without lessening.

Ventriloquists are people who have acquired the art of modifying their voice so that it affects the hearer’s ear as if it came from another person or from the sky or from under the earth. The deception they produce is still greater ·than those I have just listed·, because it is less common than they are. Well, the deception they are said to produce! I never had the good fortune to hear one of these artists at work, so I can’t say how perfect their art has become. [In Reid’s time an ‘art’ was any human activity involving techniques or rules or skills, including medicine, farming, painting—and ventriloquism!] I suspect that it is very imperfect imitation, and not apt to deceive anyone who isn’t inattentive or flustered. If ventriloquism could be carried to perfection, the ventriloquist would be a very dangerous man in society. . . . And if the ventriloquists have all been too virtuous to use their talent to the harm of others, we might at least expect that some of them would use it for their own benefit. If it could be brought to any significant degree of perfection, it seems to be as legitimate a device for getting money as conjuring or rope-dancing. But I have never heard of any exhibition of this kind, which inclines me to think that it is too crude an imitation to stand being publicly exhibited, even to the vulgar.

Some people are said to have the art of imitating the voice of someone else so exactly that in the dark they might be taken for the person whose voice they are imitating. I am apt to think that the stories told about this art are also exaggerated—as amazing stories are apt to be—and that an attentive ear would be able to distinguish the copy from the original.

Here is a wonderful example of how accurate [here = ‘fine-grained’, ‘sensitive’] as well as of how truthful our senses are in matters that are of real use in life: we can distinguish all the people we know by their faces, voices, and hand-writing, although we are often unable to say what tiny differences we are going by when we identify them; and we are hardly ever deceived in matters of this kind, when we give proper attention to what the senses tell us.

But when it does happen that sounds produced by different causes are not distinguishable by the ear, this may prove that our senses are •imperfect but not that they are •deceptive. The ear may not be able to draw the right conclusion, but it’s only our ignorance of the laws of sound that leads us to a wrong conclusion.

Deceptions of •sight arising from ignorance of the laws of Nature are more numerous and more remarkable than those of •hearing.

The rays of light that are our means of seeing travel in straight lines from the object to the eye when they aren’t obstructed, and we are naturally led to conceive the visible object to be in the direction of the rays that reach the eye. But the rays can be reflected, refracted, or inflected [= ‘bent’] in their journey from the object to the eye, according to certain fixed laws of Nature, and this can change their direction, thereby changing the apparent place, shape, or size of the object.

Thus, a child sees himself in a mirror and thinks he sees another child behind the mirror imitating all his motions. But even a child soon gets the better of this deception and knows that he sees only himself.

All the deceptions made by telescopes, microscopes, camera obscuras, and magic lanterns are of the same kind, though less familiar to the vulgar. Ignorant people may be deceived by them; but to those who know the principles of optics they give solid and true information, and the laws of Nature by which they are produced bring infinite benefit to mankind.

(4) There remains one further class of errors commonly called ‘deceptions of the senses’—these are the only ones that I think can properly be given that label. I mean the deceptions that come from some disorder or abnormal state either of the •external sense-organ or of the •nerves and brain that are internal organs of perception.

In a delirium or in madness, perception, memory, imagination, and our reasoning powers are strangely disordered and confused. There are also disorders that affect some of our senses while others are sound. Thus, a man can feel pain in his toes after the leg has been cut off. If you hold a small ball between your crossed fingers, you may feel it as two balls. You may see an object double by not directing both eyes properly to it. By pressing the ball of your eye you can see colours that are not real. Someone with jaundice in his eyes may mistake colours. These are more properly called ‘deceptions of the senses’ than any of classes (1) through (3).

We have to accept that it comes with being human that all our faculties are liable, through accidental causes, to be hurt and wholly or partly unfitted for their natural functions. But as this imperfection is common to •all our faculties, it provides no sound basis for picking out •some of them as deceptive.

Summing up: it seems to have been a common error of philosophers to regard the senses as deceptive. And to this error they have added another: that one use of reason is to detect the deceptions of the senses.

From what I have said I think it appears that there is no more reason to account our •senses as deceptive than our •reason, our •memory, or any other •faculty of judging that Nature has given us. They are all limited and imperfect, but are wisely suited to the present condition of man. We are liable to error and wrong judgment in the use of them all; but no more in the information provided by the senses than in the deductions of reasoning. And the errors we fall into regarding objects of the senses are corrected not •by reason but •by more accurate attention to the input we get from our senses themselves.

Perhaps philosophers’ pride gave rise to this error ·of thinking that reason has the task of correcting the supposed deceptions of the senses·. They think that reason is what puts them on a higher level than uneducated people. The testimony of the senses are common to the philosopher and to the most illiterate. They put all men on a level, and so they’re apt to be undervalued ·by educated people·. But we are indebted to the testimony of the senses for most of our knowledge, and for the most interesting part of it. The wisdom of Nature has made the most useful things the most common, and their commonness shouldn’t lead us to despise them. Nature also pressures us to believe the testimony of the senses, and philosophy’s attempts to weaken that force are all fruitless and vain.

One last remark on this topic: There seems to be a contradiction between •what philosophers teach concerning ideas and •their doctrine of the deceptiveness of the senses. We are taught that the role of the senses is only to give us the ideas of external objects. If that is right, there can’t be any deceptiveness in the senses: ideas can’t be true or false; if the senses don’t testify anything they can’t give false testimony; if they aren’t judging faculties, no judgment—whether true or false—can be attributed to them. So there is a contradiction between •the common doctrine concerning ideas and •the common doctrine concerning the deceptiveness of the senses. Both could be false, as I believe they are; they can’t both be true.

Essay 3: Memory

Chapter 1: Obvious and certain truths about memory

Chapter 2: Memory is an original faculty

Chapter 3: Duration

Chapter 4: Identity

Chapter 5: Locke’s account of the origin of our ideas, especially the idea of duration

Chapter 6: Locke’s account of our personal identity

Chapter 7: Theories about memory

Chapter 1: Obvious and certain truths about memory

In a man’s gradual progress from infancy to maturity, his faculties come into play in a certain order, and that order seems to be the best one to follow in discussing the faculties. The external senses appear first; memory next; so now I turn to memory. Memory is what gives us immediate knowledge of things past. The senses inform us about things only as they exist in the present moment, and if this information were not preserved by memory it would vanish instantly, leaving us as ignorant as if it had never been.

Memory must have an object. Everyone who remembers must remember something, and the item that he remembers is called ‘the object’ of his remembering. Memory is like perception in this respect, and unlike sensation, which has no object but the feeling itself. Everyone can distinguish •the thing remembered from •the remembering of it. We may remember anything that we have seen or heard or known or done or undergone, but the remembering of it is a particular act of the mind which exists now and of which we are conscious. . . .

When we perceive an object by our senses, a certain sequence of operations—tied together by our constitution— takes place:

•The object makes some impression on the sense-organ, either immediately or through some medium.

•This leads to an impression’s being made on the nerves and brain.

•That results in our feeling some sensation.

•And that sensation is accompanied by the conception of and belief in the external object that we call ‘perception’.

These operations are so connected in our constitution that it’s hard to separate them in our thought, attending to each without confusing it with the others. But in memory we don’t find any sequence of operations like that one, and this frees us from the difficulty-of-separating embarrassment: rememberings are easily distinguished from all other acts of the mind, and they are free from all ambiguity.

The object of memory—i.e. the thing remembered—must be something that is •past, just as the object of perception and of consciousness must be something that is •present. What happens now can’t be an object of memory, and something that is past and gone can’t be an object of perception or of consciousness.

Memory is always accompanied by a belief in what we remember, just as perception is accompanied by a belief in what we perceive, and consciousness by a belief in what we are conscious of. Perhaps in infancy or in a mental disorder someone can confuse remembered things with things that are merely imagined; but every mentally healthy adult feels that he must believe anything that he clearly •remembers, even though he can give no reason for his belief except that he remembers the thing clearly, whereas when he merely •imagines a thing—however clearly—this doesn’t lead him to believe in its existence.

We regard this belief that we have from clear memory as real knowledge, and as being no less certain than if it had been based on demonstration; no sane man calls it in question or will hear any argument against it. The testimony of witnesses in trials where the accused’s life is at stake depends on, it and all mankind’s knowledge of past events is built on this foundation.

Sometimes a man’s memory is less clear and definite, and then he is ready to allow that it can have failed him; but this doesn’t in the least weaken its credibility when it is perfectly clear.

Memory implies a conception of past time and a belief that some time has passed; for it is impossible that a man should now clearly •remember x without •believing that some stretch of time, large or small, has passed between the time when x happened and now; and I think it is impossible to show how we could acquire a notion of duration if we had no memory.

Things remembered must be things formerly perceived or known. . . .

The remembering of a past event is necessarily accompanied by the rememberer’s belief that he existed at the time when the event happened. I can’t remember something that happened a year ago without a conviction, as strong as memory can give, that I—the very same identical person who now remembers that event—did exist a year ago.

I regard what I have said about memory up to here as principles that will appear obvious and certain to everyone who takes the trouble to reflect on the operations of his own mind. They are factual claims that you must judge on the basis of what you feel; they admit of no proof except an appeal to everyone’s own reflection. So I shall take them for granted in what follows. I shall first (·chapters 2-4·) draw some conclusions from them, and then (·chapters 5-7·) examine the theories of philosophers concerning •memory, •duration, and •our personal identity—which ·comes in here because· we acquire the knowledge of it by memory.

Chapter 2: Memory is an original faculty

[In calling memory an ‘original’ faculty Reid means, at least in part, that it is basic, and not the upshot of combining two or more faculties that are more basic and more general. That is why we can’t explain it. An explanation, Reid thinks, would have to be something along the lines of ’To remember x is to combine the upshots of mental actions of types A and B in relation to x’; and that would mean that A and B were more basic than memory, implying that memory is not ‘original’.]

First, I think it appears that memory is an original faculty that God has given us, and that we can’t give any explanation of it except ‘That’s the way we are made’.

The knowledge that my memory gives me of •past events seems to me as unexplainable as would be an immediate knowledge of •future events; and I can’t explain why I should have the •former and not the •latter except that that is God’s will. . . .

When I believe the truth of an axiom or other mathematical proposition, I see that it must be so. Everyone who has the same conception of it sees the same. There is a necessary and evident connection between the subject of the proposition and its predicate, and I have all the evidence to support my belief that I can possibly conceive.

When I believe that I washed my hands and face this morning, no necessity shows up in the truth of this proposition—it could be true but it might not be. A man can clearly •conceive it without believing it at all. Then how do I come to believe it? By remembering it distinctly. That’s all I can say. This remembering is an act of my mind. Isn’t it possible that this act should occur without the event’s having happened? I have ·to answer ‘Yes, as far as I know’, i.e.· to say that I don’t see any necessary connection between the present act and the past event. If someone does show such a necessary connection, then I think we’ll have an explanation for the belief that we have in what we remember; but if this can’t be done, that belief can’t explained except by saying that it’s a result of how we are built.

‘But the experience we have had of memory’s trustworthiness is a good reason for relying on its testimony.’ I don’t deny that this can be a reason for those who have had this experience and who reflect on it. But I don’t think that many people have ever thought of this reason, or thought they needed it. It would have to be some very special circumstance that led a man to have recourse to it; and even those who have used that argument must have trusted the testimony of memory before having any experience of its trustworthiness. . . .

We sometimes ·come to· know an abstract truth by comparing the terms of the proposition that expresses it and perceiving some necessary relation or agreement between them. That’s how I know that two and three make five, that the diameters of a circle are all equal. Locke discovered this source of knowledge and then rushed on to concluded that all human knowledge can be derived from it; and he has been very generally followed in this, especially by Hume.

But I can see that our knowledge of the existence of contingent things can’t ever be traced back to this source. I know that a certain thing x does or did exist. This knowledge can’t be derived from the perception of a necessary agreement between •existence and •x, because there is no such necessary agreement. . . . The thing x doesn’t exist necessarily, but by the will and power of God who made it; and no contradiction follows from supposing x not to exist.

This implies, I think, that our knowledge of the existence of our own thoughts, of the existence of all the material objects around us, and of all past contingencies, must be derived not from •a perception of necessary relations or agreements, but from •some other source.

God has provided other means for giving us the knowledge of these things—means that are perfect for their purpose, and produce the effect they were intended to produce. But how they do this is beyond our skill to explain, I’m afraid. We know our own thoughts and the operations of our minds by a power we call ‘consciousness’. But this is only giving a name to this part of our make-up, not explaining its structure or showing how it produces in us an irresistible belief in its testimony. . . .

It is well known what subtle disputes went on all through the middle ages, and are still carried on, about God’s foreknowledge. Aristotle had taught that there can be no certain foreknowledge of contingent things; and in this he has been very generally followed, apparently just on the grounds that we •can’t conceive how such things should be foreknown and therefore •conclude foreknowledge to be impossible. This has given rise to an opposition and supposed inconsistency between God’s foreknowledge and human liberty. Some have given up foreknowledge in order to preserve liberty, others have given up liberty in order to preserve God’s foreknowledge.

It is remarkable that the parties to this dispute have never seen any difficulty in reconciling •liberty with the •knowledge of what is past. It is only foreknowledge and not memory that they have seen as hostile to liberty and hard to make consistent with it.

Yet I believe there is exactly as much difficulty about the past as about the future. I admit that we cannot account for

•foreknowledge of the actions of a free agent,

but I maintain that we are no better able to account for

•memory of the past actions of a free agent.

If you think you can prove that the actions of a free agent can’t be foreknown, you will find that those same arguments have just as much force to prove that the past actions of a free agent can’t be remembered. It is true that •what is past did certainly exist. It is no less true that •what is future will certainly exist. I don’t know any reasoning—from the constitution of the agent or from his circumstances—that doesn’t apply just as strongly to his past as to his future actions. The past was but now is not. The future will be but now is not. The present is equally connected or unconnected with both.

Why have men seen cases that are in fact perfectly alike as being so different? I think it is for this reason: The faculty of memory in ourselves convinces us, from fact, that it is possible for a thinking being—even a finite being—to have certain knowledge of past actions of free agents, without tracing them from anything necessarily connected with them. But having in ourselves no foreknowledge corresponding to our memory of what is past, we find great difficulty in admitting it to be possible even for God.

When we have a faculty in some degree, we easily admit that God can have it in a more perfect degree; but we hardly allow to be possible—·even for God·—a faculty that has nothing corresponding to it in our constitution. We are so constituted as to have an intuitive knowledge of many past things, but we have no intuitive knowledge of the future. Perhaps we could have been so constituted that we had intuitive knowledge of the future but not of the past; and that constitution wouldn’t have been any harder to explain than our actual one is, though it might be much more inconvenient! If that had been how we were built, we would have found no difficulty in accepting that God can know all future things, but much difficulty in accepting his knowledge of things that are past.

None of our original faculties can be explained. Memory is one of them. Only ·God· who made our faculties fully comprehends •how they are made and •how they produce in us not only a conception of but a firm belief in things that we need to know.

Chapter 3: Duration

From the principles laid down in chapter 1, I think it appears that our notion of duration—·of time passing, of periods of time·—as well as our belief in it comes to us through the faculty of memory. It is essential to anything that is remembered that it be something that is past, and we can’t think of something as past without thinking of some duration, large or small, between it and the present. So as soon as we remember something we must have both a notion of and a belief in duration. It is necessarily suggested by every operation of our memory, which is the faculty to which it ought to be ascribed. So this ·Essay on memory· is a proper place to consider what is known about it.

•Duration, •extension, and •number are the measures of all things that can be measured. When we apply them to finite things that we measure by them—·e.g. saying ‘The lecture lasted for an hour’, ‘The boot-laces are 60 inches long’, ‘There are five people in the room·’—they seem to be more clearly conceived and more within our grasp than anything else whatsoever.

•Extension has three dimensions, which gives it an endless variety of modifications [= ‘special cases’, ‘specific ways of being extended’] that can be precisely defined; and their various relations provide the human mind with its richest field of demonstrative reasoning, ·namely geometry·.

•Duration, having only one dimension, has fewer modifications; but these are clearly understood, and their relations admit of measure, proportion, and demonstrative reasoning.

•Number is called ‘discrete’ quantity, because it is made up of units that are all equal and similar, and it can only be divided into units. (This is true in some sense even of fractions < 1, which these days are also commonly called ‘numbers’. For in every such fractional number, one is supposed to be subdivided into a certain number of equal parts which are the units for that fraction and for all fractions with the same denominator.) Duration and extension are not •discrete but •continuous quantity. Their parts are perfectly alike but divisible without end.

When thinking about the size and proportions of the various intervals of •duration, we find a need to give a name to some known portion of it, such as an hour, a day, a year. Treating these as units, we can form a clear conception of some longer period of time by thinking of how many of these units it contains. And we find that we need a similar procedure to have clear conceptions of the sizes and proportions of extended things. Thus •number is necessary as a common measure of •extension and of •duration.

But it can be that we have this need only because of the weakness of our understanding. The mathematicians have been clever enough to discover that this device—·this measuring of things in terms of numbers of units·—won’t always serve our purpose. For there are proportions of continuous quantity that can’t be exactly expressed by numbers. For example (and there are many others), there is no numerically exact answer to the question ‘What proportion of the length of a square’s diagonal is the length of its side?’

Periods of time have the relations of before and after to •other periods, and the relations past and future to •the present. The notion of •past is immediately suggested by memory, as I have remarked; and when we have acquired the notions of •present and •past, and of •before and •after, we can out of these construct a notion of the •future—namely the period that is after the present. Nearness and distance are relations equally applicable to time and to place. Distance in time is •intrinsically so different from distance in place, and yet so like it in its •relational properties, that it’s hard to decide whether the word ‘distance’ is applied to both in the same sense or only analogically.

space: The extension of bodies that we perceive by our senses leads us necessarily to the conception of and belief in. . .

time: The duration of events that we remember leads us necessarily to the conception of and belief in. . .

space: . . . a •space that remains immovable when the body is moved.

time: . . . a •duration that would have gone on uniformly even if the event had never happened.

space: Without space there can be nothing that is extended.

time: Without time there can be nothing that has duration.

This I think undeniable, ·and it makes the properties extension and duration fairly clear and easy to understand·. But that clarity and ease is matched by the darkness and difficulty of thinking about ·the individuals· space and time. Because there must be space wherever there is or can be something extended, and there must be time whenever there is or can be something that has duration, we can’t even imagine limits to space and time. They defy all limitation. Space swells in our conception to •immensity, time swells to •eternity.

We can’t grasp a past eternity; ·but we can’t dodge the notion of a past eternity by supposing that time began, because· unless we take the phrase ‘a beginning of time’ in a figurative sense, it expresses a contradiction. By a common figure of speech we give the name ‘time’ to the motions and revolutions by which we measure time—e.g. days and years. We can conceive a beginning of those perceptible measures of time, and say that there was a time when they didn’t exist, a time not variegated by any motion or change; but to say that there was a time before all time is a contradiction.

All limited duration is included within time, and all limited extension within space. Time and space contain all finite existences in their capacious womb, but aren’t themselves contained by anything. Created things have their particular place in space and their particular place in time; but time exists throughout all of space, and space exists at all times. They embrace each the other, and have that mysterious union that the schoolmen conceived between soul and body: the whole of each is in every part of the other—·at any split second the whole of space exists, and every cubic millimetre of space exists throughout the whole of time·. We don’t know what category or class of things we ought to put them into. They are not beings but rather the receptacles for every created being, receptacles without which no created being could possibly have existed. Philosophers have tried to put all the objects of human thought into these three classes: •substances, •properties, and •relations. Which of these should hold time, space, and number, the most common objects of thought?

[Then a paragraph about views of Newton and Clarke, relating the immensity of space and eternity of time to the unlimited nature of God. Reid hints that these are ‘the wanderings of imagination in a region beyond the limits of human understanding’.]

The schoolmen said that eternity is a nunc stans, that is a moment of time that stands still. This was to put a spoke into the wheel of time [= ‘to jam the wheel so that it stops turning’], and might give satisfaction to those who are to be satisfied by words without meaning. But I can as easily believe a circle to be a square as time to stand still.

Such paradoxes and riddles, if I may call them that, are what men get pulled into when they reason about time and space and try to understand their nature. Space and time are probably things of which the human faculties give an imperfect and inadequate conception. Hence difficulties arise that we uselessly try to overcome, and doubts arise that we can’t lay to rest. How are we to remove the darkness that hangs over space and time and makes us so apt to bewilder ourselves when we reason about them? It may need some faculty that we don’t have.

Chapter 4: Identity

Everyone has a conviction of his own identity as far back as his memory reaches; this conviction doesn’t need help from philosophy to strengthen it, and no philosophy can weaken it without first producing some degree of insanity.

The philosopher, however, may very properly regard this conviction as a fact about human nature that is worth attending to. If he can discover its cause, that will add something to his stock of knowledge. If not, ·i.e. if no-one can discover its cause·, the conviction of one’s own identity must be regarded as either •a part of our original constitution or •something produced by that constitution in a manner unknown to us.

First point: this conviction ·of one’s own identity· is utterly necessary for all exercise of reason. The operations of reason—whether practical reasoning about what to do or speculative reasoning in the building up of a theory—are made up of successive parts. In any reasoning that I perform, the early parts are the foundation of the later ones, and if I didn’t have the conviction that the early parts are propositions that I have approved or written down, I would have no reason to proceed to the later parts in any theoretical or practical project whatever.

I can’t remember a past event without being sure that I existed at the time remembered. There may be good arguments to convince me that I existed before the earliest thing I can remember; but to suppose that my memory reaches a moment further back than my belief in my own existence is a contradiction.

The moment a man loses this conviction,. . . .past things are done away with, and in his own belief that is the moment when he begins to exist. Whatever was thought or said or done or undergone before that period may belong to some other person; but he can never attribute it to himself, or act in any way that supposes it to be his doing.

That clearly shows us that we must have the conviction of our own continued existence and identity as soon as we are capable of thinking or doing anything on account of what we have thought or done or undergone before—i.e. as soon as we are reasonable creatures.

Let us consider •what is meant by ‘identity’ in general, •what is meant by ‘our own personal identity’, and •how we are led into the irresistible belief and conviction that everyone has of his own personal identity as far as his memory reaches. These are appropriate things to look into if we want to form as clear a notion as we can of this phenomenon of the human mind.

Identity in general I take to be a relation between a thing known to exist at one time and a thing known to have existed at another time. If you ask whether they are one and the same or two different things—·for example, ‘Is the professor who persuaded you to take the course the one who gave you an F in it?’·—everyone of common sense understands perfectly what your question means. So we can be certain that everyone of common sense has a clear and distinct notion of identity.

If you ask for a definition of identity, I confess that I can’t give one; it is too simple a notion to admit of logical definition. [For Reid’s linking of ‘logical definition’ to simplicity, see the first two pages of Essay 1, chapter 1.] I can say that it is a relation, but I can’t find words in which to say what marks identity off from other relations, though I’m in no danger of confusing it with any other! I can say that diversity is a contrary relation, and that similarity and dissimilarity are another pair of contrary relations, which everyone easily distinguishes, conceptually, from identity and diversity.

I see evidently that identity requires an uninterrupted continuance of existence. Something that stops existing can’t be the same thing as something that begins to exist at a later time; for this would be to suppose that

•a thing existed after it had stopped existing, and

•existed before it was produced,

and these are both manifest contradictions. Continued uninterrupted existence is therefore necessarily implied in identity.

From this we can infer that identity can’t properly be applied to our pains, our pleasures, our thoughts, or any operation of our minds. The pain I feel today is not the same individual pain that I felt yesterday, though they may be similar in kind and degree, and may have the same cause. This holds for every feeling and for every mental operation. They are all successive in their nature, like time itself, no two moments of which can be the same moment.

It’s not like that with the parts of absolute space. They always are, were, and will be the same. Up to this point I think we are on safe ground in our moves towards fixing the notion of identity in general.

It is perhaps harder to ascertain precisely the meaning of personhood, but for the present topic we don’t need to. For our present purpose, all that matters is that all mankind place their personhood in something that can’t be divided or consist of parts. A part of a person is an obvious absurdity.

When a man loses his estate, his health, his strength, he is still the same person and has lost nothing of his personhood—·i.e. he is just as much a person as he was before·. If he has a leg or an arm cut off, he is the same person that he was before. The amputated limb is no part of his person; if it were, it would have a right to a part of his estate, and be liable for a part of his debts! It would be entitled to a share of his merit and demerit—which is plainly absurd. A person is something indivisible; it is what Leibniz called a ‘monad’.

My personal identity, therefore, implies the continued existence of that indivisible thing that I call myself. Whatever this self may be, it is something that thinks and wonders what to do and decides and acts and is acted on. I am not thought; I am not action; I am not feeling; I am something that thinks and acts and feels. My thoughts and actions and feelings change every moment; rather than lasting through time they occur in a series; but the self or I to which they belong is permanent, and relates in exactly the same way to all the successive thoughts, actions, and feelings that I call mine. These are the notions that I have of my personal identity. You may want to object:

All this may be imagined, not real. How do you know—what evidence do you have—that there is such a permanent self that has a claim to all the thoughts, actions, and feelings that you call yours?

I answer that the proper evidence I have of all this is remembering. I remember that twenty years ago I had a conversation with Dr Stewart; I remember several things that happened in that conversation; my memory testifies not only that this was done but that it was done by me who now remember it. If it was done by me, I must have existed at that time, and continued to exist from then until now. If the very same person that I call myself didn’t have a part in that conversation, my memory is deceptive—it gives clear and positive testimony of something that isn’t true. Everyone in his right mind believes what he clearly remembers, and everything he remembers convinces him that he existed at the time remembered.

Although •memory gives the most irresistible evidence of my being the same person who did such-and-such a thing at such-and-such a time, I may have •other good evidence of things that happened to me and that I don’t remember. I know who gave birth to me and fed me at her breast, but I don’t remember these events.

What makes it the case that I was the person who did such-and-such is not my remembering doing it. My remembering doing it makes me know for sure that I did it; but I could have done it without remembering it. The relation to me that is expressed by saying ‘I did it’ would be the same even if I hadn’t the least memory of doing it. This thesis:

•My remembering that I did such-and-such—or, as some choose to express it, my being ‘conscious that’ I did it—makes it the case that •I did do it

seems to me as great an absurdity as this:

•My believing that the world was created makes it the case that •it was created!

The point I’m making in this paragraph would have been unnecessary if some great philosophers hadn’t contradicted it.

When we pass judgment on the identity of people other than ourselves, we go by other evidence and decide on the basis of various factors that sometimes produce the firmest assurance and sometimes leave room for doubt. The identity of persons has often been the subject of serious litigation in courts of law. But no-one in his right mind ever had doubts about his own identity as far as he clearly remembered.

The identity of a person is a perfect identity: wherever it is real, it doesn’t admit of degrees—it is impossible that a person should be partly the same and partly different, because a person is a monad [Reid’s word] and isn’t divisible into parts. Our evidence for the identity of other people does indeed admit of all degrees: we can be absolutely certain ·that this is Martin Guerre· or think there is just a faint chance ·that this is Martin Guerre·, or anything in between those extremes. But still it is true that the same person is perfectly the same, and can’t be partly the same or fairly much the same. . . .

We probably at first derive our notion of identity from the natural conviction that everyone has had, from the dawn of reason, of his own identity and continued existence. The •operations of our minds are all successive, and have no continued existence. But the •thinking being has a continuous existence, and we have an irresistible belief that it remains the same through all the changes in its thoughts and operations.

Our judgments about the identity of objects of sense seem to be based on much the same kind of evidence as our judgments about the identity of other people.

Wherever we observe great •similarity we are apt to presume •identity, if no reason appears to the contrary. When two objects are perceived at the same time, they can’t be one object, however alike they may be. But if they are presented to our senses at different times, we are apt to think them the same, merely because of their similarity.

Whether this is a natural prejudice, or whatever its cause is, it certainly appears in children from infancy; and when we grow up it is confirmed in most instances by experience. For we rarely find two individuals of the same species that are not distinguishable by obvious differences.

When a man challenges a thief whom he finds in possession of his watch, he goes purely by similarity—·’This looks like my watch’·. When the watchmaker swears that he sold that watch to this person, his testimony is based on similarity. The testimony of witnesses to the identity of a person is commonly grounded on no evidence except similarity.

Thus it appears that •the evidence we have of our own identity as far back as we remember is of a totally different kind from •the evidence we have for the identity of other persons or of perceptible objects. The •former is based on memory, and gives undoubted certainty. The •latter is based on similarity and on other facts that are often not so decisive as to leave no room for doubt.

The identity of perceptible objects is never perfect. All bodies have countless parts that can be separated from them by various causes; so they are subject to continual changes of their substance—increasing, diminishing, changing insensibly ·by gaining or losing very small parts·. When something alters thus gradually, it keeps the same name (because language couldn’t afford a different name for every different state of such a changing being) and is considered as the same thing. Thus we see an old regiment marching past and we say that it fought at Poitiers a century ago, although no-one now alive belonged to it then. We say a tree is the same in the seed-bed and in the forest. A warship that has successively changed its tackle, sails, masts, planks, and timbers, while keeping the same name, is the same.

Thus, the identity that we ascribe to bodies—whether natural or artificial—isn’t perfect identity; it is rather something which for convenience of speech we call identity. It admits of a great change of the subject, as long as the change is gradual, and sometimes even a total change. ·For example, we might say ‘This is the ship that turned the tide of battle off Cadiz in 1645’, although every part of the ship had been replaced, a little at a time·. How do the changes that ordinary language allows as consistent with •identity differ from those that are thought to destroy •it? They don’t differ in kind, but only in number and degree. ·For example, it might fail to count as ‘the same ship’ because the total turn-over of planks, masts etc. happened too quickly—which is a matter of degree, not of kind·. Identity has no fixed nature when applied to •bodies; and questions about the identity of a body are very often questions about words. But identity when applied to •persons has no ambiguity and doesn’t admit of degrees, or of more and less. It is the basis for all rights and obligations, and for all accountability, and the notion of it is fixed and precise.

Chapter 5: Locke’s account of the origin of our ideas, especially the idea of duration

It was a very laudable attempt of Locke’s ‘to enquire into the origins of those ideas, notions, or whatever you please to call them, that a man observes and is conscious of having in his mind, and into how the understanding comes to be furnished with them’. No man was better qualified for this investigation, and no man, I think, ever engaged in it with a more sincere love of truth.

He had considerable success in this, but I think he’d have had even more if he hadn’t too early formed a system or hypothesis on this subject, without all the caution and patient induction that is necessary in drawing general conclusions from facts.

The sum of his doctrine I take to be this:

All our ideas or notions fall into one of two classes, the simple and the complex. The simple ones are purely the work of Nature, the understanding being merely passive in receiving them. They are all suggested by two powers of the mind, namely sensation and reflection; and they are the materials of all our knowledge. Complex ideas are formed by the understanding itself; once it has been stocked with simple ideas of sensation and reflection, the understanding has the power to repeat, compare, and combine them. . . .and so can at its pleasure make new complex ideas. But it isn’t within the power of the most exalted intellect wit or enlarged understanding, by any quick-wittedness or variety of thought, to invent or create one new simple idea that didn’t get into the mind by sensation or reflection. Just as

•our only power over the material world is a power to compound, divide, and assemble in various forms the matter that God has made, and doesn’t enable us to produce or annihilate a single atom,

so also

•we can compound, compare and abstract the original and simple ideas that Nature has given us, but can’t make in our minds any simple idea not received by our senses from external objects or by reflection from the operations of our own mind.

(Adapted by Reid from Essay II.ii.1-2)

This account of the origin of all our ideas was adopted by Berkeley and Hume; but some very able philosophers who hold Locke’s Essay in high esteem are dissatisfied with it.

Hutcheson in his Enquiry into the Origin of our Ideas of Beauty and Virtue has tried to show that these—·i.e. the ideas of beauty and of virtue·—are original and simple ideas ·that don’t come from sensation or reflection, and are instead· furnished by original powers ·of the mind·, which he calls the sense of beauty and the moral sense.

Price in his Review of the Principal Questions in Morals has rightly observed that if we take the words ‘sensation’ and ‘reflection’ as Locke defined them at the start of his excellent Essay, it will be impossible to derive some of our most important ideas from them; and that many simple and original notions are provided for us by the understanding, i.e. by our judging and reasoning power.

Locke says that by ‘reflection’ he means ‘the notice that the mind takes of its own operations and the manner of them’. This, I think, is what we ordinarily call ‘consciousness’; and we do indeed derive from it our notions of the operations of our own minds. Locke often speaks of the operations of our own minds as the only objects of reflection.

When ‘reflection’ is taken in this restricted sense, to say that •all our ideas are ideas either of sensation or reflection is to say that •everything we can conceive is either some object of sense or some operation of our own minds—and that is far from being true.

But ‘reflection’ is commonly used in a much broader sense; many operations of the mind are better candidates for the label ‘reflection’ than consciousness is. We reflect when we remember or call to mind some past event or state of affairs and survey it with attention. We reflect when we define, when we distinguish, when we judge, when we reason, whether about material things or intellectual ones.

When reflection is taken in this ·broader· sense, which is more common and therefore more proper than the sense Locke gives the word, it can rightly be said to be the only source of all our clear and precise notions of things. For although our first notions of material things are acquired by the external senses, and our first notions of the operations of our own minds by consciousness, these first notions are neither simple nor clear. Our senses and our consciousness are continually shifting from one object to another; their operations are transient and momentary, and leave no clear notion of their objects until they are recalled by memory, examined with attention, and compared with other things.

This reflection—·i.e. ‘reflection’ in the broad sense·—is not one power of the mind; it involves many powers, such as recollecting, attending, distinguishing, comparing, judging. By these powers our minds are provided not only with many simple and original notions, but with all our notions that are precise and well-defined—these being the only proper materials of reasoning. Many of these are not notions of perceptible objects or of the operations of our own minds, so they are not ideas of sensation, or of reflection in Locke’s sense of ‘reflection’. But if you want to call them ‘ideas of reflection’, taking that word in the more common and proper sense, I have no objection.

Locke seems to me to have sometimes •used ‘reflection’ in the limited sense given to it in his definition and sometimes •slid unawares into the common sense of the word; and by this ambiguity his account of the origin of our ideas is made obscure and tangled.

After these remarks about Locke’s general theory of the origin of our ideas or notions, I proceed to some observations on his account of the idea of duration.

He says: ‘Reflection on the sequence of ideas that appear one after another in our minds is what provides us with the idea of succession; and the distance between any two parts of that succession is what we call “duration”.’ (Essay II.xiv.3)

If he means that the idea of succession is prior to the idea of duration—whether prior time or prior in the order of Nature—I think this is impossible, for a reason given by Price: succession presupposes duration, so that it can’t in any sense be ‘prior’ to it; so it would be more proper to derive the idea of succession from that of duration ·than vice versa·. [’x is prior in time to y’ just means that x occurs before y does. ‘x is prior in the order of Nature’ means that any definition or analysis or explanation of y would have to involve x, and not vice versa.]

How does Locke say we get the idea of succession? We get it, he says, by reflecting on the sequence of ideas that appear one after another in our minds.

‘Reflecting on the sequence of ideas’—that has to mean remembering the sequence and attending to what our memory testifies concerning it; for if we didn’t remember it we couldn’t have a thought about it. So it’s evident that this reflection includes memory, without which there couldn’t be any reflection on what is past or, therefore, any idea of succession.

Speaking strictly and philosophically, no kind of succession can be an object of the senses or of consciousness. You can only sense what is the case now; you can only be conscious of what is the case now; and now—a point in time—can’t contain a succession. Therefore, the motion of a body—a successive change of place—couldn’t be observed by the senses alone without the aid of memory.

This observation seems to contradict the common sense and common language of mankind, when they affirm that they ‘see a body move’, thus holding motion to be an object of the senses. [Reid then, at considerable length, explains this away: it comes, he says, from the fact that the vulgar use the present tense and the word ‘present’ to signify a period of time, and not always a very short one; whereas he has been using ‘present’ in the philosophers’ sense in which it stands for ‘that indivisible point of time which divides the future from the past’. The vulgar usage is all right for everyday purposes, he says, but his point—expressed in the philosophical sense of ‘present’ or ‘now’—still stands. Then:]

Having considered Locke’s account of the idea of succession, let us next consider how he derives the idea of duration from the idea of succession. He writes: ‘The distance between any parts of that succession, or between the appearance of any two ideas in our minds, is what we call duration.’(II.xiv.3)

To get a firmer hold on this, let us call the ·temporal· distance between one idea and its immediate successor one element of duration; the distance between an idea and the next idea but one in the sequence two elements of duration, and so on. If •ten such elements have duration, then •one element must also have duration, for otherwise duration would be made up of parts with no duration, which is impossible. . . . Indeed, nothing is more certain than that every elementary part of duration must have duration, just as every elementary part of extension must have extension.

But now see where we have come to: there is •no succession of ideas within these elements of duration, or single intervals of successive ideas; but we must think of them as having •duration! From this we can infer with certainty that we have a concept of duration that doesn’t involve any succession of ideas in the mind.

We can •measure duration by the succession of thoughts in the mind, as we measure length by inches or feet; but the •notion or idea of duration must be antecedent to the measuring of it, just as the notion of length is antecedent to the length’s being measured.

Locke draws some conclusions from his account of the idea of duration; we may use these as a way of checking on whether the account is right. One conclusion is that if it were possible for a waking man to keep only one idea in his mind, without variation, he would have no perception of duration at all; and the moment when he began to have this idea would seem to have no ·temporal· distance from the moment when he stopped having it.

·This can’t be right·. That one idea should seem to have no duration, and that a multiplication of this no-duration should seem to have duration, strikes me as being just as impossible as that the multiplication of nothing should produce something.

Another conclusion that Locke draws from this theory is that the same period of duration appears long to us if the succession of ideas in our mind is quick, and short if the succession is slow.

There can be no doubt that the same length of duration appears in some circumstances much longer than in others; the time appears long when a man is suffering pain or distress and when he is eager in the expectation of some happiness. On the other hand, when he is pleased and happy in pleasant conversation, or delighted with a variety of pleasant objects that strike his senses or his imagination, time flies away and appears short.

According to Locke’s theory, in the time-seems-long case the succession of ideas is very quick, and in the time-seems-short case it is very slow. I’m inclined to think that the exact opposite is the truth! When a man is racked with pain or with expectation, he can hardly think of anything but his distress; and the more his mind is occupied by that single object, the longer the time seems. On the other hand, when he is entertained with cheerful music, with lively conversation and brisk sallies of wit, there seems to be the quickest succession of ideas but the time seems shortest. . . .

If the idea of duration were acquired merely from the succession of ideas in our minds, that succession itself must seem to us equally quick at all times, because the only measure of duration is the number of succeeding ideas; but if you are capable of reflection at all, I’m sure you are aware that at some times your thoughts come slowly and heavily and at other times have a much quicker and livelier motion.

I know of no ideas or notions that have a better claim to be accounted simple and original than those of space and time. [The recurring phrase ‘simple and original’ is a weapon of Reid’s against Locke. An ‘original’ notion or idea is one that starts in the mind rather than being put into it from the outside by sensation. And a ‘simple’ idea or notion can’t have been put together in the mind by the kind of compounding operation that Locke allows. So any idea that is both original and simple is a counter-example to Locke’s theory about the origin of our ideas. What place do ‘ideas of reflection’ have in this line of thought? It’s not clear. Some such ideas are •simple and all are •original in the sense that they start in the mind rather than being put into it from outside. Reid doesn’t directly attack that problem.] It is essential to both space and time to be made up of parts, but every part is similar to the whole and of the same nature. Because space has three dimensions, different parts of it can differ in shape as well as in size; but time has only one dimension, so its parts can differ from it only in size; and as it is one of the simplest objects of thought, our conception of it ·can’t come from our forming it by composition in Locke’s manner, so it· must be purely the effect of our constitution, and given to us by some original power of the mind.

The sense of seeing, by itself, gives us the conception of and belief in only •two dimensions of extension, but the sense of touch reveals •three; and from thinking about finite extended things we are necessarily led by reason to the belief in an immensity—·a space infinite in all directions·—that contains them.

When we consider •the smallest parts of time and space, our understanding is just as puzzled as it is when we consider •the whole. We are forced to acknowledge that space and time are in their nature divisible without end or limit; but there are limits beyond which our faculties can’t divide either of them.

[Reid then spends a page discussing empirical questions about how finely humans can discriminate small lengths of space or time. He ends with an experiment which he says shows ‘that the sixtieth part of a second of time is discernible by the human mind’.]

Chapter 6: Locke’s account of our personal identity

In a chapter on identity and diversity, Locke makes many ingenious and sound observations, and some that I think can’t be defended. I shall confine my discussion to his account of our own personal identity. His doctrine on this subject has been criticized by Butler in a short essay appended to his The Analogy of Religion, an essay with which I complete agree.

As I remarked in chapter 4, identity presupposes the continued existence of the being whose identity is affirmed, and therefore it can be applied only to things that have a continuous existence. For as long as any being continues to exist, it is the same being; but two beings that have different beginnings or different endings of their existence can’t possibly be the same. I think Locke agrees with this.

He is absolutely right in his thesis that to know what is meant by ‘same person’ we must consider what ‘person’ stands for. He defines ‘person’ as a thinking being endowed with reason and with consciousness—and he thinks that consciousness is inseparable from thought.

From this definition it follows that while the thinking being continues to exist, and continues thinking, it must be the same person. To say that

•the thinking being is the person,

and yet that

•the person ceases to exist while the thinking being continues,

or that

•the person continues while the thinking being ceases to exist,

strikes me as a manifest contradiction.

One would think that the definition of ‘person’ would completely settle the question of what the nature of personal identity is, or what personal identity consists in, though there might still remain a question about how we come to know and be assured of our personal identity. But Locke tells us:

Personal identity, i.e. the sameness of a rational being, consists in consciousness alone; and as far as this consciousness can be extended backwards to any past action or thought, so far reaches the identity of that person. So that whatever has the consciousness of present and past actions is the same person to whom they belong. [Adapted by Reid from II.xxvii.9; the main difference is that Locke wrote ‘is the same self’ etc.]

This doctrine has some strange consequences that the author was aware of. For example: if the same consciousness could be transferred from one thinking being to another (which Locke thinks we can’t show to be impossible), then two or twenty thinking beings could be the same person. And if a thinking being were to lose the consciousness of the actions he had done (which surely is possible), then he is not the person who performed those actions; so that one thinking being could be two or twenty different persons if he lost the consciousness of his former actions two or twenty times.

Another consequence of this doctrine (which follows just as necessarily, though Locke probably didn’t see it) is this: A man may be and at the same time not be the person that performed a particular action. Suppose that a brave officer

•was beaten when a boy at school, for robbing an orchard,

•captures an enemy standard in his first battle, and

•is made a general in advanced life.

Suppose also (and you have to agree that this is possible) that when he took the standard he was conscious of his having been beaten at school, and that when he became a general he was conscious of his taking the standard but had absolutely lost the consciousness of his beating.

Given these suppositions, it follows from Locke’s doctrine that he who was beaten at school is the same person who captured the standard, and that he who captured the standard is the same person who was made a general. From which it follows—if there is any truth in logic!—that

•the general is the same person as him who was beaten at school.

But the general’s consciousness does not reach so far back as his beating, and therefore according to Locke’s doctrine

•the general is not the person who was beaten.

So the general is and at the same time is not the person who was beaten at school.

Leaving the consequences of this doctrine to those who have leisure to trace them, I shall offer four observations on the doctrine itself.

[Before Reid does that, the preparer of these texts ventures to intrude as a commentator. Reid offers the foregoing argument so confidently, and to so much applause from others in later centuries, that its lack of charity towards Locke should be pointed out. The tone and tenor of Locke’s Identity chapter are compatible with this possibility:

(1) Locke was thinking in terms of sufficient conditions for personal identity.

(2) He silently assumed that elementary logic was to be built into his account, so that one sufficient condition for the truth of ‘x is z’ would be ‘x is y & y is z’.

(3) His ‘same consciousness’ account was meant to present not everything that could make a statement of personal identity true but everything that (a) could make such a statement true and (b) didn’t itself presuppose the truth of any such statement.

This interpretation would be ruled out only if he explicitly and persistently said that his ‘same consciousness’ stuff was meant, on its own, to give sufficient and necessary conditions for the truth of ‘x is z’. But he did no such thing. Why didn’t he say that elementary logic—i.e. the transitivity of identity—was being assumed? He shouldn’t have needed to; in a fair-minded world it would go without saying.]

(1) Locke attributes to consciousness the conviction we have of our past actions, as if a man could now be conscious of what he did twenty years ago. It is impossible to make sense of this unless ‘consciousness’ means memory, the only faculty by which we have an immediate knowledge of our past actions.

Sometimes in informal conversation a man says he is ‘conscious’ that he did such-and-such, meaning that he distinctly remembers that he did it. In ordinary everyday talk we don’t need to fix precisely the borderline between consciousness and memory. . . . But this ·imprecision· ought to be avoided in philosophy—otherwise we run together different powers of the mind, ascribing to one what really belongs to another. If a man can be ·strictly and literally· conscious of what he did twenty years or twenty minutes ago, then there is nothing for memory to do, and we oughtn’t to allow that there is any such faculty. The faculties of •consciousness and •memory are chiefly distinguished by this: •consciousness is an immediate knowledge of the present, •memory is an immediate knowledge of the past.

So Locke’s notion of personal identity, stated properly, is that personal identity consists in clear remembering. . . .

(2) In this doctrine, not only is •consciousness run together with •memory, but (even more strange) •personal identity is run together with •the evidence we have of our personal identity.

It is very true that my remembering that I did such-andsuch is the evidence I have that I am the identical person who did it. And I’m inclined to think that this what this is what Locke meant. But to say that my remembering that I did such-and-such, or my consciousness that I did it, makes me the person who did—that strikes me as an absurdity too crude to be entertained by anyone who attends to the meaning of it. For it credits memory or consciousness with having a strange magical power to produce its object, though that object must have existed before the memory or consciousness that ·supposedly· produced it.

Consciousness is the testimony of one faculty; memory is the testimony of another faculty. To say that •the testimony is the cause of •the thing testified is surely absurd if anything is absurd, and Locke couldn’t have said it if he hadn’t confused the testimony with the thing testified. . . .

(3) Isn’t it strange that the sameness or identity of a person should consist in something that is continually changing, and is never the same for two minutes?

Our consciousness, our memory, and every operation of the mind are still flowing like the water of a river, or like time itself. The consciousness I have this moment can’t be the same consciousness that I had a moment ago, any more than this moment can be that earlier moment. Identity can only be affirmed of things that have a continuous existence. Consciousness and every kind of thought is passing and momentary, and has no continuous existence; so if personal identity consisted in consciousness it would certainly follow that no •man is the same •person any two moments of his life; and as the right and justice of reward and punishment is based on personal identity, no man would be responsible for his actions! But though I take this to be the unavoidable consequence of Locke’s theory of personal identity, and though some people may have liked the doctrine the better on this account, I am far from imputing anything of this kind to Locke himself. He was too good a man not to have rejected in horror a doctrine that he thought would bring this consequence with it.

(4) In his discussion of personal identity, Locke uses many expressions that I find unintelligible unless he wasn’t distinguishing •the sameness or identity that we ascribe to an individual from •the identity which in everyday talk we ascribe to many individuals of the same species.

When we say that pain and pleasure, consciousness and memory, are the same in all men, this ‘same’ness can only mean similarity, i.e. sameness of kind. ·If it meant individual identity, i.e. identity properly and strictly so-called, it would be implying· that the pain of one man could be the same individual pain that another man also felt, and this is no more possible than that one man should be another man; the pain I felt yesterday can no more be the pain I feel to-day than yesterday can be today; and the same thing holds for •every operation of the mind and •every episode of the mind’s undergoing something. The same kind or species of operation may occur in different men or in the same man at different times, but it is impossible for the the same individual operation to occur in different men or in the same man at different times.

So when Locke speaks of ‘the same consciousness being continued through a succession of different substances’, of ‘repeating the idea of a past action with the same consciousness we had of it at the first’ and ‘the same consciousness extending to past and future actions’, these expressions are unintelligible to me unless he means not the same individual consciousness but a consciousness that is of the same kind.

If our personal identity consists in consciousness, given that consciousness can’t be •the same individually for any two moments but only •of the same kind, it would follow that we are not for any two moments the same individual persons but the same kind of persons.

As our consciousness sometimes ceases to exist—as can’t have two beginnings of existence; so our identity would in sound sleep—our personal identity must cease with it, be irrecoverably lost every time we stopped thinking, even if according to Locke’s theory. He allows that a single thing only for a moment.

Chapter 7: Theories about memory

The common theory of ideas—i.e. of images in the brain or in the mind of all the objects of thought—has been very generally used to account for the faculties of •memory and •imagination as well as •perception by the senses. . . .

The Aristotelian view about memory is expressed by Alexander Aphrodisiensis, one of the earliest Greek commentators on Aristotle, thus:

. . . .The operations of our senses in relation to perceptible objects makes an impression. . . .or picture in our original sensorium, this being a trace of the motion caused in us by the external object. When the external object is no longer present, the trace remains, and is preserved as a kind of image of the object, and because of this preservation it becomes the cause of our having memory. . . . [The sensorium is part of the brain.]

A passage from Alcinous, expounding Plato, shows the ancient Platonists and Aristotelians agreeing that:

When the form or type of things is imprinted on the mind by the sense-organs, and imprinted in such a way that it isn’t deleted by time but preserved firm and lasting, its preservation is called memory.

On this basis, Aristotle explains the shortness of memory in children by their brain’s being too moist and soft to keep impressions that are made on it. And the defect of memory in old men he explains by the hardness and rigidity of their brain, which stops it from receiving any durable impression.

This ancient theory of the cause of memory is defective in two respects. ·One could express them by saying that the theory fails both parts of Newton’s ‘first rule of philosophising·’ [see Essay 1, near the end of chapter 3]. (1) If the assigned cause really did exist, it would be far from explaining the phenomenon ·of memory·. (2) There is no evidence—not even a probability—that that cause exists.

(1) All the nerves terminate in the brain; and disorders and damage to the brain are found to affect our powers of perception even when the external sense-organ and the relevant nerve are sound. These two facts make it probable that in perception some impression is made on the brain, as well as on the sense-organ and the nerves. But we are totally ignorant of the nature of this impression on the brain. It can’t resemble the perceived object, and it doesn’t provide the faintest explanation for the sensation and perception that follow it. I have argued all this in Essay 2, and I’ll now take it for granted.

Well, then, if the impression on the brain is insufficient to explain the •perception of objects that are •present, it can’t have a better chance of explaining the •memory of things that are •past!

So that even if it were certain that the impressions made on the brain in perception remain as long as there is any memory of the object, all we could infer from this is that by the laws of Nature that impression is connected with the remembering of that object. We would still know nothing about how the impression contributes to this remembering, because it is impossible to discover how thought of any kind should be produced by an impression on the brain or on any part of the body.

It would be absurd to say that this impression, rather than being the cause of memory, is memory.

If a philosopher undertakes to explain the force of gunpowder in the discharge of a musket, and then solemnly tells us that the cause of this phenomenon is the pulling of the trigger, this wouldn’t make us much wiser! Well, we aren’t told any more about the cause of memory by being told that it is caused by a certain impression on the brain. . . .

(2) Another defect in this theory is that there’s no evidence making it even probable that the assigned cause does exist, i.e. that the impression made on the brain in perception does remain after the object is removed.

That impression, whatever its nature may be, is caused by the impression that the object makes on the sense-organ and on the nerve. Philosophers suppose, without any evidence, that when the object is removed and the impression on the sense-organ and nerve stops, the impression on the brain continues and is permanent—i.e. that when the cause is removed, the effect continues. The brain, surely, doesn’t look better fitted to retain an impression than the organ and the nerve are.

Another point: suppose that the impression on the brain does continues after its cause is removed—then its effects ought to continue while it continues, i.e. the sensation and perception should be as permanent as the impression on the brain that is supposed to be their cause. But here the philosopher makes a second supposition, with as little evidence as he has for the first assumption, and of a contrary nature to that one. That is, he assumes that while the cause remains, the effect ceases.

And if this second supposition is granted, there is need for a third, namely that the same cause that at first produced sensation and perception afterwards produces memory— though memory is an operation essentially different both from sensation and perception.

A fourth supposition must also be made, namely that although this cause is permanent, doesn’t produce its effect at all times—it must be like an inscription that is sometimes covered with rubbish and on other occasions made legible. For the memory of things is often interrupted for a long time, and circumstances bring to our recollection things we had long forgotten. And to top off my series of criticisms: many things are remembered that aren’t objects of the senses, couldn’t ever have been perceived by the senses, and so couldn’t make any impression on the brain by means of the senses.

Thus when philosophers have piled one supposition on another, as the giants piled up the mountains in order to climb to the heavens, nothing comes of it: memory remains inexplicable, and we don’t know how we remember things past any more than we know how we are conscious of the present.

But I should remark here that although impressions on the brain are no help in explaining memory, it’s very likely that in the human frame memory does depend on some proper state or condition of the brain. Although the contents of our memory aren’t—and couldn’t possibly be—in the least like any brain-state, still Nature may have subjected us to this law that a certain constitution or state of the brain is necessary for memory. Many well known facts lead us to conclude that this is really the case.

Careful empirical work might lead to the discovery of the right way to keep the brain in the state that is favourable to memory, and of remedying the brain disorders that hinder memory. This would be an outstanding medical advance; but even if it were made, it would give no help in understanding how one brain-state assists memory and another hurts it.

I know for sure that the impression made on my hand by the jab of a pin occasions acute pain. But can any philosopher show how this cause produces the effect? The nature of the impression is perfectly known, but that knowledge gives no help in understand how the impression affects the mind. And if we knew •the brain-state that causes memory as clearly as we know •the impression on my hand that causes pain, we still wouldn’t know anything about how that brain-state contributes to memory. For all we know to the contrary, we could have been so constituted that the jab of a pin in the hand, instead of causing pain, should cause a memory! And that constitution would be no more inexplicable than our actual constitution is.

The body and mind operate on each other according to fixed laws of Nature; and it is the business of a philosopher to discover those laws by observation and experiment. But when he has discovered them, he must settle for knowing them as facts whose cause is inscrutable to the human understanding.

When Locke and those who have followed him speak of impressions on the brain as the cause of memory, they are more cautious than the ancients in saying this, and say it only in passing. Their preferred view is that memory is caused rather by our retaining in our minds the ideas acquired by either sensation or reflection.

Locke says this can be done in two ways:

First, by keeping the idea for some time actually in view—this is called contemplation. Secondly, by the power to revive again in our minds the ideas which, after being imprinted, have disappeared or have been (as it were) laid out of sight; and this is memory, which is (as it were) the storehouse of our ideas. (Adapted by Reid from Essay II.x.1-2)

To explain this more clearly, Locke immediately adds the following remark:

But our ideas are nothing but actual perceptions in the mind, and cease to be anything when they are not perceived; so that this ‘storing of ideas in the repository of the memory’ really means only that the mind has a power in many cases to revive perceptions that it has once had, with attached to them the additional perception that it has had them before. It is in this sense that our ideas are said to be ‘in our memories’, when they are actually nowhere. It’s just that there is an ability in the mind to revive them again when it wants to, and (as it were) paint them on itself anew, though some with more and some with less difficulty, some more lively and others more obscurely. (II.x.2)

In this account of memory, the repeated use of the phrase ‘as it were’ leads one to think that the account is partly figurative; so we must try to distinguish the •figurative part from the part that is philosophical ·and therefore absolutely •literal·. The figurative part is addressed to the ·reader’s· imagination: it presents a picture of memory that needs to be seen from a proper distance and from a particular point of view. The literal part is addressed to the ·reader’s· understanding, and we should be able to view it from close up and subject it to a critical examination.

The analogy between memory and a repository, and between remembering and keeping, is obvious and is to be found in all languages, because it is very natural to express the operations of the mind by images taken from material things. But in philosophy we ought to draw aside the veil of imagery and view the mind’s operations naked.

So when we are told that memory is a ‘repository’ or ‘storehouse’ of ideas, in which they are ‘stored’ when not perceived and brought out again brought when they are needed, I take this to be popular and rhetorical ·and figurative·. For Locke tells us that when they are not perceived they ‘are nothing’ and are ‘nowhere’; so they can’t ·literally· be stored in a repository or retrieved from it.

But he also tells us that ‘this “storing of ideas in the repository of the memory” really means only that the mind has a power in many cases to revive perceptions that it has once had, with attached to them the additional perception that it has had them before’. I think we have to understand this literally and philosophically.

But it seems to me that when something has stopped being anything, it is as hard to ‘revive’ it as to ‘store’ it in—or bring it out of—a ‘repository’. Once a thing has been annihilated, it—the very same thing—can’t be produced again, though another thing like it may be produced. Locke in another place accepts that a single thing can’t have two beginnings of existence. . . . From this it follows that an ability to ‘revive’ our ideas or perceptions after they have ceased to exist can’t mean more than an ability to create new ideas or perceptions similar to those we had before.

They are said to be revived ‘with attached to them the additional perception that the mind has had them before’. This surely would be a deceptive perception, because an idea can’t have two beginnings of existence, and we can’t believe that it could. All we can believe is that we formerly had ideas or perceptions very like these ones though not identically the same. And in any case, one would think that for me to have a perception that this is the one I had before or this is like the one I had before—it doesn’t matter which—requires me to have a memory of the one I had before.

In explaining this ‘reviving’ of our perceptions, Locke also says that ‘the mind (as it were) paints them on itself anew’. There may be something figurative in this; but even allowing for that, the remark must imply that the mind in painting things that have ceased to exist must have a memory of what they were, since every painter must have a copy either in front of him or in his imagination and memory.

These remarks on Locke’s account of memory are intended to show that his system of ideas throws no light on this faculty, but rather tends to darken it. . . .

Everyone knows what memory is; everyone has a clear notion of it. But when Locke speaks of a power to revive in the mind ideas that were imprinted and then disappeared, or that have been (as it were) laid out of sight, one would hardly know it was memory he was describing if he hadn’t told us! There are other things that it seems to fit at least as well as it does memory:

I see the picture of a friend. I shut my eyes, or turn them another way, and the picture disappears or is (as it were) laid out of sight. I have a power to turn my eyes again towards the picture, and immediately the perception is revived.

Is this memory? Surely not! But it fits Locke’s account as well as memory itself can do.

I would point out that Locke uses the word ‘perception’ in too indefinite a way, as he does the word ‘idea’.

In his chapter on perception (Essay II.ix), he says that perception is the ‘first faculty of the mind exercised about our ideas’ [= ‘the mind’s most basic way of engaging with ideas’]. But here ·in Locke’s chapter on memory (Essay II.x)· we are told that ideas are ‘nothing but perceptions’. It strikes me as odd to say that

•perception is the first faculty of the mind exercised about our ideas,

and even more odd to say that

•ideas are the first faculty of the mind exercised about our ideas.

·Of course Locke doesn’t say about ideas anything as weird as that, but why not?· Why shouldn’t ideas be a faculty, as well as perception, if both are the same?

Memory is said to be a power to revive our perceptions. Doesn’t it follow from this that everything that can be remembered is a perception? If that is so, it will be difficult to find anything in Nature but perceptions!

Our ideas, Locke tells us, are ‘nothing but actual perceptions’; but in many places in the Essay he says that ideas are the objects of perception, and that the mind in all its thoughts and reasonings doesn’t—and can’t—have any immediate object other than its own ideas. Doesn’t this make it seem that Locke either

•regarded the operations of the mind as the same thing as the objects of those operations

or

•used ‘idea’ sometimes in one sense and sometimes in another, without warning us of the ambiguity and probably without being aware of it?

One of the doctrines in Hume’s philosophy is that there is no distinction between the operations of the mind and their objects. But I see no reason to attribute this opinion to Locke. Instead, I think that despite his great judgment and candour, his understanding was entangled by the ambiguity of ‘idea’ and that most of the defects of his Essay come from that.

Hume saw further into the consequences of the common system concerning ideas than any author had done before him. [The ‘common system’ is the ‘common theory’ discussed in Essay 2, chapter 8.] He saw the absurdity of making every object of thought double, splitting it into •a remote object that has a separate and permanent existence and an •immediate object called an ‘idea’ or ‘impression’ that is an image of the other and doesn’t exist except when we are conscious of it. According to this system, our only communication with the external world is through the internal world of ideas, which represents the external world to the mind.

He saw that we had to reject one of these worlds as a fiction, and the question was Which? On the one hand,

All mankind—learned and uneducated—had invented the existence of the external world, without any good reason.

On the other:

Philosophers had invented the internal world of ideas, so as to account for the mind’s communication with the external world.

Hume adopted the former of these two opinions, and exercised his reason and eloquence in support of it.

Berkeley had gone far enough along this road to reject the material world as fictitious, ·a mere invention·, but it was left to Hume to complete the system, thus:.

According to his system, the only things a man can know or conceive are impressions and ideas in his own mind. And these ideas are not representatives, as they were in the old system. There is nothing else in Nature, or anyway nothing within the reach of our faculties, for them to represent. What the vulgar call ‘the perception of an external object’ is nothing but a •strong impression on the mind. What we call ‘remembering a past event’ is nothing but a present impression or idea that is •weaker than that of perception. And what we call ‘imagination’ is a present idea that is •weaker than that of memory.

So as not to be unfair to him, I quote his words in his Treatise of Human Nature:

We find by experience that when an impression has been present to the mind, it re-appears there later as an idea; and it can do this in either of two ways: •when in its new appearance it retains a good deal of its first liveliness and is intermediate between an impression and an idea; or •when it entirely loses that liveliness and is a perfect idea. The faculty by which we repeat our impressions in the first manner is called the ‘memory’, and the other the ‘imagination’. (Treatise I.i.3)

I have ·three· comments to offer concerning this account of memory and imagination.

(1) What are we to understand here by ‘experience’? Hume says that we find all this ‘by experience’; and I don’t see how this ‘experience’ can be meant as anything but memory. I mean ‘memory’ in the common meaning of the word, not the ‘memory’ that Hume defines! In the vulgar way of looking at things, memory is an immediate knowledge of something past. Hume doesn’t admit that there is any such knowledge in the human mind. He maintains that memory is nothing but a present idea or impression. But in defining ‘memory’ as he understands it, he takes for granted the kind of memory that he rejects. For if we are to find ‘by experience’ that an impression, after appearing once to the mind, then appears a second and a third time with different degrees of strength and liveliness, we’ll need to have a memory—·in the vulgar sense of the word!·—of its first appearance that is clear enough for us to recognize it on its second and third appearances despite its having considerably changed.

All experience presupposes memory—there can’t be any such thing as experience unless we trust memory, either our own or someone else’s. So it seems from Hume’s account of this matter that he found himself to have •the kind of memory that he acknowledges and defines, by exercising •the kind of memory that he rejects.

(2) What do we find by experience or memory? Hume answers that we find ‘that when an impression has been present to the mind, it re-appears there later as an idea; and it can do this in either of two ways’. If experience informs us of this, it certainly deceives us, for the thing is impossible and Hume himself shows it to be so. Impressions and ideas are fleeting perishable things that don’t exist except when we are conscious of them. If an impression could make a second and a third appearance to the mind, it would have to have existed continuously throughout the intervals between these appearances, and Hume accepts that that is a gross absurdity. So it seems that we ‘find by experience’ something that is impossible. Our experience is deceiving us, making us believe contradictions.

You may want to reply on Hume’s behalf:

The ‘different appearances of the impression’ should be understood not literally but figuratively. The impression is treated like a person, and made to appear at different times and in different clothing, when all that is meant is that there are appearances

•first of an impression,

•then of something intermediate between an impression and an idea (we call it memory),

•then finally of a perfect idea (we call it imagination).

This figurative meaning fits best with the last sentence of the quoted passage, where we are told that memory and imagination are faculties whereby we ‘repeat our impressions’ in a more or less lively manner. To ‘repeat an impression’ is a figurative turn of speech which signifies making a new impression that is like the previous one.

If we clear Hume of the absurdity implied in the literal meaning, by understanding him in this figurative way, then his definitions of ‘memory’ and ‘imagination’—stripped of their figurative dress—come down to this: Memory is the faculty of making a weak impression, and imagination is the faculty of making a still weaker impression, after a corresponding strong one. These definitions of ‘memory’ and ‘imagination’ have two defects: (a) They convey no notion of the thing defined; and (b) They can be applied to things of a very different nature from those that are defined. . . .

(3) When Hume tells us that we have an ability to repeat our impressions in a more or less lively manner, this implies that •we are the causes of our ideas of memory and imagination; but this contradicts what he says shortly before that, when he maintains that •impressions are the cause of their corresponding ideas, supporting this by what he calls a ‘convincing argument’. The argument for this needs to be very convincing! If take the idea to be •a second appearance of the impression, then the impression is the cause of itself. And if the idea is ·the first appearance of· a new impression similar to the previous one, then the impression goes out of existence and then produces the idea. Such are the mysteries of Hume’s philosophy.

Notice that the common system’s doctrine that ideas are the only immediate objects of thought leads to scepticism about •memory as well as about •the objects of sense. And this holds true whether the ideas are placed in the mind or in the brain.

Ideas are said to be internal and present, having no existence except when they are in the mind. The objects of sense are external things that exist continuously. When it is maintained that ideas or phantasms are the only things we immediately perceive, how can we from their existence infer the existence of an external world corresponding to them?

This hard question seems not to have occurred to the Aristotelians. Descartes saw the difficulty, and tried to find arguments by which we might infer the existence of external objects from the existence of our phantasms or ideas. The same course was followed by Malebranche, Arnauld, and Locke; but Berkeley and Hume easily refuted all their arguments and demonstrated that there is no strength in them.

The system of ideas naturally generates the same difficulty with regard to memory. (The only reason why philosophers didn’t notice it is that they attend less to memory than to the senses.) Ideas are ·supposed to be· present things: how from my having a certain idea in my mind now can I infer that a certain event corresponding to it really happened ten or twenty years ago?. . . .

It seems not to have occurred to Locke or to Berkeley that their system has the same tendency to overturn the testimony of memory as to overturn the testimony of the senses. Hume saw further than both, and found this consequence of the system of ideas to fit perfectly with his aim of establishing universal scepticism. So his system is more consistent than theirs, and his conclusions agree better with the premises.

Even if we grant to Hume that our ideas of memory afford no solid reason for believing in the past existence of things that we remember, he still has to face this question: How does it come about that •perception and •memory are accompanied by belief, while bare •imagination is not? On his system this belief can’t be justified; but still it ought to be accounted for as a phenomenon of human nature.

He has done this giving us a new theory of belief in general—a theory that fits very well with the theory of ideas, seems to be a natural consequence of it, and at the same time reconciles perfect scepticism with all the belief that we find in human nature. [Reid is here being very sarcastic. He means that perfect scepticism is compatible with everything that people in general believe if we understand those beliefs as being the sort of thing that Hume says belief is.]

[This paragraph amplifies Reid’s text in ways that the small-dots apparatus can’t easily cope with. The use, here and hereafter, of ‘F’ as a dummy predicate attached to ‘idea’ replaces Reid’s talk of a ‘modification’ of ideas.] Well, then, what is this belief? The idea-theorist will have to say either that

•Having a belief is just having an idea, or that

•Having a belief is having an F idea,

for some suitable value of F. Now, we conceive many things that we don’t believe, so the account of belief must be of the second of these kinds, i.e. a belief must be an idea of a certain kind, an F idea for some F. When we believe in an object, our idea of it is the same as when we merely conceive it; the belief doesn’t add any new idea to the thought we are having. So what marks off belief from mere conception—i.e. the required value of F—must have to do not with what idea the person has in his mind but rather with how he has it in his mind. Listen to Hume:

All the perceptions of the mind are of two kinds, impressions and ideas, which differ from each other only in their different degrees of force and liveliness. Our ideas are copied from our impressions and represent them in every detail. When you want somehow to vary your idea of a particular object, all you can do is to make it more or less strong and lively. If you change it in any other way it will come to represent a different object or impression. (Similarly with colours. A particular shade of a colour can acquire a new degree of liveliness or brightness without any other variation; but if you produce any other change it is no longer the same shade or colour.) Therefore, as belief merely affects how we conceive any object, all it can do—·the only kind of variation that won’t change the subject, so to speak·—is to make our ideas stronger and livelier. So an opinion or belief can most accurately defined as: a lively idea related to or associated with a present impression. (Treatise I.iii.7)

This theory of belief is rich with consequences, which Hume traces with his usual acuteness and brings into the service of his system. Much of his system is indeed built on it, and is of itself sufficient to make a case for what he calls his hypothesis that •belief is strictly an act of the feeling part of our natures rather than of the thinking part’ (Treatise I.iv.1)

It is very difficult to examine this account of belief with as straight a face as Hume had when he proposed it. . . . There is surely no ·other· science in which able and versatile men have fallen into such gross absurdities as ·some of them do· in treating of the powers of the mind. I can’t help thinking that Hume’s account of the nature of belief, and of what distinguishes perception from memory and both of them from imagination, is as absurd as anything ever seriously maintained by any philosopher.

Believing that P—that’s a mental operation of which everyone is conscious, and everyone understands perfectly what belief is, though on account of its simplicity we can’t give a logical definition of it. If we compare it with the strength or liveliness of our ideas, or with any feature of ideas, they are so far from appearing to be one and the same that they haven’t the least similarity.

‘A strong belief differs from a weak belief only in degree’—I can easily grasp that; but as for ‘•Belief differs from •no-belief only in degree’—no-one who understands his own language could believe that. For it amounts to saying that •something and •nothing differ only in degree, or that nothing is a ·certain low· degree of something!

For every proposition that can be believed, there is a contrary proposition that can be believed, this belief being a contrary of the other. The ideas of both beliefs, according to Hume, are the same except for their different degrees of liveliness. That is: contraries differ only in degree! Thus, pleasure may be a degree of pain, and hatred a degree of love. But there’s no profit in tracing the absurdities that follow from Hume’s doctrine of belief, for none of them can be more absurd than the doctrine itself.

Everyone knows perfectly what it is to •see an object with his eyes, what it is to •remember a past event, and what it is to •conceive something that doesn’t exist. These ·three· are quite different operations of the mind, and everyone is as certain of this as he is that sound differs from colour and both differ from taste. ‘Sound and colour and taste differ only in degree’—I don’t find that any more incredible than ‘Seeing and remembering and imagining differ only in degree’.

Hume in the third Book of his Treatise of Human Nature is aware that his theory of belief is open to strong objections, and seems to retract it somewhat; but how far he retracts it is hard to say. He seems still to think that a belief is only an F idea but that ‘vivacious’ [replaced elsewhere in this version by ‘lively’] is not the right word to express what F stands for. Instead of ‘vivacious’ he uses some analogical phrases to explain F, such as ‘apprehending the idea more strongly or taking firmer hold of it’. [This refers to an item in an Appendix to Treatise I, first printed at the end of the volume that is mainly devoted to Treatise III.]

There is nothing more meritorious in a philosopher than to retract an error when he becomes convinced that it is an error; but in this instance I humbly think that Hume claims that merit without doing much to deserve it. For I can’t see that ‘apprehending an idea more strongly or taking firmer hold of it’ expresses any value of F other than what was earlier expressed by ‘strong’ and ‘vivacious’, or even that it expresses the same value more properly. Hume holds that

perception involves an F idea,

memory involves an F idea, and

imagination involves an F idea,

the differences consisting purely in different degrees of Fness. And this view is guilty of all the absurdities I have listed, no matter what he takes Fness to be—whether it is liveliness or something else that doesn’t even have a name.

Before leaving the subject of memory, I should remark on Aristotle’s distinction between •memory and •reminiscence, because it has a real basis in Nature although there is not, I think, any ordinary-language way of marking it.

Memory is a kind of habit; it isn’t always at work with regard to things we remember, but it is ready to suggest them when there is a need to do so. ·There are three degrees of this habit·:

•The most perfect degree: the ·remembered· thing presents itself to our remembrance spontaneously and without labour as often as there is occasion.

•Second best: the ·remembered· thing is forgotten for a period of time even when there is a need to remember it, but eventually some incident brings it to mind without any search.

•Third best: we cast about and search for what we want to remember, and at last find it.

The third of these is, I think, what Aristotle calls ‘reminiscence’ as distinguished from ‘memory’.

So reminiscence includes willing to recollect some past thing and searching for it. [Reid like most of his contemporaries thought that all voluntary action starts with an act of willing. It is something like actively wanting or setting oneself to do such-and-such.] It may be objected:

If we •will to remember something, we must have a conception of the thing we will to remember; we can’t •will something without conceiving of it. That being so, it seems that willing to remember something implies already remembering it, in which case there’s no need to search for it.

But this difficulty is easily removed. When we will to remember a thing, we must remember something relating to it that gives us a relative conception of it; but we may at the same time have no conception of what the thing is, only a conception of how it relates to something else. For example, I remember that a friend asked me to do something at the University library, and I forgotten what I was to do. By applying my thought to what I do remember concerning it—who made the request, and when and where and in what conversational context—I am led in a sequence of thought to the very thing I had forgotten, and thus I come to recollect clearly what it was that he asked me to do.

Aristotle says that brute animals don’t have reminiscence, and I think he is probably right. But he says that they do have memory. No doubt they have something very like memory, sometimes in a very high degree. A dog knows his master after long absence. A horse will, as accurately as a man, trace back a road he has once travelled; and what makes this especially strange is that the thought-sequence that the horse had when going one way must be reversed on his return. . . . Brutes certainly can learn much from experience, which seems to imply memory.

Yet I see no reason to think that brutes measure time as men do, by days, months, or years, or that they have any clear knowledge of •the interval between things that they remember, or of •their distance from the present moment. If we couldn’t record transactions according to their dates, human memory would be very different from what it is, and perhaps would be more like the memory of brutes.

Essay 4: Conception

Chapter 1: Conception (or simple apprehension) in general

Chapter 2: Theories about conception

Chapter 3: ·Four· mistakes about conception

Chapter 4: The train of thought in the mind

Chapter 1: Conception (or simple apprehension) in general

Conceiving, imagining, apprehending, understanding, having a notion of a thing, are common words used to express the operation of the understanding that the logicians call simple apprehension. In ordinary language the same thing is meant by ‘having an idea’ of a thing—a usage that I think has become current since Locke’s time.

Logicians define ‘simple apprehension’ to be the bare •conception of a thing without any •judgment or •belief about it. If this were intended as a strictly logical definition, one might object that ‘conception’ and ‘apprehension’ are synonyms, and that we may as well define ‘conception’ by ‘apprehension’ as vice versa. But it ought to be remembered that the simplest operations of the mind can’t be logically defined. To have a clear notion of them, we must attend to them as we feel them in our own minds. If you want a clear notion of scarlet, you’ll never get it from a definition; what you must do is to look at an example of scarlet and compare it with the colours that come nearest to it, observing the difference that marks off scarlet from the others—a difference that you still can’t possibly define.

Everyone is aware that he can conceive a thousand things about which he believes nothing at all—things such as a horse with wings, a mountain of gold—but although conception can occur without any degree of belief, even the smallest belief has to involve conception. Someone who believes must have some conception of what he believes.

Without trying to define this operation of the mind, I’ll try to explain some of its properties; ·in chapter 2· to consider the theories about it; and ·in chapter 3· to discuss mistakes that philosophers have made concerning it. ·The present chapter will expound nine properties of conception·.

(1) Conception enters as an ingredient in every operation of the mind. Our senses can’t give us a •belief in any object without giving some conception of it at the same time. No man can either •remember or •reason about things of which he has no conception. When we •will to engage in some physical activity, we must have some conception of what we will to do. There can’t be any •desire or •aversion, •love or •hatred, without some conception of the object. We can’t •feel pain without conceiving it, though we can conceive it without feeling it. All this is self-evident.

So there must be conception in every operation of the mind, everything we call ‘thought’. When we analyse the operations of the •understanding or of the •will we shall always find this at the bottom. . . .; but though there is no mental operation without conception, still conception can occur nakedly detached from all the rest, and then it is called ‘simple apprehension’ or the ‘bare conception’ of a thing.

[(a) Reid is here using ‘thought’ as a catch-all term for operations of the mind, a very broad sense of the term that became common after Descartes’s correspondingly broad sense for pensée and cogitatio. (b) For Reid the terms ‘will’ and ‘understanding’ between them divide up the entire life of the mind. His Essays on the Intellectual Powers of Man, from which the present work comes, are devoted to the understanding. Reid’s earlier Essays on the Active Powers of Man were concerned with the will.]

As all the operations of our mind are expressed by language, everyone knows that it is one thing (a) to understand what is said, to conceive or apprehend its meaning, whether it is a word, a sentence, or a whole speech; and it is another thing (b) to judge concerning it, to assent or dissent, to be persuaded or moved. (a) is simple apprehension, and can occur without (b); but (b) cannot occur without (a).

(2) In bare conception there can’t be either truth or falsehood, because conception neither affirms nor denies. Every judgment, and every proposition [= ‘sentence’] by which judgment is expressed, must be true or false; and truth and falsehood—using those terms in their proper sense—can belong to nothing but judgments or propositions that express judgments. . . .

[We often say such things as ‘He has a false conception of x’, Reid acknowledges, but he explains this away, saying that ‘we always find that when we speak of true or false conceptions, we mean true or false opinions’. He quotes a passage from Locke expressing the same view, on the assumption—Reid says—that Locke in this context is using ‘idea’ to mean ‘conception’. Then he shifts into something that he admits is a ‘digression’ from the supposed topic of this section. Thus:]

Incidentally, in this passage as in many others Locke uses the word ‘perception’ as well as ‘idea’ to signify what I call ‘conception’ or ‘simple apprehension’. And in his chapter on perception he uses it in the same sense. ‘Just as perception is the mind’s first way of engaging with ideas,’ he says, ‘·the idea of· it is the first and simplest idea we have from reflection. Some call it thinking’ (Essay II.ix.1). ‘Perception seems to me to be what distinguishes the animal kingdom from the inferior parts of Nature’ (11). ‘Perception is the first step towards knowledge, and is the inlet through which all its materials come into the mind’ (15).

Locke has followed the example of Descartes, Gassendi, and other Cartesians in giving the name ‘perception’ to the bare conception of things. And he has been followed in this by Berkeley, Hume, and many recent philosophers when they discuss ideas. They were probably led into this impropriety by the common theory of ideas, which teaches us that conception, sense-perception, and memory are only ·three· different ways of perceiving ideas in our own minds. If that theory is well founded, it will indeed be very hard to find any specific distinction—·any radical difference of kind·—between conception and perception. But there is reason to distrust any philosophical theory when it leads men to corrupt language and to run together under one name operations of the mind that common sense and ordinary language teach them to distinguish.

[Reid next concedes that it can happen that someone mistakes his mere conceptions with perceptions or memory— in some kinds of illness, in madness, or in cases where a memory is ‘so very weak’ that the person wonders whether ‘dreamed or imagined it’. He also conjectures that a very young child may say things that are untrue not because he is a liar but because he has ‘mistaken the rovings of his own fancy for things that he remembers’. Then:]

Granting all this, I assert that people whose intellectual faculties are sound and sober and mature can distinguish with certainty •what they perceive or remember from •what they merely conceive, when those operations have any degree of strength and clarity. [He goes on to say that ordinary good sense and intellectual competence enables one to avoid running these mental operations together, and that it is inexcusable that philosophers should commit such a blunder when they are theorizing about ideas. Then:]

Coming back now from this digression into which the misuse of the word ‘perception’ by philosophers has led me: it appears evident that the bare conception of an object, not including any opinion or judgment, can’t be either true or false. Truth and falsity, with those words taken in their proper senses, are altogether inapplicable to this operation of the mind.

(3) Of all the analogies between the operations of body and those of the mind, the strongest and most obvious to all mankind is the analogy between •painting or other creative arts and •the power of conceiving objects in the mind. That is why in every language the words used to refer to this power of the mind and its various special cases are analogical, being borrowed from the creative arts. We consider this power of the mind as a creative power that enables us to make for ourselves images [= ‘likenesses’] of the objects of thought.

It’s useless to try to avoid •this analogical language, for we have no other language on the subject; yet •it is dangerous and apt to mislead. All analogical and figurative words have a double meaning; and if we aren’t very careful we’ll slide unknowingly from the borrowed and figurative meaning of a word into its original literal meaning. We are apt to carry the parallel between the things compared—·in our present case, between paintings and conceptions·—further than it will hold, and thus very naturally to fall into error.

To avoid this as far as possible in our present context, we should attend to the dissimilarity between •conceiving a thing in the mind and •painting it for the eye, as well as to their similarity. The similarity impresses us and gives us pleasure; and we are less inclined to notice the dissimilarity. But the philosopher ought to attend to it, and to bear it in mind continuously in his reasonings on this subject, as a monitor to warn him against the errors into which the analogical language is apt to draw him.

When a man paints, he produces a work that remains when his hand is taken off, and continues to exist even if he doesn’t think of it again. Every stroke of his brush produces an effect, and this effect is different from his action in making it because it continues to exist when the action stops. The action of painting is one thing, a cause; the picture produced is another, the effect.

Now let us consider what is done when he only conceives this picture. He must have conceived it before he painted it; for everyone agrees that every work of art must first be conceived in the mind of the artist. What is this conception? It is an act of the mind, a kind of thought. This can’t be denied. But does it produce any effect besides the act itself? Surely common sense answers No to this question. For everyone knows that it is one thing to conceive something, another thing to actually make it. It is one thing to plan, another to carry out. A man may spend a long time thinking about what to do, and then do nothing. Conceiving, as well as planning and deciding, are what the schoolmen called ‘immanent’ acts of the mind, which produce nothing beyond themselves. But painting is a ‘transitive’ act which produces an effect distinct from the operation, namely the picture. [‘Immanent’ comes from Latin meaning ‘remaining within’; ‘transitive’ comes from Latin meaning ‘going across’, which implies ‘going outside’.] So don’t lose sight of the fact that what is commonly called ‘the •image of’ a thing in the mind is nothing more than the •act or operation of the mind in conceiving the thing.

This is the common sense of men who haven’t been tutored by philosophy, as their language shows. If someone ignorant of the language were to ask what ‘conceiving a thing’ means, we would find it natural to answer that it is having an image of it in the mind; and that may be the best explanation we have. This shows that ‘conception’ and ‘image’ of a thing in the mind are synonymous expressions. So the image in the mind is not the •object of conception, nor is it any •effect produced by conception as a cause. It is •conception itself. . . .

[Reid acknowledges that many philosophers maintain that in conception what one conceives is a ‘real image’ = thing-like image [from Latin res = ‘thing’], and that this is distinct from the act of conceiving it. He will discuss this view, he says, in his next chapter.]

(4) Keeping the content of (3) in mind, to guard us against being misled by the analogical language used on this subject, I point out a very strong analogy not only between

•conceiving in general and •painting in general

but also between

different •kinds of conceptions and different •kinds of painting.

The painter either (a) makes imaginative pictures, or (b) he paints from real objects of art or Nature that he has seen, or (c) he copies from the paintings of others. I think our conceptions admit of a very similar division.

(a) There are conceptions that may be called imaginative pictures. [Reid gives examples, e.g. Swift’s conception of Lilliput. These can’t be either true or false, he says, ‘because they aren’t accompanied by any belief and don’t imply any affirmation or negation’. Then he turns to two kinds of conceptions that ‘have an original or archetype to which they refer and with which they are believed to agree’, and thus a basis on which they could be called true or false:]

(b) We have conceptions of individual things that really exist, such as the city of London or the government of Venice; these are analogous to pictures taken from the life. . . .

Individual things that really exist were created by God (though some of them may have been shaped up by man), and only God knows their whole nature. We know them only in part, so our conceptions of them must always be incomplete and inadequate; yet they may be true and sound as far as they go.

(c) Analogous to paintings that are copies of earlier paintings, we have conceptions of what the ancients called universals—i.e. of things that do or could belong to many individuals. These are •kinds and •species of things, such as man or elephant, which are species of substances; wisdom and courage, which are species of qualities; equality or similarity, which are species of relations.

‘From what originals are these conceptions formed? And when are they said to be true or false?’ It seems to me that the original from which such a conception is copied—i.e. the thing that is conceived—is the conception or meaning that other competent speakers of the language attach to the same words. ·That is what makes conceptions of universals analogous to paintings of paintings·.

Things are divided up into kinds and sorts not by •Nature but by •men. We are connected to so many individual things that we couldn’t possibly give each of them its own individual name. If we are to get the knowledge of them that is needed for thought and talk about them, we have to sort them according to their different attributes. Those that have certain attributes in common are lumped together in one compartment and given a general name that belongs equally to every individual in that compartment. This common name must, therefore, signify the attributes that have been observed to be common to every individual in that compartment and to nothing else.

All that is needed for such a general word to fulfil its purpose is that all those who use it should attach the same meaning or notion—i.e. the same conception—to it. The common meaning is the standard by which such conceptions are formed, and they are said to be true or false according to whether they agree or disagree with that common meaning. Thus my conception of felony is true and sound when it agrees with the meaning of ‘felony’ in the laws relating to it and in authors who understand the law.

The thing that is conceived is the meaning of the word; and that meaning is the conception attached to the word by those who best understand the language.

An individual is signified in language either by •a proper name or by •a general word joined to further details that distinguish the given individual from all others. If we don’t know enough details about it, the individual—if it is an object of sense, and is nearby—can be pointed out to the senses. And if it is not within reach of the senses, we may be able to fix it by a description which, though very incomplete, may be true and sufficient to distinguish this individual from every other. So when we are speaking of individuals, we are very little in danger of mistaking the object or taking one individual to be another.

But, I repeat, our conception of an individual is always inadequate and lame. Individual things are the creatures of •God, and there are many facts about them that •we don’t know and can’t deduce by reasoning from what we do know. They have a real essence or natural constitution from which all their qualities flow; but our faculties don’t comprehend this essence. That is why individual things can’t be defined; for a definition ought to include the whole nature or essence of the thing defined. . . .

Universals are always expressed by general words; and all the words of a language except for proper names are •general words; they are the signs of •general conceptions. . . . These general conceptions are formed for the purpose of language and reasoning; and the object •from which they are taken and •with which they are intended to agree is the conception that other men attach to the same words. So these conceptions—·unlike our conceptions of individuals·— can be adequate, and can completely agree with the thing conceived. All this means is that men who speak the same language may completely agree in their meanings for many general words.

Thus, mathematicians have conceived what they call a ‘plane triangle’. They have defined it precisely, and when I conceive it to be a plane surface bounded by three straight lines I have a conception of it that is both true and adequate. Every property of plane triangles is either included in this conception or deducible from it by valid reasoning. This definition expresses the whole essence of the thing defined, as every good definition ought to do; but this essence is only what Locke very properly calls a •‘nominal essence’; it is a general conception formed by the mind and joined to a general •word as its sign. [‘Nominal’ come from Latin nomen = ‘name’.]

If all the general words of a language had a precise meaning, and were perfectly understood as mathematical terms are, all verbal disputes would be at an end and men would seem to differ in opinion only when they really did differ. But this is far from being the case. [Reid elaborates that point a little, and then concludes (4) thus:]

Our conceptions, therefore, appear to be of three kinds. They are either (b) the conceptions of individual things, the creatures of God; or they are (c) conceptions of the meanings of general words; or they are (a) the creatures of our own imagination. And these different kinds of conceptions have different properties, which I have tried to describe.

(5) Our conception of things can be anywhere on a scale from •very strong and lively down to •very faint and languid. These are qualities that properly belong to our conceptions, though we have only analogical names for them. Everyone is conscious of his conceptions’ differing in this way, and greatly enjoys his lively conceptions when the object isn’t of a painful sort.

Those who have lively conceptions commonly express them in a lively manner, i.e. in such a way that they arouse lively conceptions and emotions in others. People like that are the most agreeable companions in conversation, and the most acceptable in their writings.

[Reid continues through several paragraphs describing some of the causes of the liveliness of conceptions, e.g. their being associated with strong emotions. He ends (5) with:]

When ‘imagination’ is distinguished from ‘conception’, it seems to me to signify one sort of conception, namely conception of visible objects. Thus, in a geometrical proposition I imagine the diagram and I conceive the demonstration; I think it would be all right to say that I •conceive both; but it would be less correct to say that I •imagine the demonstration.

(6) Our conceptions of things may be •clear, distinct, and steady, or they may be •obscure, indistinct, and wavering. The liveliness of our conceptions gives pleasure; but their distinctness and steadiness are what enable us to judge rightly and to express our sentiments clearly.

Why do we find, among people speaking or writing on the same subject, so much •darkness in one and so much •clarity in another? I think that the chief cause is that one had a •distinct and steady conception of what he said or wrote, and the other •didn’t. Men usually find ways to express distinctly what they have conceived distinctly. . . . But a man can’t possibly express distinctly something that he hasn’t conceived distinctly. . . .

I think that indistinct conceptions of things usually cause not only •obscurity in writing and speaking but also •error in judging. [Reid goes on to say—using examples from geometry—that the main source of difference of opinion is difference of conception. Then:]

If this is really so, as it seems to be, it leads me to think that men are very much on a level with regard to mere •judgment, when we consider that faculty separately from the apprehension or conception of the things about which we judge; so that sound judgment seems to be the inseparable companion of clear and steady apprehension. We oughtn’t to consider judgment and conception as two talents, of which it could be the case that you have just one of them and your neighbour has just the other. Rather, they are talents that always go together.

Still, I would point out that some of our conceptions may be more usable in reasoning than others that are equally clear and distinct. I remarked earlier that some of our conceptions are of individual things, others of general and abstract things. It can happen that a man who has very clear conceptions of individual things is not so good at conceiving things that are general and abstract. I take this to be the reason why we find men who have good judgment in matters of common life, and perhaps good talents for poetical or rhetorical composition, yet find it very difficult to enter into abstract reasoning.

I don’t want to seem out on my own in putting men so much on a level in respect of mere judgment, so let me support this opinion by the authority of two very thoughtful men, Descartes and Cicero. Descartes writes:

Judgment is the best shared-out thing in the world. . . . So it seems reasonable to believe that the power of judging well and of telling the true from the false— which is what we properly call ‘judgment’ or ‘right reason’—is naturally equal in all men; so when our opinions differ it’s not because some of us are more reasonable than others but solely because we take our thoughts along different paths and don’t attend to the same things. (Discourse on the Method 1)

[Reid adds a short quotation to the same effect from Cicero’s third book of orations.]

From what I have said in (6), it follows that to the extent that it is in our power to form clear and distinct conceptions of the subject on which we speak or reason, to that extent it is in our power to write and speak clearly and to reason soundly. Nature has put a wide difference between one man and another in respect of ability to conceive clearly, but still it can’t be doubted that it is in a very considerable degree in our power to have clear and distinct apprehensions of things about which we think and reason.

(7) Many authors have noted that when we merely conceive any object, the ingredients of that conception must be either •things with which we were previously acquainted through some other original power of the mind or •parts or attributes of such things. Thus, a man can’t conceive colours if he has never seen anything, or sounds if he has never heard anything. He can’t conceive what is meant by moral obligation, or by right and wrong in conduct, if he doesn’t have a conscience.

Imagination can combine things that never were combined in reality. It can enlarge or diminish, multiply or divide, compound and build up the objects that Nature presents; but it can’t by the utmost effort of that creative power that we ascribe to it bring into its productions any simple ingredient that Nature hasn’t produced and brought to our knowledge by some other faculty.

Locke has expressed this beautifully and correctly:

Man’s power over this little world of his own understanding is much like his power over the great world of visible things, where he can only compound and divide the materials that he finds available to him, and can do nothing towards the making the least particle of new matter, or destroying one atom of what already exists. Everyone will find that he is unable to construct in his understanding any simple idea that he hasn’t received by the powers that God has given him. (Essay II.ii.2)

I think all philosophers agree about this. Hume, indeed, after acknowledging the truth of the principle in general, mentions what he thinks is a single exception to it: a man who has seen all the shades of a particular colour except one might form in his mind a conception of the shade that he never saw. I don’t think this is an exception; because a particular shade of a colour differs from other shades of the same colour only in degree and not in kind.

It should be noted that our most simple conceptions are not the ones that Nature immediately presents to us. When we come to years of understanding, we have the power of •analysing the objects of Nature, of •distinguishing their various attributes and relations, of •conceiving those attributes and relations one by one, and of •giving to each a name whose meaning extends only to that single attribute or relation. And thus our simplest conceptions are not those of any object in Nature, but of some single attribute or relation of such objects.

Thus, Nature presents to our senses bodies that are solid and extended in three dimensions. By analysing the notion of body that we get from our senses, we form the conceptions of

extension,

solidity,

space,

a point,

a line,

a surface;

which are all simpler conceptions than that of body. But they are the elements (as it were) •out of which our conception of body is made up, and •into which it can be analysed. I shall discuss this power of analysing objects in another place [Essay 5, chapter 3.] My only reason for mentioning it here is to prevent the content of (7) from being (mis)understood in such a way as to be inconsistent with it.

(8) Though our conceptions must be restricted to the ingredients mentioned in (7), there are no restrictions on how we can arrange those ingredients. In this we can pick and choose, forming an endless variety of combinations and compositions, which we call creatures of the imagination. We can conceive these clearly, even if they ·are of things that· never existed. And indeed everything that is •made must have been •conceived before it was made. Every work of human art, and every plan of conduct (whether in public or in private life), must have been conceived before being put into practice. And we cannot help thinking that God, before exercising his power by creating the universe, had a distinct conception of the whole and of every part, and saw it to be good and to be what he wanted.

It is the business of man, as a rational creature, to employ his unlimited power of conception for planning his conduct and enlarging his knowledge. It seems that only beings endowed with reason can act on a preconceived plan. Brute animals seem either to lack this power or to have it in a very low degree. They are moved by instinct, habit, appetite, or natural affection, according as these sources of energy are stirred up by the animal’s situation at the given moment. But I see no reason to think that animals can envisage a connected plan of life, or form general rules of conduct. Indeed, we see that many humans to whom God has given this power make little use of it. They act without a plan, going wherever they are led by the emotion or appetite that is strongest at the time.

(9) The last property of •the power of conception that I shall mention is the one that essentially distinguishes •it from every other power of the mind. namely: •it is not employed solely about things that exist. I can conceive a winged horse as easily and as distinctly as I can conceive a man whom I have seen. And this distinct conception doesn’t give me the faintest inclination to believe that a winged horse ever existed.

The other operations of our minds are different in this respect. They are employed on things that really exist, and carry with them a belief in their objects. When I feel pain, I am forced to believe that the pain I feel really exists. When I perceive any external object, my belief in its real existence is irresistible. When I distinctly remember any event, even one that no longer exists, I cannot doubt that it did exist. The consciousness we have of the operations of our own minds implies a belief in the real existence of ·the objects of· those operations.

Thus we see that the powers of sensation, perception, memory, and consciousness are all employed solely about objects that do exist or have existed. But conception is often employed about objects that neither do nor did nor will exist. This is the very nature ·or essence· of this faculty that its object, though clearly conceived, may have no existence. We call such an object a ‘creature of imagination’, but this ‘creature’ was never created!

So as not to get in a muddle about all this, we must distinguish •the act or operation of the mind that we call ‘conceiving an object’ from •the object that we conceive. When we conceive something, there is a real act or operation of the mind; we are conscious of this, and can have no doubt of its—·i.e. the act’s·—existence. But every such act must have an object—you can’t conceive unless you conceive something—and it may be that this object never existed.

If you haven’t been acquainted with the doctrine of philosophers on this subject, I’m afraid you will think I am making a fool of myself by insisting on something as obvious as the fact that men can conceive things that never existed. You’ll hardly believe that any man in his wits ever doubted this. Indeed, I know no truth more evident to the common sense and to the experience of mankind. But if it is opposed by the authority of philosophy, ancient and modern, as I think it is, I don’t want to treat that authority so contemptuously as not to attend patiently to what can be said in support of it.

Chapter 2: Theories about conception

The theory of ideas has been applied to the •conception of objects as well as to •perception and •memory. It may be as tiresome for you as it is for me to return to the theory of ideas when I have already said so much about it; but ·there is a sober reason for coming back to it·. Its application to the •conception of objects couldn’t suitably have been introduced until now, and studying this one application will provide a more comprehensive view of the theory and of the prejudices that have led philosophers so unanimously to accept it.

The theory of ideas, in all the various forms it has taken during more than two thousand years, seems to me to have arisen from ·two· prejudices. These get no support from the natural dictates of our faculties, or from attentive reflection on their operations; but they are prejudices that those who theorize about this subject are very apt to be led into by analogy.

(1) In all the operations of the understanding, there must be some immediate communication between the mind and its object, so that the one can act on the other.

(2) In all the operations of understanding, there must be an object of thought that really exists while we are thinking of it—or (as some philosophers have put it) what doesn’t exist can’t be intelligible.

If philosophers had seen that these are merely prejudices, and based purely on analogical reasoning, we would never have heard of ‘ideas’ in the philosophical sense of that word.

(1) The first of these principles has led philosophers to think that, because the external objects of sense are too remote to act on the mind immediately, there must be some image or shadow of them that is present to the mind and is the immediate object of perception. That there is such an immediate object of perception, distinct from the external object, has been unanimously held by philosophers, though they have disagreed considerably about the name, the nature, and the origin of those immediate objects.

I have discussed what has been said in the support of this principle in Essay 2, chapter 4, to which I refer you now, so as not to say it all again. I have just one thing to add to what I said there. There seems to be no shadow of reason why the mind must have an object immediately present to it in its •intellectual operations, any more than in its •affections and •emotions. Philosophers haven’t said that ideas are the immediate objects of love or resentment, of esteem or disapproval. It is accepted, I think, that the immediate objects of those affections [here = ‘non-cognitive states’] are persons and not ideas. Yet persons are as far from being immediately present to the mind as other external objects are; and sometimes the object of one’s love, disapproval etc. is a person who doesn’t now exist and therefore can’t act on the mind or be acted on by it.

(2) The second principle flatly contradicts what I said in (9) in the preceding chapter, namely that we can have a distinct conception of things that never existed. This is undoubtedly the common belief of people who haven’t been instructed in philosophy, and they will think it as ridiculous to defend it by reasoning as to oppose it.

The philosopher says:

Though there may be a remote object that doesn’t exist, there must be an immediate object that really exists; for something that doesn’t exist can’t be an object of thought. The idea must be perceived by the mind; and if it doesn’t exist in the mind, there can be no perception of it, no operation of the mind concerning it.

There is all the more reason to examine this because principle (1) depends on it. It could be that (2) is true and (1) false, but it can’t be the case that (1) is true and (2) false. If we can conceive objects that have no existence, it follows that there can be objects of thought that don’t act on the mind and aren’t acted on by it; because something that has no existence can’t either act or be acted on.

These two principles have led philosophers to think that in every act of memory and of conception, as well as of perception, there are two objects:

•the immediate object—the idea, the species [Aristotelian technical term], the form; and

•the mediated or external object.

The vulgar know of only one object, which in perception is some external thing that does exist, in memory something that did exist; and in conception it may be something that never existed. But the immediate object of the philosophers, the ‘idea’, is said to exist and to be perceived in all these operations.

These principles have not only led philosophers to split objects into two where others can find only one, but likewise have led them to reduce the •three operations I have just mentioned to •one, taking memory and conception (as well as perception, ·properly so-called·) to be the perception of ideas. But to •the vulgar it seems utterly obvious that what is only remembered or only conceived is not perceived; and to speak of the ‘perceptions of memory’ appears to them as absurd as to speak of the ‘hearing of sight’.

In short, these two principles carry us into the whole philosophical theory of ideas and furnish every argument that ever was used for their existence. If the principles are true, the ‘ideas’ system must be admitted, with all its consequences. If they are only prejudices based on analogical reasoning, the whole system must fall to the ground with them.

So it is important to trace those principles back as far as we can to their origin, to see whether they might have some firm foundation in reason rather than being rash conclusions drawn from a supposed analogy between matter and mind.

The uneducated, who are guided by the dictates of Nature and express what they are conscious of concerning the operations of their own mind, believe that the object they clearly perceive certainly exists, that the object that they clearly remember certainly did exist but now may not; but as to things that are barely conceived, they know they can conceive a thousand things that never existed ·and never will·, and that the bare conception of a thing doesn’t create even a presumption of its existence. They don’t trouble themselves to know how these operations are performed, or to explain them in terms of general principles.

But philosophers, who want to discover the causes of things and to explain these mental operations, having observed that in physical operations there must be not only something that acts but something that is acted on, have been led by analogy to conclude that it must also be like that with the operations of the mind.

The relation between •the mind and •its conceptions bears a very strong and obvious analogy to the relation between •a man and •his work. Every scheme a man forms, every discovery he makes by his reasoning powers, is very properly called the ‘work’ of his mind. These works of the mind are sometimes great and important works that attract men’s attention and admiration.

It is the philosopher’s business to consider how such works of the mind are produced, and what materials they are composed of. He calls the materials ‘ideas’. So there have to be ideas that the mind can arrange and form into a regular structure. Everything that is produced must be produced out of something; nothing can be produced from nothing..

Some such reasoning as this seems to me to have first given rise to the philosophical notions of ideas. Those notions were formed into a system by the Pythagoreans two thousand years ago; and this system was adopted by Plato, who polished and decorated it with all the powers of his fine and lofty imagination. I shall go along with customary usage and call it the ‘Platonic’ system of ideas, though really it was the invention of the Pythagorean school.

The hardest question that exercised the minds of men in the infancy of Greek philosophy was: What was the origin of the world? From what sources and causes did it come? This was answered differently by the different schools ·of philosophy·. Most of the answers strike us as quite ridiculous. But the Pythagoreans judged very rationally, from the order and beauty of the universe, that it must be the work of an eternal, thinking, and good being. So they concluded that the Deity is one first source or cause of the universe.

But they thought there must be more. The universe must be made of something. Every workman must have materials to work on. That the world should be made out of nothing seemed to them absurd, because every thing that is made must be made of something. Lucretius wrote: ‘Divine power never produces something out of nothing.’ Persius wrote: ‘Nothing can come out of nothing, and nothing can return into nothing.’ [Reid gives these in their original Latin.] This maxim was never called into question. . . . Because men must have materials to work on, they all inferred it must be so with the Deity also. This was reasoning from analogy.

From this it followed that an eternal uncreated matter was another first source of the universe. But this matter, they believed, had no form, no qualities. It was the same as the ‘prime matter’ of Aristotle, who borrowed this part of his philosophy from his predecessors.

To us it seems more rational to think that •the Deity created matter along with its qualities than that •the matter of the universe is eternal and self-existent [= ‘existing in its own right (so to speak), not needing anything else to bring it into existence or keep it in existence’]. But the ancient philosophers were so strongly prejudiced against what we call ‘creation’ that they preferred to fall back on this eternal and unintelligible ‘matter’, so that the Deity would have materials to work on.

The same analogy that led them to think that •there must be an eternal matter of which the world was made led them also to conclude that •there must be an eternal pattern or model according to which it was made. Works of ·human· design and art must be clearly conceived before they are made. The Deity, as a thinking being about to carry out a work of perfect beauty and regularity, must have had a clear conception of his work before it was made. This appears very reasonable.

But because this conception was the work of the divine intellect, something must have existed as its object. This could only be ideas, which are the proper and immediate object of intellect.

From this investigation of the sources or causes of the universe, those philosophers concluded that there were three of them: •eternal matter as the material cause, •eternal ideas as the model or exemplary cause, and an •eternal thinking mind as the efficient cause. [It’s the last of these three that means ‘cause’ in your and my sense.]

As for the nature of those eternal ideas, the Pythagorean philosophers ascribed to them the most magnificent attributes. They were

•unchanging and uncreated,

•the object of God’s intellect before the world was made, and

•the only object of intellect and of science to all thinking beings.

As far as intellect is superior to sense, so far are ideas superior to all the objects of sense. The objects of sense being in a constant flux, can’t properly be said to exist. Ideas are the things that have a real and permanent existence. They are as various as the species of things, there being one idea for every species but none for individuals. The idea is the essence of the species, and existed before any of the species were made. This idea or essence exists in its entirety in every individual member of the species, without being either divided or multiplied.

In our present state, we have only an imperfect conception of the eternal ideas; but it is the greatest happiness and perfection of men to be able to contemplate them. While we are in this prison of the body, sense acts as a dead weight pulling us down from the contemplation of the intellectual objects; and it is only by the right kind of purification of the soul and abstraction from the senses that the eye of the intellect is opened and we become able to rise on the wings of intellect to the heavenly world of ideas.

Such was the most ancient theory of ideas of which we have any account. And however different from the modern theory it may be, it seems to be based on the two prejudices I have mentioned—that in every operation there must be something to work on, and that even in conception there must be an object that really exists.

For if those ancient philosophers had thought that the Deity could make the world without •materials, and could conceive the plan of the world without a •model, they couldn’t have thought they had any reason to make •matter and •ideas eternal and necessarily existent sources along with the Deity himself.

I don’t know whether the Pythagoreans believed that the status of eternal and existing without a cause was possessed not only by •the ideas individually but also by •the beautiful and perfect order—·the structure of ideas·—that they ascribed to this intelligible world of ideas. But this latter seems to be a necessary consequence of the Pythagorean system. For if the Deity couldn’t conceive the plan of the world that he made without a really existing model, that model couldn’t be his work or devised by his wisdom; for if he made it, he must have conceived it before it was made; so it must have existed in all its beauty and order independently of the Deity; and I think the Pythagoreans were acknowledging this when they made the •model and the •matter of this world first sources—·utterly basic sources·—along with •the Deity.

If the Platonic system is understood in this way (and I don’t see how else it can hang together), it leads to two consequences that are unfavourable to it.

First, all that the maker of this world needs to have is the skill to work under the guidance of a model. The model had all the perfection and beauty that appears in the copy, and God had only to copy a pattern that existed independently of him. ·And not to copy very accurately·: if we are to believe those philosophers, the copy falls very far short of the original ·model or plan·, but they seem to have blamed this on the stubbornness of the matter of which the world was made.

Secondly, if •the world of ideas could have so much beauty and perfection without being the work of a perfectly wise and good thinking being, how can we infer from the beauty and order of •this world—which is merely an imperfect copy of the original model—that it must have been made by a perfectly wise and good being? The force of the inference from •the universe’s beauty and order to •its being the work of a wise being—a force that seems irresistible to every candid mind, and seemed so to those ancient philosophers—is entirely destroyed by the supposition that there exists an even more beautiful and orderly world of ideas that was never made. And if on the other hand the inference is sound, it will apply also to the world of ideas, which must have been made by a wise and good thinking being and must have been conceived before it was made.

I would point out also that everything that is mysterious and unintelligible in Platonic ‘ideas’ arises from attributing existence to them. Take away this one attribute, and all the rest, however grandly expressed, are easy to understand and accept. ·I shall now show this·. What is a Platonic idea?

(1) It is the essence of a species.

(2) It is the exemplar, the model according to which all individual members of that species are made.

(3) It is entire in every individual of the species, without being multiplied or divided.

(4) It was an object of God’s intellect from eternity, and is an object of contemplation and of science to every thinking being.

(5) It is eternal, unchanging, and uncreated.

And, to crown all,

(6) it has a more real and permanent existence than anything that ever God made.

Take this description as a whole and it would require an Oedipus to unriddle it. But take away the last item—·the ‘crowning’ one·—and nothing is easier. It is easy to find five hundred things of which every other article in the description is true.

Take for an instance the nature of a circle as it is defined by Euclid, an object that any thinking being could conceive clearly even if no circle had ever existed.

(1) ·This is the essence of the species circle·.

(2) It is the exemplar, the model according to which all the individual circles that ever existed were made,

for they are all made according to the nature of a circle.

(3) It is entire in every individual circle, without being multiplied or divided,

for every circle is an entire circle; and all circles, insofar as they are circles, have one and the same nature.

(4) It was an object of God’s intellect from all eternity, and can be an object of contemplation and of science to every thinking being.

It is the essence of a species, and like all other essences

(5) it is eternal, unchanging, and uncreated.

This means merely that a circle always was a circle and can never be anything but a circle. It is the necessity of the thing, and not any act of creating power, that makes a circle be a circle.

The nature of every species—whether of substance, of quality, or of relation—and in general everything that the ancient philosophers called a ‘universal’, fits the description of a Platonic idea once you have removed from that description the attribute of existence.

If we believe that God could not conceive any species of things without having a really existing model, we’ll have to go back to the Platonic system, however mysterious it may be. But if it’s true that God could have a distinct conception of things that have never existed, and that other ·and lesser· thinking beings can conceive objects that don’t exist, the Platonic system has no better foundation than this prejudice that the mind’s operations of mind must be like the body’s.

Aristotle rejected the ideas of his master Plato as visionary; but he still had the prejudices that caused them, so he devised substitutes for Plato’s ‘ideas’, giving them a different name and telling a different story about how they arise.

He called the objects of the intellect ‘intelligible species’, those of memory and imagination ‘phantasms’, and those of the senses ‘sensible species’. This was indeed a very small change of name, because the Greek word of Aristotle’s that we translate as ‘species’ or ‘form’ is very near to the Greek word ιδα, both in sound and meaning, so that from their etymology it wouldn’t be easy to give them different meanings. Both are derived from a Greek word meaning ‘to see’, and both can signify a vision or appearance to the eye. Cicero, who understood Greek well, often translates the Greek ιδα by the Latin word visio [= ‘vision’]. But since both words were being used as technical terms—one in the Platonic system, the other in the Aristotelian one—the Latin writers generally borrowed the Greek ιδα to express the Platonic notion, and translated Aristotle’s word by the words ‘species’ or ‘forma’; and in this they have been followed in the modern languages. Those forms or species were called ‘intelligible’ to distinguish them from ‘sensible’ species, which Aristotle held to be the immediate objects of sense.

He thought that the ‘sensible species’ come from the external object, and he defined a sense to be something that can receive the form of sensible things without the matter, as wax receives the form of a seal without any of its matter. Similarly, he thought that •the intellect receives the forms of intelligible things, and he calls •it the ‘place of forms’.

I take it to have been Aristotle’s opinion that the •intelligible forms in the human intellect are derived from the •sensible ones by abstraction and other operations of the mind itself. As for the intelligible forms in God’s intellect: they must have had some other origin, but I don’t remember that Aristotle says anything about them. He certainly maintained that there is no abstract thought without intelligible species, no memory or imagination without phantasms, no perception without sensible species. Treating of memory, he presents (and tries to solve) a difficulty about how a phantasm that is a present object in the mind could represent a thing that is past.

Thus I think it appears that the Aristotelian system of species and phantasms, as well as the Platonic system of ideas, is based on this principle that in every kind of thought there must be some object that really exists; in every operation of the mind there must be something to work on. In our present context it doesn’t matter whether this immediate object is called an ‘idea’ with Plato or a ‘phantasm’ or ‘species’ with Aristotle, or whether it is eternal and uncreated or produced by the impressions of external objects. Either way, and in both systems, it was thought impossible for God to make the world without matter to work on. And in both it was thought impossible for a thinking being to conceive anything that didn’t exist except by means of a model that really existed.

The later Platonists thought the eternal ideas of things to be in God’s intellect, thereby avoiding the absurdity of making them something distinct from and independent of God; but still they held that these ideas really exist in the Divine mind, as the objects of conception and as the patterns and archetypes [= ‘things to be copied’] of things that are made.

Modern philosophers, still convinced that every thought must have an immediate object that really exists, haven’t thought it necessary to distinguish by different names the immediate objects of intellect, of imagination, and of the senses, but have given them all the common name ‘idea’.

On certain points different modern philosophers seem to have different opinions, and sometimes the same author seems to waver between one view and another, or to hesitate to take either side. I mean such issues as these:

•Are these ideas in the sensorium or in the mind, or partly in the one and partly in the other?

•Do they exist when they aren’t perceived or only when they are perceived?

•Are they the workmanship of God or of the mind itself or of external natural causes?

But as to the existence of ideas there seems to be great unanimity.

This opinion is so firmly fixed in the minds of philosophers that I’m sure that most will think it a very strange paradox—or rather a contradiction—to say that men think without ideas. I agree that it appears to be a contradiction; but this appearance arises from the ambiguity of ‘idea’. If the ‘idea’ of a thing means only the thought of it, or the operation of the mind in thinking about it (which is the most common meaning of the word), to •think without ideas is to •think without thought—and that certainly is a contradiction.

But according to the definition of ‘idea’ given by philosophers, an idea is not •thought but •an object of thought that really exists and is perceived. Now, is it a contradiction to say that a man can think of an object that doesn’t exist? I agree that a man can’t •perceive an object that doesn’t exist, or •remember an object that didn’t exist; but I can’t see any contradiction in his •conceiving an object that doesn’t and never did exist. [He gives the example of conceiving a centaur. Then:]

The philosopher says ‘I can’t conceive a centaur without having an idea of it in my mind.’ I am at a loss to understand what he means. He surely doesn’t mean ‘I can’t conceive a centaur without conceiving it’—that would make me no wiser! What, then, is this ‘idea’? Is it an animal, half horse and half man? No. Then I am certain it isn’t the thing I conceive. The philosopher may say that the idea is an image of the animal, and is the immediate object of my conception; and that the animal is the mediate or remote object.

I have three answers to this. (1) I am certain there are not two objects of this conception of mine, but only one, and it is as immediate an object of my conception as any can be.

(2) This one object that I conceive is not the image of an animal, it is an animal. I know what it is to conceive an image of an animal, and what it is to conceive an animal; and I can tell these apart with no danger of getting it wrong. The thing I conceive is a body of a certain shape and colour, having life and spontaneous motion. The philosopher says that the idea is an image [= ‘likeness’] of the animal, but that it has neither body nor colour nor life nor spontaneous motion. I can’t make sense of this.

(3) How does this idea come to be an object of my thought, when I can’t even conceive what ‘idea’ means; and even if I did conceive it, this wouldn’t be evidence of its existence any more than my conception of a centaur is evidence of its existence. Philosophers sometimes say that we ‘perceive’ ideas, sometimes that we ‘are conscious of’ them. I can have no doubt of the existence of anything that I either perceive or am conscious of, but I can’t find that I either perceive ideas or am conscious of them.

•Perception and •consciousness are very different operations, and it is strange that philosophers have never settled which of them we use to discern ideas. It’s as though someone were to insist that he had perceived a certain object but didn’t know whether he had seen it or felt it or heard it.

But if a man conceives a centaur, isn’t it all right for him to say that he has a clear image of it in his mind? I think it is. And if he means by this what the vulgar would mean by it—the vulgar, who have never heard of the philosophical theory of ideas—I find no fault with it. By a ‘clear image’ in the mind the vulgar mean a clear conception; and it is natural to call it an ‘image’ because of the analogy between an image of a thing and the conception of it. On account of this analogy, which is obvious to all mankind, this operation is called ‘imagination’ and an ‘image in the mind’ is only a round-about way of saying ‘ imagination’. But to infer from this that there is really an image in the mind, distinct from the operation of conceiving the object, is to be misled by an analogical expression; as though we were to infer from talk about deliberating [from the Latin librare = ‘weigh’] and ‘balancing’ things in the mind that the mind really does contain a balance for weighing motives and arguments.

The analogical words and phrases that all languages use to express conception no doubt encourage their being taken in a literal sense. But if we attend carefully to what we are conscious of in conception—attend to that and nothing else—we’ll find no more reason to think that images really exist in our minds than that balances and other mechanical contraptions do.

Everything we know about what is in the mind we know by consciousness, and all we are conscious of are various ways of thinking—such as understanding, willing, affection, passion, doing, undergoing. If philosophers choose to give the name ‘idea’ to any way of thinking of which we are conscious, I have no objection to the name except that it introduces into our language a foreign word that we have no need for, a word that is very ambiguous and apt to mislead. But if they use ‘idea’ to refer to images in the mind that are not instances of thinking but rather objects of thought, ·then I do object to the name ‘idea’ because· I can see no reason to think that there are such things in Nature. ·Don’t say ‘Perhaps there are such objects in your mind, but they lurk there in a form that makes it hard for you to detect them·’. If there are such objects in our minds, their existence and their nature should be more evident than anything else, because ·according to the friends of the theory of ideas· they are our only route to anything that we know! I would add that if they exist in the mind, we can’t know anything else. For there is no sound reasoning that will take us from the existence of images to the existence of anything else, except perhaps the existence of a thinking author of them. In this Berkeley reasoned correctly.

In every •work of design, the work must be conceived before it is carried out, i.e. before it exists. [That is now restated in terms of the specific example of a house, to make it a little easier to grasp. Reid gave no such example.] When someone is designing a house, the house must be conceived before the building work is done—i.e. before the house exists. If conceiving the house involves having in one’s mind a model consisting of ideas, that model is a •work of design just as much as the house of which it is the model. And therefore as a work of design it must have been conceived before it existed—·and so we are launched on an infinite regress·. Earlier [here] I applied this argument to the Platonic system of eternal and unchanging ideas, and it can be applied with equal force to all the systems of ideas.

·Now for some questions and my answers·.

What is the idea of a circle? It is the conception of a circle. What is the immediate object of this conception? The immediate and only object of it is a circle.

Where is this circle? It is nowhere. If it were an individual and had a real existence, it would have to have a place; but being a universal it has no existence and therefore no place. Isn’t it in the mind of him who conceives it? The conception of the circle is in the mind because it is an act of the mind; and in common language ‘x is in the mind’ is a figurative way of saying that x is conceived or remembered.

Is this conception an image or likeness of a circle? Answer: I have already dealt with its being in a figurative sense called ‘the image of a circle’ in the mind. If the question is meant in the literal sense ·in which ‘image’ means ‘likeness’·, I have to begin my reply by pointing out that ‘conception’ has two meanings. Strictly (a) it stands for the operation of the mind that I have been trying to explain; but sometimes (b) it is used to signify the object of conceiving, i.e. the thing that is conceived. ·Thus, one question becomes two·:

Is (b) the conception—meaning the object of the conceiving—an image or likeness of a circle? The object of this conceiving is not an image or likeness of a circle, because it is a circle, and nothing can be an image of itself.

Is (a) the operation of conceiving a circle an image or likeness of a circle? No: no two things can be more perfectly unalike than a kind of thinking and a kind of shape.

Isn’t it strange that conceiving should be utterly unlike the object that is conceived? No more strange than that desire should have no resemblance to the object desired, or resentment to the object of resentment.

I can conceive an individual object that really exists, such as St Paul’s church in London. I have an idea of it, i.e. I conceive it. The immediate object of this conception is four hundred miles away [Reid lived in Edinburgh], and I have no reason to think that it acts on me or that I act on it; but I can think of it, nonetheless. I can think of the first year or the last year of the Julian period.

‘Despite all that you have said, images in the mind serve to explain our ability to conceive •things that are far away in time and place and even •things that don’t exist and that would otherwise be altogether inconceivable.’ I answer that ‘explanations’ of things based on conjectures have been the curse of true philosophy all through the centuries. Our experience of them—·specifically, our experience of their failure rate·—should convince us that it is a hundred times more probable that such an ‘explanation’ is false than that it is true.

This explanation of the faculty of conception in terms of images in the mind or in the brain will deserve the respect of those who have sound judgment in philosophy when four things have been proved by solid arguments: •That the mind or the brain contains images of the things we conceive. •That the mind has a faculty or capacity for perceiving such images. •That the perception of such images produces the conception of things that are most distant and even of things that don’t exist. •That the perception of individual images, in the mind or in the brain, gives us the conception of universals that are the attributes of many individuals. Until these are proved, the theory of images existing in the mind or in the brain ought to be put in the same box as Aristotle’s ‘sensible species’ and ‘prime matter’ and Descartes’s ‘vortices’.

Chapter 3: ·Four· mistakes about conception

(1) Writers on logic, following Aristotle’s example, divide the operations of the understanding into three—simple apprehension (which is another word for conception), judgment, and reasoning. They teach us that

•reasoning is expressed by a syllogism,

•judgment is expressed by a proposition [here = ‘sentence’], and

•simple apprehension is expressed by a term—i.e. by one or more words that don’t make a full proposition but only the subject or predicate of one.

If by this they mean, as I think they do, that a proposition or even a syllogism can’t be simply apprehended, I think they are mistaken.

Conception is included in all judgment and all reasoning. We can’t judge of a proposition or reason about it unless we conceive or apprehend it. We can distinctly conceive a proposition without judging of it at all. We may have no evidence for its truth or for its falsity, or we may have no interest in whether it is true or false. In these cases we commonly form no judgment about it, though we perfectly understand its meaning.

A man can discourse or plead or write for purposes other than to find the truth. His learning and wit and invention can be employed while his judgment is used not at all or very little. When what he is after is not truth but something else, judgment would be a nuisance except for •discovering the means to attaining his end; so he sets it aside or uses it solely for •that purpose.

An orator’s business, they say, is to find out what is likely to persuade. A man can do this very ingeniously without ever taking the trouble to examine whether it ought to persuade. So it shouldn’t be thought that a man makes a judgment about the truth of every proposition he utters or hears uttered. In our commerce with the world, judgment is not the talent that commands the greatest price; so those who are not sincere lovers of truth put this talent on a high shelf where it can sit and grow mouldy, while they carry to market other talents for which there is greater demand.

(2) Logicians usually divide simple apprehension into •sensation, •imagination, and •pure intellection—a classification that seems to me very improper in three respects.

First: under the word ‘sensation’ they include not only •sensation properly so called but also •the perception of external objects by the senses. These are very different operations of the mind; and although Nature commonly links them together, they ought to be carefully distinguished by philosophers.

Second: neither •sensation nor the •perception of external objects is ·a kind of· simple apprehension. Both include judgment and belief, which are excluded from simple apprehension.

Third: they distinguish •imagination from •pure intellection thus: in imagination the image is in the brain, in pure intellection it is in the intellect. This is to base a distinction on an ·ungrounded· hypothesis. We have no evidence that there are images either in the brain or in the intellect.

I take ‘imagination’ in its most proper sense to stand for a lively conception of visible objects. This is a talent of importance to poets and orators, and deserves a name of its own because of its connection with those arts. According to this strict meaning of the word, •imagination is distinguished from •conception as a •part from the •whole. We conceive the objects of senses other than sight, but it is less correct to say that we imagine them. We conceive judgment, reasoning, propositions, and arguments; but it is rather improper to say that we imagine these things.

This distinction between •imagination and •conception can be illustrated by an example that Descartes uses to illustrate the distinction between •imagination and •pure intellection. We can imagine a triangle or a square so clearly as to distinguish them from every other shape. But we can’t so clearly imagine a figure of a thousand equal sides and angles. No-one, however good his eye, could just by looking at it distinguish this from every figure with more or fewer sides. And the conception of its appearance to the eye that we properly call ‘imagination’ can’t be more distinct than the appearance itself; yet we can conceive a figure of a thousand sides, and can even demonstrate the properties that distinguish it from all figures of more or fewer sides. We form the notion of a great number such as a thousand not by the eye but by a higher faculty. And a distinct notion of this number of sides, since it can’t be acquired by the eye, is not imagined; but it is distinctly conceived and easily distinguished from every other number.

(3) Simple apprehension is commonly represented as the first ·or most basic· operation of the understanding; and judgment is taken to be a composition or combination of simple apprehensions.

This mistake has probably arisen from taking •sensation and the •sense-perception of objects to be nothing but simple apprehension. They very probably are the first ·or most basic· operations of the mind, but they aren’t simple apprehensions.

It is generally allowed that we can’t conceive sounds if we have never heard anything, or colours if we have never seen anything; and the same thing holds for the objects of the other senses. Similarly, we must have judged or reasoned before we can have the conception or simple apprehension of judgment and of reasoning.

So simple apprehension is not the •first operation of the understanding, though it is the •simplest; and instead of saying that the more complex operations of the mind are formed by compounding simple apprehensions, we ought rather to say that simple apprehensions are acquired by analysing more complex operations.

A similar mistake that runs all through Locke’s Essay may be mentioned here. It is that our simplest ideas or conceptions are acquired immediately through the senses or through consciousness, and complex ideas are then formed by compounding the simple ones. I think this is far from the truth.

Nature presents no object to the senses or to consciousness that isn’t complex. Thus, by our senses we perceive bodies of various kinds; but every body is a complex object with length, breadth, and thickness, with shape and colour and various other sensible qualities that are blended together in a single thing. And I think that brute animals who have the same senses that we have can’t separate the different qualities belonging to a single thing, and have only a complex and confused notion of the whole. Our own notions of the objects of sense would be like that if we didn’t have higher powers of understanding that enable us to analyse the complex object, abstract each particular attribute from the rest and form a distinct conception of it.

So we get the simplest and most distinct notions, even of the objects of sense, not immediately through the senses but rather through our ability to analyse and abstract. This will be more fully explained in another place [Essay 5].

(4) One further mistake about conception deserves to be noticed. It is that our conception of things is a test of their possibility, so that if we can distinctly conceive something we may infer that it is possible—i.e. we can have no conception of what is impossible.

This opinion has been held by philosophers for more than a hundred years, without any contradiction or dissent that I know of. If it is an error, it may be useful to look into its origin and into why it has been so generally accepted as a maxim whose truth couldn’t be questioned.

One of the pointless questions debated among scholastic philosophers in the dark ages was ‘What is the criterion of truth?’, as if men could have any way to distinguish truth from error other than through the proper use of their God-given power of judging!

Descartes tried to put an end to this controversy by making it a fundamental principle in his system that

•Whatever we clearly and distinctly perceive is true.

To understand this principle, you have to know that Descartes gave the name ‘perception’ to every power of the human understanding; and in explaining •this very maxim he tells us that sense, imagination, and pure intellection are only different kinds of perceiving, which is how the maxim was understood by all his followers.

[Reid then devotes a paragraph to Cudworth’s somewhat obscure statement of the ‘maxim’, including this: ‘If something is false, not even God’s power can make it clearly and distinctly understood’.]

This Cartesian maxim seems to me to have led the way to the one I am now considering, which seems to have been adopted as a corrected version of the former. When Descartes’s authority declined, men began to see that we can clearly and distinctly conceive something that isn’t true, but they thought that our conception, though not always a test of •truth, might be a test of •possibility.

It seems indeed to be an inevitable consequence of the received doctrine of ideas, because it is obvious that there can’t be a distinct image—in the mind or anywhere else—of something that is impossible. The ambiguity of the word ‘conceive’ which I noted in Essay 1, chapter 1, and the common way of saying ‘I can’t conceive x’ when we want to get across that we think x is impossible, might also have contributed to the acceptance of this doctrine.

Anyway, whatever the origin was of this opinion, it seems now to hold sway, accepted as a maxim, everywhere. [Reid then presents short quotations in which this ‘maxim’ is affirmed, by Clarke, Bolingbroke, Abernethy, Price, Wolff, and Hume. The only one he will refer back to (quite soon), is Wolff’s. It is in Latin meaning: ‘Something of which we can’t form any notion is impossible; something to which some notion corresponds is possible.’]

It would easy to round up many other respectable authorities for this maxim, and I have never found one who questioned it.

If the maxim is true in the strong form given it by Wolff in the passage quoted above, we’ll have a short road to the settling of every question about the possibility or impossibility of things. All we’ll need is to look into our own breast, which. . . .will give an infallible answer. If we can conceive the thing, it is possible; if we can’t, it is impossible. And surely everyone can know whether he can conceive a given proposition or not.

Other philosophers have settled for half of Wolff’s maxim: they say that whatever we can conceive is possible; but they don’t say that whatever we can’t conceive is impossible. I can’t help thinking that even this is a mistake—one that philosophers carelessly let themselves be led into by the causes I have mentioned. Here are my ·four· reasons for this judgment.

[We are going to meet the word ‘proposition’ quite often. Reid’s basic meaning for it is ‘sentence’: he speaks of what is ‘expressed by a proposition’ and of ‘the meaning of a proposition’. But sometimes a ‘proposition’ seems to be not •a sentence (a bit of language) but rather •what is meant by a sentence. Especially when Reid speaks of a proposition as possible, He doesn’t mean (for example) that the sentence ‘the speed of light is infinite’ is possible; obviously it is possible; it is actual; there it sits on the page! What he means is rather (to take the same example) that it is possible that the speed of light is infinite, where possibility is asserted not of the sentence but of what the sentence expresses. In this version, from here to the end of the chapter, ‘proposition’ will be left undisturbed.]

1. Whatever is said to be possible or impossible is expressed by a proposition. Now, what is it to conceive a proposition? I think it is merely to understand distinctly its meaning. I don’t know of anything else that can be meant by ‘simple apprehension’ or ‘conception’ when applied to a proposition. So the axiom amounts to this:

•Every proposition whose meaning you distinctly understand is possible.

Well, I’m convinced that I understand the meaning of this proposition:

(a) Any two sides of a triangle are together equal to the third

just as distinctly as I understand this:

(b) Any two sides of a triangle are together greater than the third;

yet (a) is impossible. You may want to object: ‘Although you understand the meaning of the impossible proposition (a), you can’t suppose or conceive it to be true.’ So now we have to examine the meaning of the phrases ‘supposing (or conceiving) a proposition to be true’. ·Taking them in their most natural sense·, they don’t help the ‘axiom’: I can certainly suppose (a) to be true, drawing from it consequences that I find to be impossible as well as (a) itself.

If by ‘conceiving it to be true’ you mean ‘giving some degree of assent to it, however small’, I concede that I can’t do that. But will you say that every proposition to which I can give any degree of assent is possible? This contradicts experience; so the maxim can’t be true in this sense.

Sometimes when we say ‘I can’t conceive x to be true’ we mean that we judge x to be impossible. Indeed, in this sense I can’t ‘conceive (a) to be true’, because I do judge it to be impossible. But taking the maxim in this sense, it means

•Everything that we judge to be possible is possible.

But doesn’t it often happen that what one man judges to be possible another man judges to be impossible? So the maxim is not true when understood in this way.

I can’t find any other meaning for ‘conceiving a proposition’ or ‘conceiving a proposition to be true’. I don’t know anything that can be meant by ‘having the idea of a proposition’ other than understanding its meaning or judging its truth. I can understand a proposition that is false or impossible as well as one that is true or possible; and I find that men have contradictory judgments about what is possible or impossible as well as about other things. In what sense, then, can it be said that having an idea of a proposition gives certain evidence that it is possible?. . . .

2. Every proposition that is necessarily true stands opposed to a contradictory proposition that is impossible; and someone who conceives either of them conceives both. If you believe that two and three necessarily make five, you must believe it to be impossible that two and three should not make five. You conceive both propositions when you believe one. Every proposition carries its contradictory in its bosom, and both are conceived at the same time. ‘Whenever we dissent from what someone says’, says Hume, ‘we conceive both sides of the question, but we can believe only one side’ (Treatise I.iii.7). From this it certainly follows that when we dissent from any person about a necessary proposition, we conceive one that is impossible; yet I know of no other philosopher who has made as much use as Hume has of •the maxim that whatever we conceive is possible. Many of the specifically Humean doctrines are built on it; and if it is true they must be true. But he didn’t notice that in the passage I have just quoted—a passage that is obviously true—he contradicts •the maxim himself!

3. Mathematicians have proved many things to be possible and others to be impossible; these results wouldn’t have been believed if they hadn’t been demonstrated. But I have never come across a mathematician trying prove something to be possible because it can be conceived or impossible because it can’t be conceived. Why isn’t this maxim invoked to settle whether it is possible to square the circle?—a matter on which eminent mathematicians have disagreed. It is easy to conceive that in the infinite series of numbers and intermediate fractions some one member of the series may have the same ratio to another as the side of a square has to its diagonal; yet this, though conceivable, can be demonstrated to be impossible.

4. Mathematicians often require us to conceive impossible things in order to prove them to be impossible. That is what happens in all their demonstrations ad absurdum. Euclid tells me: Conceive a straight line drawn from one point on the circumference of a circle to another point on that circumference, the line falling outside the circle; I conceive this; I reason from it, until I come to a consequence that is manifestly absurd; and from this I infer that the thing I conceived is impossible.

Having said so much to show that our power of conceiving a proposition is no criterion of its possibility or impossibility, I shall add a few observations on the extent of our knowledge of this kind.

1. There are many propositions which we, using the faculties God has given us, judge to be not only true but necessary. All mathematical propositions are of this kind, and so are many others. The contradictories of such propositions must be impossible. So our knowledge of what is impossible must be at least as extensive as our knowledge of necessary truth.

2. By our senses, by memory, by testimony, and by other means, we know to be true many things that don’t appear to be necessary. But whatever is true is possible. So our knowledge of what is possible must extend at least as far as our knowledge of truth.

3. If someone claims to determine the possibility or impossibility of things beyond these limits, let him bring proof. I don’t say that no such proof can be brought. It has been brought in many cases, especially in mathematics. But I say that his being able to conceive a thing is no proof that it is possible. Mathematics affords many instances of impossibilities in the nature of things which no man would have believed if they—·i.e. the impossibility results·—hadn’t been strictly demonstrated. If we could reason demonstratively in other subjects as extensively as we can in mathematics, we might find many things to be impossible which (·as things are·) we are sure are possible.

‘It is possible that God should have made a universe of sensible and rational creatures into which neither natural nor moral evil should ever enter.’ You may be right, for all I know. But how do you know that it is possible? That you can conceive it, I grant; but that isn’t proof. I can’t admit as an argument, or even as a pressing difficulty, anything based on the supposition that such a thing is possible when •there is no good evidence that it is possible. and •for all we know it may in the nature of things be impossible.

Chapter 4: The train of thought in the mind

[Throughout most of this version of the work, ‘fancy’ has been replaced by ‘imagination’, which means the same thing and is less distracting to us. In this chapter, however, ‘fancy’ will be allow to stand unaltered, for a reason that will soon appear.]

Everyone is conscious of a succession of thoughts that pass through his mind while he is awake, even when they are not aroused by external objects.

The mind can be compared in this to fermenting beer. When it is not in this state, once the beer is still it remains still until some external impulse moves it. But in the state of fermentation it has some cause of motion in itself —a cause which, even when there is no impulse from the outside, won’t let it be still for a moment and produces a constant motion and bubbling. . . .not only of merely intellectual thoughts but also of sentiments, emotions, and affections that come with the thoughts.

Modern philosophers have called this continued succession of thought ‘the imagination’. I think it was formerly called ‘the fancy’ or ‘the phantasy’. If the old name was to be laid aside, I wish it had been replaced by a name less ambiguous than ‘imagination’, which had two or three other meanings as well.

It is often called the ‘train of ideas’. This might lead one to think that it is a train of bare conceptions, but that would surely be a mistake. It is made up of many other operations of mind as well as of conceptions or ‘ideas’.

Memory, judgment, reasoning, emotions, affections, and purposes—in short, every operation of the mind except those of the senses—sometimes occurs as an ingredient in this train of thought. To make the train of our thoughts be only a train of ideas, we would have to take ‘idea’ in a very extended sense. So much for the •name; let us now consider the •thing.

Trains of thought in the mind are of two kinds: some flow spontaneously, like water from a fountain, with no exercise of any governing force to keep them in order; others are regulated and directed by an active and purposive effort of the mind.

These two kinds, however distinct in their nature, are usually mixed together in adults who are awake. •On the one hand, we are rarely so empty of all projects and designs that we let our thoughts go their way without the least check or direction. . . . •On the other hand, when a man is attending with the greatest intensity to some theoretical issue or some practical plan, trying to exclude every thought that isn’t relevant to his present purpose, such thoughts will often rudely •force their way in on him, in spite of his attempts to keep them out, and •occupy by a kind of violence some of the time he had allotted to another purpose. One man may have more control over his thoughts than another man, perhaps more than he himself has at another time. But even in the best trained mind, I believe, the thoughts will sometimes be disobedient, sometimes capricious and self-willed, just when we most want to have them under command.

It has been observed very justly—·e.g. by Malebranche·— that we mustn’t credit the mind with having the power to call up any thought at pleasure. Why? Because voluntarily setting oneself to call up x is an operation that must include the thought of x; so voluntarily calling up a thought would involve already having that thought in one’s mind. Still, it is certainly true that a man has a considerable power in regulating and disposing his own thoughts. Everyone is conscious of this; I can no more doubt it than I can doubt that I think at all.

We seem to treat the thoughts that crowd into the fancy in the way a great man treats those who crowd into a reception that he is giving. They are all eager for his attention; and he goes round the circle bestowing a bow on one, a smile on another; asks a short question of a third, while a fourth is honoured with a private conversation. Most of them receive no particular mark of attention, and go as they came. . . .

Similarly, a number of thoughts present themselves to the fancy spontaneously; but if we pay no attention to them and don’t enter into conversation with them, they pass along out with the rest of the crowd and are immediately forgotten as though they had never appeared. But those we think we should pay attention to can be stopped, examined, and arranged for any particular purpose we have in view.

A train of thought that was at first put together deliberately and with care will present itself spontaneously after it has been often repeated and becomes familiar. Take for example the case of someone who has composed a tune so as to please his own ear; after he has played or sung it often, the notes will arrange themselves in the right order, and he’ll require no effort to regulate their succession.

. . . .Now let us return to the trains of thought that are spontaneous, which must be first in the order of Nature.

[Reid now devotes over three pages to describing the different kinds of daydreams, fantasies etc. that different kinds of people will have—the young politician, the lovesick man, and so on. There is not much of philosophical interest here until we come to this:]

In mature adults even these spontaneous bouts of fancy involve some arrangement of thought; and I think you’ll agree that in those who have the greatest stock of knowledge and the best natural talents even the spontaneous movements of fancy will be the most regular and connected. They have an order, connection, and unity that distinguishes them from the dreams of a sleeper or the ravings of someone in a delirium, just as much as from the finished productions of art.

How is this regular arrangement brought about? It has all the marks of judgment and reason, yet it seems to spring up spontaneously before any judgment is made.

Shall we follow Leibniz in believing that the mind was originally formed like a wound-up watch, and that all its thoughts, purposes, passions, and actions are brought about by the gradual unwinding of the machine’s original spring, and succeed each other in order, as necessarily as the motions and pulsations of a watch?

If a three-year-old child were asked to explain the phenomena of a watch, he would think that the watch contains a little man or some other little animal that beats continually and produces the motion. Of these two,

•the hypothesis of this young philosopher in turning a watch-spring into a man,

•the hypothesis of the German philosopher in turning a man into a watch-spring,

which is the more rational? It is hard to say!

To explain the regularity of our first thoughts in terms of motions of animal spirits, vibrations of nerves, attractions of ideas, or from any other unthinking cause—whether mechanical or contingent—seems equally irrational. [The phrase •‘mechanical or •contingent’ seems to mean •‘resulting from some fairly permanent structure in the person’s make-up or •resulting from a number of co-operating causes that just happened to come together in the person at that time’.]

If we can’t distinguish •the strongest marks of thought and design from •the effects of mechanism or contingency, our situation will be very miserable. For it would follow that we have no evidence of thought in any of our fellow-men— indeed, that we have no evidence of thought or design in the structure and government of the universe. If •one good phrase or sentence was ever produced without any input from a previous judgment, why not •an Iliad or Aeneid? It’s only a difference of degree. . . . No coincidence of unthinking causes could produce a rational train of thought.

So when •a train of thought presents itself spontaneously to a man’s fancy without his having thought about it, it is highly probable—to say the least—that whatever is regular and rational in •it is a copy of something that had previously been composed by the man’s own rational powers or those of someone else.

That is certainly how we judge in similar cases. For example, I find in a book a train of thinking that has the marks of knowledge and judgment. How was it produced?

‘It is printed in a book.’

This answer doesn’t satisfy me, because the book has no knowledge or reason.

‘A printer printed it, and a compositor set the type.’

This doesn’t satisfy me either, because those causes may have known very little about the subject. There must be an earlier cause of the composition.

‘It was printed from a manuscript.’

True. But the manuscript is as ignorant as the printed book.

‘The manuscript was written or dictated by a man of knowledge and judgment.’

This and only this will satisfy a man of ordinary intelligence; and it will appear to any such man extremely ridiculous to believe that such a train of thinking could originally be produced by a cause that doesn’t reason or think.

Whether such a train of thinking is •printed in a book or •printed (so to speak) in his mind and issued spontaneously from his fancy, it must have been composed with judgment by himself or by some other rational being.

We can confirm this, I think, by tracing the progress of the human fancy as far as we can back ·into childhood·. [As Reid is going to say a lot about young children, it may be appropriate to report that he had nine children, and outlived eight of them.]

We don’t have the means for knowing how the fancy is employed in infants. Their time is divided between the use of their senses and sound sleep; so that there is little time left for imagination, and the materials it has to work on are probably very scanty. A few days—sometimes a few hours—after they are born we see them smile in their sleep. But it’s not easy to guess what they are smiling at, for it’s not until some months later that they smile at anything while awake. It is also common to see them move their lips, as if they were sucking, while they are asleep.

These things seem to reveal some working of the imagination, but there’s no reason to think that there is any regular train of thought in the minds of infants.

By a ‘regular’ train of thought I mean one that has a beginning, a middle, and an end—an arrangement of its parts, according to some rule [‘regular’ comes from Latin regula = ‘rule’], or with some intention. For example:

•the conception of a plan and of the means for carrying it out,

•the conception of a whole and of the number and order of the parts.

These are instances of the simplest trains of thought that can be called ‘regular’.

Man undoubtedly has •a power. . . .by which he distinguishes a composition from a heap of ·raw· materials—a house from a heap of stones, for instance, a sentence from a heap of words, a picture from a heap of colours. It seems to me that children don’t have any regular trains of thought until •this power begins to operate. Those who are mentally retarded to such an extent that they never show any signs of •this power also show no signs of regularity of thought. So it seems that •this power is connected with all regular trains of thought, and may be the cause of them.

Such trains of thought show up in children when they about two years old. At that age they can attend to the doings of older children in making their little houses, ships, and so on, in imitation of the works of men. They are then capable of some small understanding of language, which shows both a regular train of thinking and some degree of abstraction. I think we can see that the faculties of children who are two or three years old differ from those of the cleverest brute animals. Children at that age can perceive design and regularity in the works of others, especially those of older children; their little minds are fired with the discovery; they are eager to imitate it, and never at rest till they can exhibit something of the same kind.

When a child first learns by imitation to do something that requires design, how he rejoices! Pythagoras wasn’t happier in the discovery of his famous theorem! The child seems to reflect on himself and to swell with self-esteem. His eyes sparkle. He is impatient to show everyone his performance, and thinks himself entitled to their applause. He is applauded by all, and feels the same emotion from this applause as a Roman Consul did from a triumph. He has now a consciousness of some worth in himself. . . .

As children grow up they are delighted with stories, with childish games, with schemes and plans. Everything of this kind stores the fancy with a new regular train of thought, which becomes familiar by repetition so that one part of it draws the rest after it in the imagination.

The imagination of a child, like the hand of a painter, is long employed in copying the works of others before it attempts any invention of its own. The power of invention hasn’t yet emerged, but it is developing, and like the bud of a tree is ready to split open its outer cover when some casual event helps it to burst out.

No other power of the understanding gives so much pleasure to its owner as invention does—whether it is employed in mechanics, in science, in the conduct of life, in poetry, in wit, or in the fine arts. Someone who is conscious of having the power of invention gets from this a worth and importance in his own eyes that he hadn’t had before. He feels like someone who has been living on hand-outs from others and now has some property of his own. When this power begins to be felt in the young mind, it has the grace of novelty added to its other charms, and it is caressed more than all the rest—like the youngest child of the family!. . . .

The power of invention is less evenly distributed among men than almost any other. When it succeeds in producing something that all mankind care about, we call it ‘genius’, a talent that very few are blessed with. [In Reid’s day, ’genius’ meant something like ‘high-level intellect’; it wasn’t as strong in its meaning as it is today.] But there is perhaps a lower kind—or lower degree—of invention that is more common. Anyway, be that as it may, there is no doubt that the power of invention in those who have it will produce many new regular trains of thought; and when these are expressed in works of art, in writing, or in speech, they will be copied by others.

As soon as children have enough judgment to distinguish what is regular, orderly, and connected from a mere jumble of thoughts, their minds are provided with regular trains of thinking by the following ·two· means.

(1) By copying things that they see other people do and say. Man is the most imitative of all animals: not only does he deliberately imitate what he thinks has any grace or beauty, but also without intention he is led, by a kind of instinct that is hard to resist, into the ways of speaking, thinking, and acting that he has often encountered in his early years. The more children see of what is regular and beautiful in what is presented to them, the more they are led to observe and to imitate it.

This is the chief part of their stock ·of regular trains of thought·; it comes down to them by a kind of tradition from those who came before them; and we shall find that the fancy of most men is stocked with materials from the fancies of people they have conversed with, as well as from their religion, language, and manners.

(2) By adding regular trains of thought that really are theirs. What these amount to will vary from person to person, depending on how much each person has studied and on how inventive he is; but in the bulk of mankind original trains of thought don’t amount to much.

Each profession and each rank in life has a •way of thinking and a •turn of fancy that is special to it (in theatrical comedies and works of humour, profession and rank are identified by •those). The bulk of men of the same nation, of the same rank, and of the same occupation, are cast in the same mould (so to speak). This mould itself changes slowly and gradually through new inventions, influence from outsiders, or other chance happenings.

[Reid goes on at length about how wonderfully practice and habit can enrich one’s stock of regular trains of thought— for example ‘the versatility of imagination that a well bred man acquires by being much exercised in the various scenes of life’, so that he can speak and behave appropriately in a wide variety of social situations. Here is one episode in this discussion:]

When such habits are acquired and perfected, they are exercised without any laborious effort, like the habit of playing on a musical instrument. Countless movements of the fingers on the keys must be directed in one particular train or succession. Only one arrangement of those movements is right, and ten thousand are wrong and would spoil the music. The musician doesn’t give the least thought to those movements; he has a clear idea of the tune and he sets himself to play it. The movements of the fingers arrange themselves so as to achieve what he intends. [He compares that with the performance of a practised speaker on a topic that he knows well. After some more along these lines, Reid (a) sums up this part of his discussion with a clear swipe at the theory of ‘association of ideas’ espoused by Locke and Hume, and (b) starts to introduce a slightly new topic, in the development of which (a) will recur.]

(a) Up to here, I have considered operations of fancy tha teither •are spontaneous or at least •require no laborious effort to guide and direct them, and I have tried to explain the degree of regularity and arrangement that is found even in them. It seems to me that this phenomenon is well enough explained by

•the natural powers of judgment and invention,

•the pleasure that the exercise of those powers always brings,

•the means we have of improving them by imitating others, and

•the effect of practice and habits

—without supposing any unaccountable attractions of ideas by which they arrange themselves!

(b) But we are able to direct our thoughts in a certain course so as to perform a chosen task.

Every work of art has its model formed in the imagination. That is where Homer’s Iliad, Plato’s Republic, and Newton’s Principia were made. Are we to believe that those works spontaneously took the form in which they now appear? That the sentiments, the manners, and the passions arranged themselves, all at once, in the mind of Homer so as to form the Iliad? Was there no more effort in the composition than there is in telling a well-known tale or singing a favourite song? This cannot be believed.

Some ·casual· thought may, through sheer good luck, have first suggested the plan of ‘singing the wrath of Achilles’, but surely it was a matter of judgment and choice where the narrative should begin and where it should end.

No doubt the fertility of the poet’s imagination suggested a variety of rich materials, but wasn’t judgment necessary to select what was proper, to reject what wasn’t, to arrange the materials into a sound composition, and to adapt them to each other and to the design of the whole?

No-one can believe that Homer’s ideas arranged themselves according to the most perfect rules of epic poetry, doing this merely by certain sympathies and antipathies— certain attractions and repulsions—inherent in their natures.

I would find it easier to believe that after he invoked his muse the poet did nothing at all but listen to the song of the goddess! It is true that poets and other artists must make their works appear natural; but •Nature is the perfection of •art, and there can be no sound imitation of Nature without art. When the building is finished, the rubbish, the scaffolding, the tools and engines are carried out of sight; but we know it couldn’t have been built without them.

So the train of thinking can be guided and directed in much the same manner as the horse we ride. The horse has his strength, his agility, and his mettle in himself; he has been taught certain movements and many useful habits that make him more subservient to our purposes and obedient to our will; but to complete a journey he must be directed by the rider.

Similarly, fancy has its original powers, which are very different in different persons; it has more regular movements •to which it has been trained by a long course of discipline and exercise, and •by which it may suddenly and spontaneously and without much effort produce things that have a considerable degree of beauty, regularity, and design.

But the most perfect works of design are never sudden and spontaneous. We look back over our first thoughts, getting at a proper distance from them, examining every part, and taking a complex view of the whole. Our critical faculties enable us to see that this part is redundant, that one deficient; here is a lack of courage, there a lack of delicacy; this is obscure, that is too diffuse. Things are re-organized according to a second and more deliberate judgment—what was lacking is added, what was dislocated is put in joint; redundant passages are lopped off, and the whole thing polished. . . . Nothing that is regular was ever at first conceived without design, attention, and care.

I shall now offer a few reflections on a theory that has been used to explain this successive train of thought in the mind. It was hinted at by Hobbes, but has attracted more attention since it was clearly presented by Hume.

That author thinks that the train of thought in the mind results from a kind of attraction that ideas have for other ideas that relate to them in certain ways. He thinks that the complex ideas that are the common subjects of our thoughts and reasoning result from the same cause. This attraction of ideas, Hume thinks, is produced by these three relations and no others: •causation, •contiguity [= ‘nextness’] in time or place, and •similarity. He asserts that these are the only general sources for the uniting of ideas. And in another place, where he has to take notice of contrariety as a source of connection among ideas, he tries to reconcile this with his system by telling us, solemnly, that contrariety may perhaps be regarded as a mixture of causation and resemblance. As for the status of the supposed truth that

ideas that are related in any of these ways mutually attract each other, so that when one is presented to the fancy the other is drawn along with it

—Hume seems to think that this is an original ·or basic· property of the mind, or rather of the ideas, and therefore can’t be explained ·because explanations have to appeal to something more basic than the thing being explained. I have two observations to make about this theory·.

(1) Although it is true that the thought of any object is apt to lead us to the thought of its cause or effect, of things contiguous to it in time or place, or of things resembling it, this list of the relations that are apt to lead us from one object to another is very inaccurate.

The list is too long, on Hume’s own principles. According to his philosophy, causation implies merely a constant conjunction observed between the cause and the effect; so •contiguity must include •causation, bringing his three sources of attraction down to two.

But actually the list is much too short. Every relation between things has some tendency to lead the thought in a thinking mind from one to the other; and not only every relation but every kind of contrariety and opposition. (Hume’s statement that contrariety can perhaps be considered as a mixture ‘of causation and resemblance’ makes as little sense to me as if he had said that shape can perhaps be considered as a mixture of colour and sound. [Reid is referring to the last footnote of Section 3 of Hume’s Enquiry concerning Human Understanding.]) Our thoughts pass easily

•from the end to the means;

•from any truth to

the evidence on which it is based,

the consequences that follow from it, or

the use that can be made of it;

•from a part to the whole,

•from a subject to its qualities, or

•from related things to the relation.

Such transitions in thinking must have been made thousands of times by everyone who thinks and reasons, thus becoming beaten tracks (as it were) for the imagination. Our train of thinking is influenced by the relations of objects not only

to each other

but also

to the present state of the mind,

to the habits we have acquired, whether moral or intellectual,

to the company we have kept, and

to the occupation in which we have been chiefly employed.

One event will prompt very different thoughts in different persons, and in the same person at different times, depending on whether he is in a good or a bad mood, is lively or dull, angry or pleased, gloomy or cheerful. . . .

(2) Let us consider how far this attraction of ideas can be explained in terms of original qualities of human nature.

I believe the original ·basic· principles of the mind, which we can’t explain except by saying ‘That is how we are built’, are more numerous than is commonly thought. But we ought not to multiply them without necessity. [Reid is echoing Occam’s Razor: Entia non sunt multiplicanda praeter necessitatem—Entities shouldn’t be multiplied beyond necessity.] ·And I think that Hume does multiply them beyond necessity, or at least postulates some that there is no need to postulate·. Trains of thinking that have become familiar through frequent repetition spontaneously present themselves in our fancy—this fact seems to need only one original quality of the mind, namely the power of habit.

In all rational thinking, and in all rational speech— whether serious or merely amusing—each thought must have some relation to what went before. So everyone from the dawn of reason must have been accustomed to sequences of related objects ·of thought·. These please the understanding, and by custom they become like beaten tracks that invite the traveler.

As far as we have the power to direct our thoughts—and we certainly have a great deal of that power—our thoughts will get their direction from the active sources of mental energy that are common to men—our appetites, our passions, our affections, our reason, and our conscience. Everyone will find in his own experience that the trains of thinking in his mind are chiefly governed by whichever of these is prevalent at the given time. And even when someone’s mind is free from every emotion and desire, there will still be some objects that are more acceptable to him than others. The witty man is pleased with surprising similarities or contrasts, the philosopher with relationships that can be reasoned about, the merchant with what tends to profit, and the politician with what may mend the state. . . .

It can’t be denied that the state of the body has an influence on our imagination, depending on whether a man is sober or drunk, fatigued or refreshed. Uncooked food and indigestion are said to cause unpleasant dreams, and probably have a similar effect on the waking thoughts. Opium gives to some people pleasing dreams, and pleasing imaginations when awake, while to others what it gives is horrible and distressing. These influences of the body on the mind can only be known by experience, and I don’t think we can give any explanation for them.

. . . .I believe we are originally disposed to pass, in imagination, from any one object of thought to others that are contiguous to it in time or place. I think this can be seen in brutes and in mentally defective people, as well as in children before they have acquired any habits that might account for it. The sight of •an object is apt to suggest to the imagination things that have seen or felt in conjunction with •it, even when the memory of that conjunction is gone.

Such conjunctions of things influence not only the imagination, but also beliefs and emotions, especially in children and in brutes; and perhaps what we call ‘memory’ in brutes is merely something of this kind.

They expect events to occur in the same order in which they happened before; and this expectation regulates their actions and emotions as well as their thoughts. A horse takes fright at the place where some object frightened it before. We are apt to infer from this that he remembers the former accident; but perhaps it is only an association in his mind between the place and the emotion of fear, without any clear memory. . . .

[The chapter—and thus the Essay—ends with a couple of pages in which Reid: •praises Locke’s chapter on the association of ideas, and says that its examples provide evidence that ideas can be linked not only to ideas but also to emotions; •criticises an aspect of Hume’s treatment of this topic; and writes at some length about the value to you of stocking your imagination with thoughts about good human conduct and, especially, about God.]

Essay 5: Abstraction

Chapter 1: General words

Chapter 2: General conceptions

Chapter 3: General conceptions formed by analysing objects

Chapter 4: General conceptions formed by combination

Chapter 5: Remarks on the names that are given to our general notions

Chapter 6: Opinions of philosophers about universals

Chapter 1: General words

The words we use in language are either •general words or •proper names. Each proper name is intended to signify just one individual. Such are the names of men, kingdoms, provinces, cities, rivers, and of every other creature of God or work of man that we choose to distinguish from all others of the kind by giving it a name of its own. All the other words in language are general—not dedicated to naming some one individual thing, but equally related to many.

Logicians label as ‘general terms’ any general words that can make the subject or the predicate of a proposition. But under my label ‘general words’ I include not only those words but also their auxiliaries,. . . .such as prepositions, conjunctions, and articles, which are all general words though they can’t properly be called general terms. In every language— whether rough or polished—most of the words are general words, and proper names make a very small proportion of the whole. Grammarians have grouped all words into eight or nine classes, known as ‘parts of speech’. All the proper names are found in just one of these groups, namely that of nouns. All adjectives, pronouns, verbs, participles, adverbs, articles, prepositions, conjunctions, and interjections, are general words—and so are most nouns. Every noun that has a plural number is a general word; for no proper name can have a plural number, because it signifies only one individual. In all the fifteen books of Euclid’s Elements every single word is general, and that holds also for many other large volumes.

At the same time it must be acknowledged that all the objects we perceive are individuals. Every object of sense, of memory, or of consciousness is an individual object. All the good things we enjoy or desire, and all the evils we feel or fear, must come from individuals; and I think we can safely say that every creature that God has made anywhere in the universe is an individual.

So how does it come about that in every language general words make the greatest part of the language, and proper names only a very small and inconsiderable part of it?

This seemingly strange phenomenon can, I think, be easily explained by the following ·three· points.

(1) A few individuals that everyone is aware of have proper names in all languages—such as the sun, the moon, the earth, and the sea—but the great majority of the things we choose to give proper names to are local, known perhaps to a village or to a neighbourhood, but unknown to •most people who speak that same language and to •all foreigners. Because the names of such things are confined to a corner, and have no names corresponding to them in other languages, they aren’t regarded as a •part of the language, just as the customs of a particular village aren’t regarded as a •part of the law of the nation.

That is why there are so few proper names belonging to any language. Now let us consider why there must be so many general words in every language.

(2) Every individual object that we encounter has various •attributes, and •they are what make the object useful or harmful to us. We don’t know the essence of any individual object; all we can know about it are its attributes—its quantity, its various qualities, its various relations to other things, its place, its situation and motions.

•The only way we can communicate our knowledge of objects to others is by reporting on their attributes.

•Our hopes or fears relating to objects are governed by their attributes.

•Only by attention to their attributes can we make objects serve our purposes.

Therefore, we give names to such attributes.

Now all attributes must from their nature be expressed by general words, and are so expressed in all languages. In ancient philosophy, attributes in general were called by two names that express their nature: •‘universals’, because they can belong equally to many individuals; •‘predicables’, because whatever is predicated—i.e. affirmed or denied—of one subject could be predicated of others as well, and therefore is a universal and is expressed by a general word. So ‘predicable’ means the same as ‘attribute’. . . . The attributes that we find either in the creatures of God or in the works of men are common to many individuals—we either find that they are or presume that they may be, so we give them the same name in every subject to which they belong.

As well as attributes belonging to individual things there are attributes of attributes, which we could call ‘secondary attributes’, ·distinguishing attributes of individuals by the label ‘primary attributes’·. Most attributes are capable of different degrees and different •modifications, which must be expressed by general words. Thus, being-in-motion is an attribute of many bodies, but motion ·has many •modifications, for example it· can be in countless different directions, can be quick or slow, in a straight line or on a curve, uniform or accelerating or decelerating.

[A note on ‘proposition’ in Essay 4, chapter 3 is applicable here. In what follows, Reid mostly uses ‘proposition’ to mean ‘sentence’, i.e. a bit of language. But he starts by speaking of a ‘proposition we express in language’, and that proposition obviously is not itself a sentence. In this version, ‘proposition’ will be allowed to stand, leaving it to you to resolve its ambiguity case by case.] Because all attributes, whether primary or secondary, are expressed by general words, it follows that in every proposition that we express in language, what is affirmed or denied of the subject of the proposition must be expressed by general words. The subject of the proposition also may often be a general word, as will appear from my next point.

(3) Our ability to distinguish and give names to the different attributes belonging to a single thing goes along with an ability to observe that many things have certain attributes in common while they differ in others. This enables us to put the countless hordes of individuals into a limited number of classes, which are called ‘kinds’ and ‘sorts’—and in the scholastic language are called ‘genera’ and ‘species’.

Observing that many individuals have certain attributes in common, we assign them all to one class, to which we give a name. This class-name includes in its meaning not merely •one attribute but •all the attributes that distinguish that class; and by affirming this name of any individual we affirm it to have all the attributes that characterize the class. Thus men, dogs, horses, elephants, are so many different classes of animals. And we also round up other substances—plants and inanimate things—into classes.

And it’s not only substances that we put into classes in this way. We do the same with qualities, relations, actions, affections, passions, and all other things.

When a class is very large, it is divided into subordinate classes in the same way. The lower class is called a

species or sort of the higher class.

Sometimes a species is again subdivided into subordinate species; and this ·process of· subdivision is carried on as far as we find it convenient for the purposes of language or for the growth of knowledge.

In this classifying of things into genera and species, it is obvious that the name of the species covers more attributes than does the name of the genus. The species includes everything that is in the genus and also the attributes that distinguish this species from others belonging to the same genus. The further down we go with subdivisions, •the more full of meaning the class-names will be, but •the smaller the classes will be. . . . For example, in the series of subordinate general terms

animal

man

Frenchman

Parisian

each term after the first includes in its meaning all that its predecessor includes and more; and each term before the last applies to more individuals than its successor applies to.

Such divisions and subdivisions of things into genera and species, with general names, are not confined to learned and polished languages; they are found in the languages of the most primitive human tribes. This tells us that the invention and the use of general words, to signify both •the attributes that things have and •the genera and species that they fall into, is not a subtle invention of philosophers but rather an operation that all men perform by the light of common sense. Philosophers may theorize in technical ways about this operation. . . .but men of common understanding, without knowing anything of the philosophy of it, can do it; just as they can see objects and make good use of their eyes without knowing anything about the structure of the eye or the theory of vision.

[The examples in the next paragraph are editorial additions, not given by Reid.] Every genus and every species of things can be either the subject or the predicate of a proposition—indeed, of countless propositions; for

Reid writes: every attribute common to the genus or species may be affirmed of it;

examples: mammals (genus) are warm-blooded, have diaphragms, propagate sexually, have skeletons; humans (species) are two-legged, use language, have binocular vision. . .

Reid writes: the genus may be affirmed of every species; and

examples: humans are warm-blooded, have diaphragms, etc., dogs are warm-blooded, have diaphragms, etc., whales are warm-blooded, have diaphragms, etc.

Reid writes: both genus and species may be affirmed of every individual to which it extends.

examples: Joe is warm-blooded etc. and is two-legged etc., Mary is warm-blooded etc. and is two-legged etc.

Thus of man it can be affirmed that •he is an animal made up of body and mind; that •he has a short life that is full of trouble; that •he is capable of various improvements in arts, in knowledge, and in virtue. In short, everything common to the species can be affirmed of man; which is the •subject of all the countless propositions of this sort.

Again it can be affirmed of every nation and tribe, and of every individual of the human race—past, present, or future—that they are men. In all the countless propositions of this sort man is the •predicate of the proposition.

I have remarked that each general term has an extension (·the individuals to which it applies·) and a comprehension (·the attributes that its meaning includes·), and I have noted that in any subdivision of things

•the name of the lowest species is the most comprehensive, and

•the name of the highest genus is the most extensive.

I now point out that such general terms make it possible for propositions also to have an extension and a comprehension. This is one of the grandest powers of language, and fits it for expressing quickly and easily the highest attainments in knowledge of which the human understanding is capable. ·Here is how the comprehension and extension of general terms creates comprehension and extension for propositions·:

•When the predicate is a genus or a species, the proposition is more or less comprehensive according as the predicate is.

Thus, when I say that this coin is gold, by this single proposition I affirm of the coin all the properties that gold is known to have. When I say of any man that he is a mathematician, this label comprehends all the attributes that belong to him as an animal, as a man, and as one who has studied mathematics. When I say that the orbit of the planet Mercury is an ellipsis, I affirm of that orbit all the properties that. . . .geometricians have discovered or may discover concerning ellipses.

•When the subject of a proposition is a genus or a species, the proposition is more or less extensive according as the subject is.

Thus, when I am told that a plane triangle has three angles that are equal to two right angles, this extends to every species of plane triangle, and to every individual plane triangle, that did or does or can exist.

It is by means of such extensive and comprehensive propositions that human knowledge is condensed, as it were, to a size suitable for the capacity of the human mind, adding greatly to its beauty without making it any less clear or any harder to absorb.

General propositions in science can be compared to the seed of a plant which—according to some philosophers—has not only the whole future plant enclosed within it but also the seeds of that plant, the plants that will come from those seeds, and so on through all future generations. But the comparison fails in one respect: whether and when the seed’s contents come into view depends on time and accidents that we don’t control, whereas a general proposition’s contents can be brought out, ripened and exposed to view, whenever we like and in an instant. . . .

What I have said in this chapter is enough, I think, to show that •there can’t be any language—there can’t be so much as a single proposition—without general words, that •they must make the greatest part of every language, and that •it is only by means of them that language can express with wonderful ease and speed all the treasures of human wisdom and knowledge.

Chapter 2: General conceptions

Given that general words are so necessary in language, it is natural to conclude that there must be general conceptions of which they are the signs.

Words are empty sounds when they don’t signify the thoughts of the speaker; and it is only because of signification that they count as general. [Usually Reid’s ‘signification’ = our ‘meaning’, and it has been so presented in this version. But in a context where a word’s ‘signification’ is linked with its ‘signifying’ the speaker’s thoughts, ‘signification’ is left untouched.] Every word that is spoken, considered merely as a sound, is an individual sound. It can be called a general word only because what it signifies is general. Now what it signifies is something conceived by the mind both of the speaker and hearer, if the word has a clear meaning and is clearly understood. So words can’t possibly have a general signification unless the minds of the speaker and of the hearer contain conceptions of things that are general. Those are what I call ‘general conceptions’. Please note that a conception counts as ‘general’ not because there is anything general about the act of the mind in having that conception (for that is an individual act) but because the object—the thing that is conceived—is general.

So our next task is to look into whether we have such general conceptions, and how they are formed.

I start with the conceptions expressed by general terms, i.e. by such general words as may be the subject or the predicate of a proposition. They are either •attributes of things or •genera or species of things.

It is evident, with respect to all the individuals we are acquainted with, that we have a clearer conception of •their attributes than of the •thing that has those attributes.

Take for instance any individual body that we can know: what conception do we form of it? Everyone can answer this from his own consciousness. He will find that he conceives the body as a thing that has length, breadth, and thickness, such-and-such a shape and such-and-such a colour; that it is hard or soft or fluid; that it has such-and-such qualities and is fit for such-and-such purposes. If it is a plant, he may know where it grew, what the form is of its leaves and flower and seed. If it is an animal, he may know what are its natural instincts, its manner of life and of rearing its young. He can surely have a distinct conception of these attributes of this individual, and countless others as well; and he will find words in language by which he can clearly express each of them.

If we consider in this way the conception we form of any individual person whom we know, we shall find it to be made up of various attributes that we ascribe to him—he is the son of x, he is the brother of y, he has such-and-such an employment, has such and such a fortune, is tall or short, well or ill, handsome or ugly, young or old, married or unmarried; and to all this we may add his mood, his character, his abilities, and perhaps some stories about his past.

That is the kind of conception we form of individual persons whom we know. We describe them, to people who don’t know them, through those attributes; which is also how historians give us a conception of the personages of former times. There is no other possible way to do it.

All the distinct knowledge we have or can get of any individual is knowledge of its attributes. For we don’t know the essence of any individual—that seems to be beyond the reach of the human faculties. Now, every attribute is what the ancients called a universal. It is or can be common to various individuals. None of God’s creatures has any attribute that can’t also be had by others, which is why in all languages attributes are expressed by general words.

It also appears from every man’s experience that he can have as clear a conception of attributes like those I have named, and of countless others, as he can have of any individual to which they belong.

Indeed, we don’t clearly conceive anything about an individual except its attributes. It is true that we conceive a subject to which the attributes belong; but we have only an obscure and relative conception of this subject (whether body or mind) when its attributes are set aside .

I noted this before with regard to bodies, in Essay 2 [the opening paragraphs of chapter 19], which you might look back at now; and it is equally obvious with regard to minds. What is it that we call ‘a mind’? It is a thinking, intelligent, active being. Granting that thinking, intelligence, and activity are attributes of mind, I want to know: What is the thing or being that has these attributes? I can find no satisfying answer to this question. We know clearly the attributes of mind and especially its operations, but we have only an obscure notion of the thing itself.

Nature teaches us that thinking and reasoning are attributes that can’t exist without a subject, i.e. with some thing that thinks and reasons; but the best notion we can form of that subject, I believe, implies little more than that it is the subject of such attributes!

Whether other created beings can have knowledge of the real essence of created things, so as to be able to deduce their attributes from their essence and constitution, or whether this is possible only for ·God· who made them, we cannot tell; but it is a knowledge that seems to be quite beyond the reach of the human faculties.

We know the essence of a triangle, and from that essence we can deduce its properties. It is a universal, and could have been conceived by the human mind even if no individual triangle had ever existed. It has only what Locke calls a ‘nominal essence’, expressed in its definition. Every existing thing has a real essence, but it is above our understanding, which is why we can’t deduce its properties or attributes from its nature, as we do with the triangle. In our knowledge of God’s works we must settle for knowing things’ attributes, and believing in a general way that there is a thing to which the attributes belong; this is the opposite direction ·to that of God or Nature, which starts with the thing and lets the attributes flow from that·. . . .

The other class of general terms are those that signify the genera and species into which we divide and subdivide things. And if we can form clear conceptions of attributes, it surely can’t be denied that we can have clear conceptions of genera and species; because they are only collections of attributes that we conceive to exist in a subject and to which we give a general name. If the attributes covered by the meaning of that general name are clearly conceived, the thing meant by the name—·i.e. a certain collection of attributes·—must be clearly conceived. And the name can rightly be applied to every individual that has those attributes.

Thus I conceive clearly what it is to have wings, to be covered with feathers, to lay eggs. Suppose, then, that we give the name ‘bird’ to every animal that has these three attributes. Here undoubtedly my conception of a bird is as clear as my notion of the attributes that are common to this species. And if this is accepted as the definition of ‘bird’, there is nothing I conceive more clearly. If I had never seen a bird but was made to understand the definition, I could easily apply it to every individual of the species, without danger of mistake.

When things are divided and subdivided by men of science, and names are given to the genera and species, those names are defined. Thus the genera and species of plants and of other natural bodies are precisely defined by the writers in the various branches of natural history, so that to all future generations the definition will convey a clear notion of the genus or species defined.

No doubt many words signifying genera and species of things have meanings that are somewhat vague and unclear, so that people speaking the same language don’t always use them in the same sense. But if we attend to the cause of this unclarity, we’ll find that it doesn’t come from •their being general terms, but from •the lack of any authoritative definition of them. Because of this, their meaning has been learned not through a definition but by a kind of induction, by observing which individuals these words are applied to by people who understand the language. We learn by habit to use them as we hear others do, even when we don’t have a precise meaning for them. It can happen that you know that a certain word can properly be applied to this, that, and the other individual, while you are uncertain about whether it is applicable to certain other individuals, your uncertainty coming from there being no good authorities. . . .

Thus a man may know that when he applies the name ‘beast’ to a lion or a tiger, and the name ‘bird’ to an eagle or a turkey, he speaks properly. But he may be uncertain whether a bat is a bird or a beast. If there was any precise and sufficiently authoritative definition of ‘beast’ and of ‘bird’, he wouldn’t be at a loss.

It is said to have sometimes been a matter of dispute, with regard to a mis-shaped offspring of a woman, whether it was human or not. Although this is really a question about the meaning of a word, it may be of some importance because of the privileges that laws have attached to the human character. To make such laws perfectly precise, ‘human’ would have to be defined, and I don’t think that legislators have often, if ever, thought fit to provide such a definition. It is indeed very difficult to settle on a definition of such a common word, and any definition might have unforeseen ·and unwanted· consequences. Since such a definition would seldom be useful, it may be better, when the question arises in a practical way, to leave the meaning of ‘human’ to a judge or jury.

Since a genus or species is a collection of attributes thought of as existing in one subject, a definition ·of the class-name· is the only way to prevent additions to or subtractions from the collection in the conceptions of different persons; and when there is no definition that can be appealed to as a standard, the name will hardly retain the most perfect precision in its meaning.

What I have said makes it obvious, I think, that words signifying genera and species of things often have significations as precise and definite as any words whatsoever; and that when such a word doesn’t have a precise signification, that’s not because it is a general word but for other reasons. Having shown that we can have a perfectly clear conception of the meaning of a general •term, I think we can take it for granted that this also holds for other general •words, such as prepositions, conjunctions, articles. But the point about general terms is enough for my present purpose, which is just to show that we have general conceptions that are at least as clear as our conceptions of individuals. Conceiving the meaning of a general word is the same as conceiving the items that the word signifies. So our conceiving clearly the meanings of general terms is our conceiving clearly that which they signify. What such terms signify is not any individual but rather what is common to many individuals; so we have a clear conception of things that are common to many individuals—that is, we have clear general conceptions.

Beware of the ambiguity of ‘conception’! Sometimes it signifies •the act of the mind in conceiving, sometimes •the thing conceived, the object of that act. If the word is taken in the former sense, I agree that every act of the mind is an individual act; so what is universal is not in the act of the mind but in the object or thing that is conceived. The conceived thing is an attribute common to many subjects, or a genus or species common to many individuals. . . .

Chapter 3: General conceptions formed by analysing objects

Our next topic is the operations of the understanding that enable us to form general conceptions. There seem to me to be three of these:

(1) What philosophers call ‘abstraction’: analysing a subject into its known attributes, and giving to each attribute a name signifying that attribute and nothing more.

(2) What could be called ‘generalising’: observing that one or more such attributes are common to many subjects.

(3) Combining into one whole a certain number of the attributes of which we have formed abstract notions, and giving a name to that combination. That is how we form abstract notions of the genera and species of things.

I shall consider these three operations in order, ·(1) and (2) in this chapter, and (3) in the next·.

Abstraction and generalising—it is hard to say which of them goes first, and perhaps they are so closely connected that neither can claim precedence. For on the one hand (2) to perceive that two or more objects have some attribute in common seems to require nothing more than to compare them. A savage, on seeing snow and chalk, would have no trouble (2) perceiving that they have the same colour. Yet it seems impossible that he should observe this fact about the two objects without (1) abstraction, i.e. separating off in his thought their shared colour from the other qualities in respect of which they differ.

So it seems that we can’t generalise without some degree of abstraction; but I think we can abstract without generalising. Nothing stops me from attending to the whiteness of the page I am writing on without applying that colour to any other object. The ·conception of the· whiteness of this individual page is an (1) abstract conception, but it isn’t a (2) general one until it comes to be applied to more than one individual. Still, ·although abstraction is in a certain way more basic than generalising·, these two operations render service to each other, for the more (1) attributes we observe and distinguish in any one individual, the more (2) resemblances we shall discover between it and other individuals.

With regard to abstraction, strictly so-called, I can’t see anything in it that is difficult either to understand or to do. What can be easier than to distinguish the different attributes that we know to belong to a subject? In a man, for instance, to distinguish his size, his complexion, his age, his fortune, his birth, his profession, and twenty other things that belong to him. To think and speak of these things with understanding is surely within the reach of everyone equipped with the human faculties.

[Reid concedes that a specialist in some field may be able to pick out more attributes of a thing than the rest of us can, but he insists that every human being has ‘a certain degree of this talent’. Then:]

Notice also that attributes that can’t be actually separated •in the subject can quite easily be distinguished and separated •in our conception. Thus in. . . .extension I can distinguish length, breadth, and thickness, yet none of these can be separated from the others. Among the attributes that belong to a subject and are inseparable from it there may be some of which we have no knowledge and consequently no conception; but this doesn’t stop us from conceiving clearly those of its attributes that we do know. For example, all the properties of a circle are inseparable from the nature of a circle, and can be demonstrated from its definition; but a man might have a perfectly clear notion of a circle while knowing very few of the properties of it that mathematicians have demonstrated; and a circle probably has many properties that no mathematician ever dreamed of. . . .

Having considered abstraction strictly so-called, let us next consider the operation of generalising, which is merely observing one or more attributes to be common to many subjects.

Are there attributes that are really common to many individuals? Well, aren’t there many men who are above six feet tall and many shorter than that? Aren’t many men rich and many others poor? Many born in Britain and many born in France? To pile on instances of this kind would be an insult to your understanding. It is certain that there are countless attributes that are really common to many individuals. . . .

There are some attributes expressed by general words of which this may seem more doubtful. . . . This may be said:

Every subject has its own qualities, and the quality belonging to one thing can’t belong to another thing. The whiteness of the sheet of paper that I’m writing on can’t be the whiteness of another sheet, even though both are called ‘white’. The weight of one coin isn’t the weight of another, even if the two are said to ‘have the same weight’.

I answer that •the whiteness of this sheet is one thing, •whiteness is another; the conceptions signified by these two expressions—·‘the whiteness of this sheet’ and ‘whiteness’·— are as different as the expressions. The former signifies an individual quality really existing, and it isn’t a •general conception though it is an •abstract one. The latter, ·’whiteness’·, signifies a •general conception. . . .that can be predicated, always in the same sense, of everything that is white. So if someone said ‘The whiteness of this sheet is the whiteness of that’, everyone would see this to be absurd; but when he says ‘Both these sheets are white’, this is true and perfectly understood. The conception of whiteness doesn’t imply anything about what exists; it would remain the same even if everything white in the universe were annihilated. ·In contrast with that, the conception of the whiteness of this page does imply something about what exists—it implies the existence of this page·.

So we see that the general names of qualities, as well as of other attributes, are applicable in the same sense to many individuals, which couldn’t be so if there weren’t general conceptions signified by such names.

How early in their lives do men begin to form general conceptions? I answer: As soon as a child can say with understanding that he has two brothers or two sisters. As soon as he can use the plural number he must have general conceptions, because no individual can have a plural number.

[Reid has a paragraph about displays of ‘wit’ that consist in the ingenious display of extremely surprising similarities between things. He emphasizes that his principal concern is rather with similarities that ‘can’t escape the notice of the lowest understanding’. Then:]

The ancient philosophers called these items ‘universals’ or ‘predicables’, and tried to group them into five classes:

genus

species

specific difference

properties

accidents.

Lists covering so much territory are seldom complete, so there may well be more classes of universals or attributes ·than are covered in the above list·. Anyway, every attribute common to several individuals can be expressed by a general term, which is the sign of a general conception.

We can see how prone men are to form general conceptions when we look at the use of metaphor and of the other figures of speech based on similarity, i.e. the sharing of attributes. [Reid goes on to comment on the uses of metaphor in literature, on its prevalence in all language-use, on the process through which a foreign word enters a language and is eventually domesticated in it, and the similar process through which a metaphorical expression comes to be regarded as literal. Then:]

Summing up: these two operations of •abstracting and •generalising seems to be common to all men that have understanding. The practice of them must be familiar to everyone who uses language; but it is one thing to practice them and another to explain how they are performed; as it is one thing to see and another to explain how we see. The first is everyone’s business, and is the natural and easy operation of our God-given faculties. The second is the philosophers’ business, and although it isn’t an intrinsically difficult matter it has been severely tangled by •the ambiguity of words and still more by •the hypotheses of philosophers.

·Look at how straightforward and easy it is!· When I consider a billiard ball, its colour is one attribute, which I signify by calling it ‘white’; its shape is another, signified by calling it ‘spherical’; the firm cohesion of its parts is signified by calling it ‘hard’; its recoiling when it strikes a hard body is signified by its being called ‘elastic’; its origin as part of the tusk of an elephant is signified by calling it ‘ivory’; and its use by calling it a ‘billiard ball’.

Each word by which I signify one of those attributes has one distinct meaning, and in this meaning it is applicable to many individuals. It doesn’t signify any individual thing, but an attribute common to many individuals; and a child can understand such words perfectly, and apply them properly to every individual in which they—·or rather the attributes that they signify·—are found.

We acquire our simplest abstract conceptions by analysing a complex object into its several attributes. A chemist isolates the ingredients that make up a compound by analysing the compound. It would be worthwhile to compare these two sorts of analysis. There is such a strong analogy between them that we call them both ‘analysis’; but there is also so much dissimilarity in some respects that we may be led into error by thinking of one in terms that are appropriate only to the other.

Obviously, chemical analysis is a physical operation on portions of matter, using various material instruments. The analysis that is our present topic is purely an operation of the understanding; it requires no material instruments and doesn’t make any change in any external thing. I’ll refer to it as ‘intellectual analysis’ (I could have said ‘mental analysis’).

In chemical analysis, what is analysed is the compound body itself. This is a subject that is so imperfectly known that •it may be made up of a variety of ingredients when to our senses it appears perfectly simple, and •even when we can analyse it into its different ingredients we still don’t know how or why the combination of those ingredients produces that sort of body.

Thus, pure sea-salt is a body that appears as simple as any in Nature. Every least particle of it that our senses can detect is exactly like every other particle in every respect. The most discriminating taste, the most alert eye, can’t pick up any sign of its being made up of different ingredients; yet it can be chemically analysed into an acid and an alkali, and can be produced again by re-combining those two ingredients. But no-one has been able to discover how this combination produces sea-salt. The ingredients are as unlike the compound as any bodies we know. No-one could have guessed in advance that sea-salt is compounded of an acid and an alkali. And that is often the situation regarding the chemical analysis of a compound body.

In the intellectual analysis of an object, obviously, nothing like this can happen, because the thing that is analysed isn’t •an imperfectly known external object, but rather •a conception of the mind itself. And to suppose that a conception contains something that isn’t conceived is a contradiction.

I have a reason for pointing out this difference between the two kinds of analysis. It is that some philosophers, in order to support their systems, have maintained that a complex idea can appear to be perfectly simple and not resemble in any way any of the simple ideas of which it is compounded; just as a white colour can appear perfectly simple and not resemble any of the seven primary colours of which it is compounded, or as a chemical compound can appear perfectly simple and not resemble any of its ingredients.

Those philosophers have inferred from this the important conclusion that a cluster of ideas of sense, properly combined, can make the idea of a mind; and that all the ideas that Locke calls ‘ideas of reflection’ are only compounds made up of the ideas that we have through our five senses. And if

a proper compound of •ideas of matter may make the •idea of a mind,

it is easy to move on from this to the thesis that

a proper compound of •matter itself may make •a mind,

so that a man is only an intricately structured piece of matter.

This strange system rests entirely on the foundation of the thesis that because a compound body may appear to our senses to be perfectly simple, a complex idea that is made up of various simple ideas may appear to be perfectly simple and to bear no signs of its composite nature. On this fundamental proposition of this system I venture to make two remarks.

(1) Even if it were true, it only says that something may be the case. In most cases we are very imperfect judges of what may be, but we do know this much: however certain we are that something may be, this is no good reason for believing that it really is. A ’may be’ is a mere hypothesis, which may provide materials for investigation but isn’t entitled to the least degree of belief. Someone who has a liking for hypotheses will find familiar and easy the shift from what may be to what really is; but for someone who seeks truth without prejudice or prepossession, that shift is a very long and difficult step, and he will never take it unless he has evidence not only that the thing may be but that it really is.

(2) As far as I can judge, this thing that it is said may be actually can’t be! The thesis that

a complex idea is made up of simple ideas in such a way that to a mature understanding reflecting on that idea there will be no appearance of compositeness, and nothing resembling the simple ideas of which the complex idea is made up

—this seems to me to involve a contradiction. The ‘idea’ is a conception of the mind. (If ‘idea’ means anything more than this, I don’t know what it is, and demand •to be told what that meaning is, and •to be given proof that ‘ideas’ in that sense exist.) That the conception of an object should contain anything that isn’t conceived in it seems to me to be as obvious a contradiction as that •there should be an existence that doesn’t exist or that •a thing should be conceived and not conceived at the same time.

But, say these philosophers, a white colour is produced by the composition of the primary colours and yet doesn’t resemble any of them. I grant it. But what can be inferred from this with regard to the composition of ideas? They will have to say that because a white colour is compounded of the primary colours therefore the idea of a white colour is compounded of the ideas of the primary colours. If we allowed this inference we would be landed in countless absurdities. An opaque fluid can be compounded of two or more transparent fluids. Are we to infer that the idea of an opaque fluid can be compounded of the ideas of two or more transparent fluids?

Nature’s way of compounding bodies and our way of compounding ideas are so different in many respects that we can’t reason from one to the other unless it turns out that ideas are combined and analysed by chemical methods. [Reid throws in some technical references to the chemical procedures of his day.] Until this ·fanciful and quite impossible· discovery is made, we must regard as simple the ideas which on the most attentive reflection have no appearance of composition; and regard as ingredients of complex ideas only the ideas which attentive reflection shows us to be contained in them. . . .

Chapter 4: General conceptions formed by combination

Just as by intellectual analysis we form general conceptions of single attributes (which are the simplest of all our conceptions), so by combining several of these into one cluster and giving it a name we form general conceptions that may be very complex and yet very clear. ·Just as we take complexes apart to get simples, so we put simples together to make complexes·. Thus, someone who by analysing extended objects has acquired the simple notions of point line straight curved angle surface solid can easily conceive a plane surface terminated by four equal straight lines meeting at four points at right angles. To this species of shape he gives the name ‘square’. Similarly he can conceive a solid terminated by six equal squares, and give it the name ‘cube’. The words ‘square’ and ‘cube’ and every name of a mathematical figure are general terms, each expressing a complex general conception made by a certain combination of the simple elements into which we analyse extended bodies.

Every mathematical figure is precisely defined by listing •the simple elements of which it is formed and •how they are combined ·in it·. The definition contains the whole essence of it. And every property that belongs to it can be deduced by demonstrative reasoning from its definition. It isn’t a thing that exists, for then it would be an individual. Rather, it is a thing that is conceived without regard to existence.

[Reid reflects on complexes of various kinds: parish, county, kingdom; company, regiment, army; murder, robbery, piracy. Then:]

When we observe that Nature in its animal, vegetable, and inanimate productions has formed many individuals that are alike in many of their qualities and attributes, we are led by natural instinct to expect them to be alike in other respects that we haven’t yet had occasion to perceive. A child who has once burnt his finger in the flame of one candle expects the same outcome if he puts his finger into the flame of another candle, or into any flame; and this leads him to think that all flames have the quality of burning. •This instinctive induction isn’t justified by the rules of logic, and it sometimes leads men into harmless mistakes which experience may correct later on; but •it preserves us from destruction in the countless dangers to which we are exposed.

I call attention here to this driving force in human nature because it adds to the usefulness of the distribution of the productions of Nature into genera and species.

The physician expects that an untested batch of rhubarb will have medical powers like those of rhubarb that he has prescribed on previous occasions. Two lots of rhubarb share certain sensible qualities, and this resemblance is why they are both called by the same general name, ‘rhubarb’. So they are expected to be alike in their medical powers. And as experience has revealed certain powers in one lot, or in many, we presume without experience that every batch of rhubarb that we use will have those same powers.

If a traveler meets a horse, an ox, or a sheep that he never saw before, he isn’t nervous because he believes these animals to be of a species that is tame and inoffensive. But he is afraid of a lion or a tiger because they are of a fierce and ravenous species.

We can get endless advantages, and are exposed to endless dangers, from the various productions of Nature— animal, vegetable, and inanimate. We could live a hundred times as long as we do and still not have enough time to learn from experience the useful and harmful qualities of every individual production of Nature, taken singly.

The author of Nature has provided for our getting such knowledge of his works as is needed for our survival, partly by (1) the constitution of the productions of Nature and partly by (2) the constitution of the human mind.

(1) In the productions of Nature, vast numbers of individuals are made so alike, both in their obvious qualities and in their more hidden ones, that we are not only enabled but (as it were) invited to put them into classes and to give a general name to each class and thus to each of its members. . . .

(2) The human mind is so built that resemblances between individuals in the more obvious qualities on the basis of which we put them into one class naturally lead us to expect that they will be found to be alike also in their less obvious qualities, and usually they are.

So we have a strong and rational inducement to put natural substances into classes—genera and species—under general names, doing this with as much precision and clarity as we can. For the more precisely our divisions are made, and the more clearly the various species are defined, the surer we can be that the qualities we find in one or in a few individuals members of a species will be found in all the rest. . . .

[In an admitted aside, Reid writes of human conceptions that are inventions of the conceiver—a plan for a new kind of machine, a new tune, a new form of government. He stresses how different these ‘works’ are from ‘the works of God’: they are only conceptions, not realities, and we can have a ‘perfect and complete’ knowledge of them, which we can never have of anything created by God. Then he says he will ‘return’ to his proper topic:]

The simple attributes of things that come within our observation are not so numerous that they couldn’t all have names in a rich language. But it would be impossible to give names to all the combinations that can be made of two, three, or more of them. ·Even· the richest languages have names for only a very small proportion of them.

The combinations that have names are nearly, though not completely, the same in the different languages of civilized nations that have relations with one another. So the lexicographer can usually give words in one language that perfectly or nearly correspond to the words in another; and what is written in a simple style in one language can be translated almost word for word into another.

From this we can infer that something disposes men to select, from an infinite number of combinations that might be formed, the same relative few. The ‘something’ is either •certain common drives in human nature or •certain common occurrences in human life.

To explain this phenomenon, Hume appeals to what he calls the associating qualities of ideas—namely causation, contiguity in time and place, and similarity. He says:

Among the things explained by these associating qualities is the fact that languages so nearly correspond to one another; it is because Nature has (in a way) pointed out to everyone the simple ideas that are most suitable for being united into a complex one. (Treatise I.i.4)

I agree with this ingenious author that Nature does in a way point out the simple ideas that are most suitable for uniting into complex ones. But Nature doesn’t do this entirely, or even mainly, by the relations of contiguity, causation, and resemblance amongst simple ideas. Rather, Nature does it through the fitness of the combinations we make to aid our own conceptions and to convey them, easily and agreeably, to others by language. What language is for, and how it works, will lead normally intelligent men to form complex notions that are suitable for expressing their needs, their thoughts, and their desires. And in every language we shall find those to be the complex notions that have names. This explanation makes no appeal to the ‘associating qualities of ideas’ ·on which Hume relied·.

[Reid devotes a page to going through various kinds of human activity, listing for each some of the general terms that are useful in it. He comments on vain or stupid attempts to introduce new general terms that aren’t beautiful or useful, and says that such words don’t last long. Then:]

New inventions of things that are generally useful easily give birth to new notions and new names, which spread as widely as the inventions do. Think of the new complex notions that have been formed, and names for them invented, in the languages of Europe, because of the modern inventions of printing, gunpowder, the mariner’s compass, optical glasses! The simple ideas combined in those complex notions are very ancient, and so are their associating qualities, but they didn’t produce those complex notions until there was a use for them. . . .

What has led men to form and give names to only certain combinations of ideas, neglecting countless other combinations that could be formed, is usefulness and not the associating qualities of the ideas.

[Reid devotes a further page to describing some of the kinds of general terms that we have, and the kinds of ways in which they are useful. He notes with approval Locke’s statement that general terms of ‘mixed modes and relations’—a kind to which many of Reid’s examples belong— are developed by us only because they are useful ‘for the purpose of communicating our thoughts by language’. Then:]

There remains a very large class of complex general terms on which I shall make some comments, I mean the ones we use to name the species, genera, and tribes of natural substances.

Here too it is usefulness that leads us to give general names to the various species of •natural substances; but in combining the attributes that are to be included under the species-name we are more aided and directed by Nature than we are in forming combinations of •mixed modes and relations. In the latter, the ingredients are brought together in everyday events or in the actions or thoughts of men. But in the former—·the complex ideas of natural substances·—the ingredients are united by Nature in many individual substances that God has made. We form a general notion of the attributes that many individuals share. We give a species-name to this combination—a name that applies to all actual and possible substances having those attributes. The species-name includes exactly the attributes—neither more nor fewer—that we see fit to put into its definition. It doesn’t include time or place or even existence, although there can’t be an individual without these.

This work of the understanding is absolutely necessary for speaking intelligibly about the productions of Nature, and for getting benefits and avoiding harm from them. There are so many individuals that it would be beyond the power of language to give a proper name to each of them. If a good or bad quality was observed in an individual, this observation would be almost useless unless there were a species in which the same quality might be expected.

Without some general knowledge of the qualities of natural substances, human life could not be preserved. And we can’t have general knowledge of this kind without grouping things into species under species-names. That is why even among the most primitive nations we find names for fire, water, earth, air, mountains, fountains, rivers; and for the kinds of plants they use, the animals they hunt or domesticate or find useful or harmful. . . .

As the knowledge of Nature advances, more species of natural substances are observed and their useful qualities discovered. For this important part of human knowledge to be communicated and handed down to future generations, it isn’t enough that the species have names; the names need accepted definitions, because otherwise, in the fluctuating state of language, a general name wouldn’t always retain the same precise meaning.

There was undoubtedly a great fund of natural knowledge among the Greeks and Romans in ancient times. There is a great fund of it in Pliny’s natural history; but much of it is lost to us, partly because we don’t always know what species of substance he signifies by a given name. . . .

To prevent such losses in future times, modern philosophers have—to their credit—tried to give names and precise definitions for all the known species of substances with which God in his generosity has enriched our planet. . . . Every species that is known to exist ought to have a name, which should be defined by whatever attributes will serve best to distinguish that species from all others. Nature invites us to do this work, by forming things in such a way as to make the work both easy and important. ·Its importance can be seen in its three stages·:

(1) We perceive many individual substances to be so alike in their •obvious qualities that even the least developed tribes of men consider them as belonging to one species, and give them one common name.

(2) The individuals of a species are generally alike in respect of their •less obvious qualities. So when such a quality is found by observation or experiment in a few individuals of a species, it is presumed and commonly found to belong to the species as a whole. This enables us to draw general conclusions from particular facts. This kind of induction is indeed the master-key to the knowledge of Nature. Without it we couldn’t form any general conclusions in that branch of philosophy.

(3) Simply because of the way we are built, we are led without reasoning to ascribe to the whole species what we have found to belong to individual members of it. This is how we come to know that fire burns and water drowns, that bodies gravitate and bread nourishes.

The species of two of the kingdoms of Nature—namely the animal and vegetable kingdoms—seem to be fixed by Nature through the power they have of reproducing their like. And in these kingdoms men at all times and places have counted the parent and the offspring as belonging to the same species. There are only minor disagreements among naturalists with regard to the species of these two kingdoms; the disagreements may arise from changes produced by soil, climate, and nutrition, and sometimes by monstrous productions [= ‘births of severely misshapen offspring’], which are comparatively rare.

In the inanimate kingdom we don’t have the same means for dividing things into species, and that makes the limits of their species seem more arbitrary. But the progress already made gives us grounds for hope that even in this kingdom, as the knowledge of it advances, the various species may come to be well enough distinguished and defined to serve every purpose that matters.

When the species are so numerous as to burden the memory, it is greatly assisted by grouping them into •genera, the genera into •tribes, the tribes into •orders, and the orders into •classes. Such a regular classification of natural substances by divisions and subdivisions is called a ‘system’. It isn’t a system of •truths, but a system of •general terms with their definitions. . . .

[Reid closes out this chapter with two pages concerning systems of classificatory terms. They deserve respect, he says, as indispensable aids to natural philosophy, but they are only aids—they aren’t the real thing. There is something attractive about them, he adds. ‘There is an intrinsic beauty in arrangement’—he contrasts the appearance of •an army drawn up in ranks for battle with that of •the very same men crowded into a market. His use, above, of ‘class’ as a technical term at the top of a hierarchy— class/order/tribe/genus/species—won’t occur again in this version of the work.]

Chapter 5: Remarks on the names that are given to our general notions

. . . .The names that modern philosophers have given to our general notions have helped to darken our thoughts about them and to make them difficult and abstruse.

We call them ‘general notions’, ‘conceptions’, ‘ideas’. The words ‘notion’ and ‘conception’ in their proper and most common sense signify the •act or operation of the mind in conceiving an object. They’re sometimes used, in a figurative sense, to stand for •the object that is conceived. I don’t think they are often (if at all) used in this figurative sense except when we are speaking of what we call ‘general notions’ or ‘general conceptions’. (All this applies also to ‘idea’ as it is used these days.)

When we describe our ‘notions’ or ‘conceptions’ as general, we have to be using those words in their figurative sense. If we were using them in their proper, literal sense we would be describing as general an act of the mind, and that would be absurd because every act of the mind is an individual act—a particular past or present event. The only generality that is involved is in the object that is conceived, not in the act of conceiving it. We have the power to conceive things that don’t and never did exist, and to conceive attributes without regard to whether anything has them. The conception of such an attribute is an individual act of the mind, but the conceived attribute is common to many actual or possible individuals. We are too apt to muddle •an object of conception with •the conception of that object;’ and the risk of that must increase when the object of conception is itself called a ‘conception’!

The Aristotelians called such objects of conception ‘universals’ and ‘predicables’. Those names had no ambiguity, and I think were much more fit to express what was meant by them than the names we use ·these days·.

That is why I have so often used the word ‘attribute’, which means the same as ‘predicable’. And why I have thought it necessary to keep warning you that when I go along with ordinary usage in speaking of ‘general notions’ or ‘general conceptions’, I always mean things that are conceived and not the mind’s act in conceiving them.

The Pythagoreans and Platonists gave the name ‘ideas’ to such general objects of conception and to nothing else. As we borrowed the •word ‘idea’ from them, so that it is now familiar in all the languages of Europe, I think it would have been a good thing if we had also borrowed their •meaning for it, using it only to signify what they meant by it. We need an unambiguous word to distinguish •things barely conceived from •things that exist. If ‘idea’ had been used only for this purpose, it would have been restored to its original meaning, and that need would have been met.

We can accept the Platonists’ •meaning for ‘idea’ without adopting their •theory about ideas—i.e. without believing that ideas are eternal and self-existent and have a more real existence than the things we see and feel.

What led them to ascribe existence to ideas was the common prejudice that every object of conception must really exist; and having once given existence to ideas, the rest of their mysterious system about ideas smoothly followed. ·Much of their theory was correct·; it’s true that things that are merely conceived

•don’t begin or end,

•aren’t in time or at any place,

•don’t undergo change, and

•are the patterns and exemplars according to which God made everything that he made;

for the work must be conceived by the worker before it is made.

These are undeniable attributes of the ideas of Plato; if we add to them the attribute of real existence, we have the whole mysterious system. Take away the attribute of existence, and suppose ideas to be not •things that exist but •things that are barely conceived, and all the mystery is removed; all that remains is acceptable to the human understanding.

The word ‘essence’ came to be much used among the schoolmen, and what the Platonists called the ‘idea’ of a species they called its ‘essence’. . . . The essences of things were held by the schoolmen to be uncreated, eternal, and unchanging.

Locke distinguishes two kinds of essence—real and nominal. By the ‘real essence’ he means

•the constitution of an individual that makes it be what it is.

This essence must begin and end with the individual whose essence it is; so it isn’t a Platonic idea. But what Locke calls the ‘nominal essence’ is

•the constitution of a species, or what makes an individual belong to that species;

and this is merely the combination of attributes that is signified by the species-name and that we conceive without regard to existence. So the essence of a species is what the Platonists called the ‘idea’ of the species.

If ‘idea’ is restricted to the meaning the Platonists and Pythagoreans gave it, many things that Locke said about ideas will be sound and true, and others will not.

It will be true that most words (indeed all general words) are the signs of ideas, while proper names are not because they signify individual things and not ideas. It will be true not only that there are general and abstract ideas but that all ideas are general and abstract. But it will not be true that •all our simple ideas are acquired immediately either from sensation or from consciousness. Indeed, this is so far from true that in fact •no simple idea is acquired in either of those ways without the co-operation of other powers. The objects of sense, of memory, and of consciousness are not ideas but individuals; for us to have simple ideas those objects must be analysed by the understanding into their simple ingredients. . . . It will be probable not only that brutes have no abstract ideas but that they have no ideas at all. . . .

From all I have said about abstract and general conceptions I think we can draw the following conclusions:

(1) Abstraction is what provides the mind with all its simplest and clearest notions. The simplest objects of sense appear both complex and unclear until by abstraction they are analysed into their simpler elements; and the same holds for the objects of memory and of consciousness.

(2) Our clearest complex notions are the ones formed by compounding the simple notions acquired through abstraction.

(3) Without the powers of abstracting and generalising we couldn’t manage things in an orderly and methodical way by classifying them into genera and species.

(4) Without those powers there could be no definition; for definition can only be applied to universals—no individual can be defined.

(5) Without abstract and general notions there couldn’t be any reasoning or any language.

(6) Because brute animals show no signs of being able •to distinguish the various attributes of the same subject, •to group things into genera and species, •to define, •to reason, or •to communicate their thoughts by artificial signs as men do, I have to agree with Locke that they don’t have the powers of abstracting and generalising, and that this is one way in which Nature has made a specific difference between them and the human species.

Chapter 6: Opinions of philosophers about universals

In ancient philosophy the doctrine of universals—i.e. of things that we express by general terms—looms large. The ‘ideas’ of the Pythagoreans and Platonists, about which I have already said so much, were universals. All science has universals as its object. It was thought that a science must have as its object something real and unchanging; and therefore those who paid homage to truth and science maintained that ideas or universals have a real and unchanging existence. [It this paragraph, and later in this chapter, ‘science’ is used in an old sense in which it means something like ‘body of doctrine that is theoretically highly organized, deductively interconnected, and rigorously proved’.]

The sceptics, on the other hand (for there were sceptical philosophers in those early days), maintained that all things change and are in a perpetual flux; from which they inferred that there is no science, no truth—only uncertain opinion.

Plato and his masters of the Pythagorean school conceded this with regard to •objects of the senses, agreeing that there could be no science or certain knowledge concerning them. But they held that there are •objects of the intellect that are intrinsically superior ·to the objects of the senses·, and belong higher up in the clssification system; and they regarded them as permanent and unchanging. These are ‘ideas’ or ‘universal natures’, of which the objects of the senses are only the images and shadows. To these ideas they ascribed. . . .the most magnificent attributes. They believed that

•for any species of thing—men, roses, circles, etc.— there is one ‘idea’ or ‘form’, which existed from eternity before any individual of the species was formed;

•this idea is the exemplar or pattern according to which God constructed the individuals of the species;

•every individual of the species ‘participates in’ this idea, which is its essence; and

•this idea is also an object of the human intellect when by abstraction we identify it as the same in all the individuals of the species.

Thus the idea of each species, though it is one item and doesn’t change, can be considered in three different views or respects: (1) as having an eternal existence before there was any individual of the species; (2) as existing in every individual of that species without being divided or multiplied, and constituting the essence of the species; and (3) as an object of intellect and of science in man. That is the doctrine of Plato, as far as I can understand it.

His disciple Aristotle rejected (1) as visionary, but fairly much agreed with his master concerning (2) and (3). He didn’t admit (1) the existence of universal natures antecedent to the existence of individuals; but he held that every individual consists of matter and form (I take his ‘form’ to be Plato’s ‘idea’), and that (2) the form is common to all the individuals of the species, and that (3) the human intellect is fitted to receive the forms of things as objects of contemplation. Such are the deep theories about the nature of universals that we find even in the first ages of philosophy. I wish I could make them more intelligible to myself and to you.

The division of universals into five classes—genus, species, specific difference, property, accident—is also very ancient. I think it was borrowed by the Aristotelians from the Pythagorean school.

Porphyry has given us a very clear treatise on these classes, as an introduction to Aristotle’s categories. But he has omitted the intricate metaphysical questions that were debated concerning their nature: Do genera and species really exist in Nature or are they only conceptions of the human mind? If they exist in Nature, are they material or immaterial? And are they inherent in the objects of sense or separate from them? Porphyry tells us that he omits these questions for brevity’s sake, because they are very profound and require precise discussion. The questions probably exercised the minds of the philosophers until about the twelfth century.

At about that time Roscelin, the master of the famous Abelard, introduced a new doctrine—namely that there is nothing universal but words or names. For this and other heresies he was much persecuted. However, through his eloquence and abilities and those of his disciple Abelard the doctrine spread, and those who followed it were called ‘nominalists’ [from Latin nomen = ‘name’]. His opponents, who held that there are things that are really universal, were called ‘realists’. From the beginning of the twelfth century the scholastic philosophers were divided into these two sects. A few took a middle road between the contending parties: they held that universals are not in •things themselves (as the realists thought), or in •names only (as the nominalists thought), but in •our conceptions. So they were called ‘conceptualists’. But being exposed to the cannons of both the opposing parties, they didn’t put up much of a show.

When the sect of nominalists seemed to be near to dying out, it received new life and spirit from Occam, the disciple of Duns Scotus in the fourteenth century. At that time the dispute about universals in things was revived with the greatest animosity in the colleges of Britain, France, and Germany. It was conducted not only by arguments but also by bitter reproaches, blows, and bloody dog-fights, until the doctrines of Luther and the other ·religious· reformers turned the learned world’s attention to more important subjects.

After the revival of learning, Hobbes adopted the opinion of the nominalists. ‘It is obvious,’ he says, ‘that there is nothing universal but names’ (Human Nature, xii.6). Also: ‘The only universal things in the world are merely names. . . . A proper name brings to mind only one thing, universals recall any one of many’ (Leviathan I.4).

I think Locke can be classified as a conceptualist. He maintained not •that there are things that are universal, but •that we have general or universal ideas which we form by abstraction; and he thinks that this power of forming abstract and general ideas is what chiefly marks us off, intellectually, from the brutes.

Locke’s doctrine about abstraction has been combated by two very powerful antagonists, Berkeley and Hume, who have taken up the opinion of the nominalists. Berkeley thinks that

The theory that the mind has a power of forming abstract ideas or notions of things has played a large part in making people’s theories complex and confusing, and has caused endless errors and difficulties in most branches of knowledge. (6)

Abstract ideas are like a fine and delicate net, which has miserably perplexed and entangled the minds of men (with this special feature: the more sharp-witted and exploratory any man’s mind is, the more completely he is likely to be trapped and held by the net!). (22)

Among all the false principles that people have accepted, none has had a wider influence over the thoughts of enquiring and theory-building men than this doctrine of abstract general ideas. (17)

In twenty-four pages of the Introduction to his Principles of Human Knowledge, Berkeley tackles this doctrine with a zeal proportioned to his sense of its malignant and extensive influence. [The above numerical references, and all remaining references to Berkeley in this chapter, are to sections of that Introduction.]

That the zeal of the •sceptical philosopher (Hume) against abstract ideas was almost equal to that of the •bishop (Berkeley) appears from this:

An important question has been raised about abstract or general ideas, namely: Are they general or particular in the mind’s conception of them? A great philosopher (he means Dr Berkeley) has challenged the usual opinion about this, and has asserted that a general idea is nothing but a particular idea attached to a certain word that gives it a wider application and makes it recall (when needed) other individuals that are similar to it. As I regard this as one of the greatest and most valuable scholarly discoveries that has been made in recent years, I shall try here to confirm it by some arguments that I hope will put it beyond all doubt and controversy. (Treatise I.i.7)

I shall conclude my treatment of this subject with some reflections on what these two eminent philosophers have said about it. [There will be five of them, occupying about ten pages.]

(1) I don’t think we can properly be said to have abstract and general ideas, either in the popular or in the philosophical sense of ‘idea’. In the •popular sense, an idea is a thought; it is an act of the mind in thinking or conceiving any object. This act of the mind is always an individual act—·a particular event, occurring in a particular mind at a particular time·—and therefore there can’t be any general ‘ideas’ in this sense. In the •philosophical sense, an idea is an image in the mind or in the brain, which is the immediate object of thought in Locke’s system, and the only object of thought in Berkeley’s and Hume’s. I believe that there aren’t any ideas of this kind, and therefore there aren’t any abstract general ideas. Indeed, if there really were such images in the mind or in the brain, they couldn’t be general, because everything that really exists is an individual. Universals are not acts of the mind or images in the mind.

So there are no general ideas, in either of the senses in which ‘idea’ is used by the moderns, and that gives Berkeley and Hume an advantage over Locke in this debate. Their arguments against him are good ad hominem [Latin = ‘against the man’; i.e. they have good arguments to show why Locke in particular, given his other views, isn’t entitled to hold that there are general ideas]. They saw further than he did into the real consequences of the hypothesis about ideas that they shared with him, and they reasoned soundly when they concluded from this hypothesis that there is •no material world and •no such power in the human mind as that of abstraction.

A triangle in general, or any other universal, might be called an ‘idea’ by a Platonist; but understanding ‘idea’ as modern philosophers do, it is not an idea; and we never ascribe to ideas the properties of triangles. No idea is ever said to have three sides and three angles. We don’t speak of equilateral, isosceles, or scalene ideas, or of right-angled, acute-angled or obtuse-angled ideas. And if ideas don’t have these attributes, it follows that a triangle is not an idea. The same reasoning can be applied to every other universal.

Ideas are said to have a real existence in the mind, at least, while we think of them; but universals have no real existence. When we ascribe existence to them, it is not existence in time or place but existence in some individual subject; and all that this existence means is that they are truly attributes of such a subject. Their existence is merely predicability, i.e. the capacity to be attributed to a subject. The name ‘predicables’ that was given them in ancient philosophy is the one that best expresses their nature.

(2) I think it must be granted that universals can’t be the objects of imagination, when we take that word in its strict and proper sense. Berkeley writes:

I find that I do indeed have a capacity for imagining— representing to myself the ideas of particular things that I have perceived—and of splitting those ideas up and re-assembling them in various ways. I can imagine a man with two heads, or the upper parts of a man joined to the body of a horse. I can consider the hand, the eye, the nose, each by itself abstracted or separated from the rest of the body. But then whatever hand or eye I imagine must have some particular shape and colour. Similarly, any idea that I form of a man must be of a specific kind of man: he must be white or black or brown, straight or crooked, tall or short or middling. (10)

I think you will find in yourself what this ingenious author found ·in himself ·, namely an inability to imagine a man without colour or height or shape.

As I have already remarked, ‘imagination’ properly signifies a conception of how an object would look if it were actually seen. A universal is not an object of any external sense, so it can’t be imagined; but it can be distinctly conceived. When Pope writes ‘The proper study of mankind is man’, I clearly conceive his meaning, though I don’t imagine a black or a white man, or a crooked or a straight one. The distinction between •conception and •imagination is real, although too often it is overlooked and the words are taken to be synonymous. I can conceive a thing that is impossible, but I cannot clearly imagine a thing that is impossible. I can conceive a proposition, or a demonstration, but I can’t imagine either of them. I can conceive understanding and will, virtue and vice, and other attributes of mind, but I can’t imagine them. Similarly, I can clearly conceive universals but I can’t imagine them.

How do we conceive universals? I admit that I don’t know. I don’t know how I hear or see or remember, and I’m just as far from knowing how I conceive things that don’t exist. In all our original faculties, the structure and manner of operation seems to be beyond our comprehension, and perhaps is perfectly understood only by God who made them.

But when we are conscious of some fact ·about ourselves·, we ought not to deny it just because we don’t know how it is brought about. And I think ·we do know one negative fact about how we conceive universals·: we can be certain that universals are not conceived by means of images of them in our minds, because there can’t be an image of a universal.

(3) It seems to me that on this question Locke and his two antagonists divided the truth between them. He saw very clearly that the power of forming abstract and general conceptions is one of the most distinguishing powers of the human mind, and puts a specific difference between men and brute animals. But he didn’t see that this power is flatly inconsistent with his doctrine concerning ideas.

His opponents saw this inconsistency; but instead of rejecting the hypothesis of ideas they explained away the power of abstraction, leaving no specific distinction between our understanding and that of the brutes.

(4) In his reasoning against abstract general ideas, Berkeley seems to grant, unwillingly or incautiously, all that is needed to support abstract and general conceptions:

I don’t deny that a man can abstract, in that he can consider a figure merely as triangular without attending to the particular qualities of the angles or relations of the sides. But that doesn’t show that he can form an abstract general inconsistent idea of a triangle. (16)

If a man can ‘consider a figure merely as triangular’, he must have some conception of this object of his consideration, for no-one can consider a thing without conceiving it. So he has a conception of a triangular shape, merely as such. I don’t know of anything more that is meant by an ‘abstract general conception of a triangle’.

Someone who considers a figure ‘merely as triangular’ must understand what is meant by ‘triangular’. If to the conception he associates with this word he adds any particular quality of angles or relation of sides, ·this shows that· he misunderstands it and doesn’t consider the figure ‘merely as triangular’. This, I think, clearly shows that someone who considers a shape ‘merely as triangular’ must have the conception of a triangle, abstracting from any quality of angles or relation of sides.

In a similar concession, Berkeley writes: ‘Because all that is perceived is not considered, we can think about Peter considered as a man, or considered as an animal, without forming the abstract idea of man or of animal’ (16 again). I remark that someone who considers Peter as a man or as an animal must conceive the meaning of the abstract general words ‘man’ and ‘animal’; and someone who conceives the meaning of such a word has an abstract general conception.

From these concessions one would be apt to infer that Berkeley thinks that we •can abstract but we •can’t make abstract ideas; and in this I would agree with him. But I can’t reconcile his concessions ·quoted above· with his previously stated general principle: ‘I deny that I can abstract from one another, or conceive separately, qualities that couldn’t possibly exist separately’ (10). This strikes me as inconsistent with the concessions quoted above, and inconsistent with experience.

If we can consider a figure ‘merely as triangular’, without attending to the particular quality of the angles or relation of the sides, this (I think) is conceiving separately things that couldn’t exist separately. For surely a triangle can’t exist without a particular quality of angles and relation of sides. And we know from experience that a man can have a clear conception of a triangle without having any conception or knowledge of many of the properties without which a triangle cannot exist.

Let us next consider Berkeley’s notion of generalising. He doesn’t absolutely deny that there are general ideas—only that there are abstract general ideas. He writes:

An idea, which considered in itself is particular, becomes general in its meaning by being made to represent or stand for all other particular ideas of the same •sort as itself. Suppose for example that a geometrician, proving the validity of a procedure for cutting a line in two equal parts, draws a black line one inch long. As used in this geometrical proof, this particular line is general in its significance because it is used to represent all particular lines, so that what is proved regarding it is proved regarding all lines. And just as that particular line becomes general by being used as a sign, so the word ‘line’—which in itself is particular—is used as a sign with a general meaning. (12)

Here I would remark that when a particular idea is made to be a sign to represent and stand for all things of a •sort, this presupposes that things have been grouped into sorts or species. To be ‘of a sort’ implies having the attributes that characterise the sort and are common to all the individuals belonging to it. So there can’t be a sort without general attributes, and there can’t be any conception of a sort without a conception of the general attributes that distinguish it. So the conception of a sort is an abstract general conception. . . .

When I demonstrate any general property of a triangle, such as that the three angles are equal to two right angles, I must understand or conceive distinctly what is common to all triangles. I must distinguish •the attributes that all triangles have in common from •the attributes that some triangles have and others don’t. And if I clearly conceive what is common to all triangles, without mixing it up with what is not common to them all, this is to form a general conception of a triangle. Without this, one can’t know that the demonstration extends to all triangles.

Berkeley takes special notice of this argument, and answers it thus:

Although the idea I have in view while I make the demonstration may be (for instance) that of an isosceles right-angled triangle whose sides are of a determinate length, I can still be certain that it applies also to all other triangles, no matter what their sort or size. I can be sure of this because neither the right angle nor the equality of sides nor length of the sides has any role in the demonstration. (16)

But if in the idea he has in view he doesn’t clearly distinguish what is common to all triangles from what is not, he couldn’t tell whether something that isn’t common to all has a role in the demonstration. So, to perceive that the demonstration applies to all triangles he has to have a clear conception of what is common to all triangles, excluding from that conception everything that is not common to them all. And that’s all that I understand by ‘an abstract general conception of a triangle’.

[Reid says that Berkeley gets an argumentative advantage from Locke’s having exaggerated how difficult it is to form abstract general ideas, and the hard work and skill needed for that purpose. According to Reid, some are hard to form but many are not—the easy ones include ones that are involved in the earliest and most minimal uses of language. He winds up the discussion thus:] ‘Isn’t it a hard thing,’ Berkeley writes, ‘that a couple of children can’t chatter about sugar-plums and toys until they have first tacked together countless inconsistencies and so formed abstract general ideas in their minds, attaching them to every common name they make use of?’ (14) However ‘hard’ a thing it may be, it is obviously true that a couple of children cannot chatter so as to understand and be understood, even about their sugar-plums and their toys, until they have learned to conceive the meanings of many general words—and this, I think, is to have general conceptions.

(5) Having considered Berkeley’s views on this subject, let us next attend to those of Hume as they are expressed in his Treatise I.i.7. [All indented passages in the rest of this chapter will be quotations from that section of Hume’s.] He entirely agrees with Berkeley:

•A general idea is nothing but a particular idea attached to a certain word that gives it a wider application and makes it recall (when needed) other individuals that resemble it.

•A particular idea becomes general by being attached to a general term, i.e. to a term that is related by a customary conjunction to many other particular ideas which it readily recalls in the imagination.

•Abstract ideas are in themselves individual, even when they become general in their representation. The image in the mind is only that of a particular object, though the application of it in our reasoning may be the same as if it were universal.

Although Hume looks on this as ‘one of the greatest and most valuable scholarly discoveries that has been made in recent years’, it seems to me to be simply the nominalist view that was so much in dispute from the beginning of the twelfth century down to the reformation, and was later supported by Hobbes. I shall briefly consider the arguments that Hume hopes will ‘put it beyond all doubt and controversy’.

He tries to prove by three arguments that it is utterly impossible to conceive any quantity or quality without forming a precise notion of its degrees. This is indeed a great undertaking; but even if he could prove it, it isn’t sufficient for his purpose. There are two reasons why it isn’t.

(a) There are many attributes of things besides quantity and quality, and Hume needs to prove that it is impossible to conceive any attribute without forming a precise notion of its degree. Each of Aristotle’s ten categories is a genus, and can be an attribute; if Hume proved that there can be no general conception of two of them—namely quantity and quality—he still has to prove it of the other eight.

(b) Even if it were impossible to conceive any quantityor quality without forming a precise notion of its degree, it doesn’t follow that it is impossible to have a general conception of quantity and quality. The conception of one pound weight is the conception of a quantity, and of its precise degree; but it is nevertheless an abstract general conception, because it can be the attribute of many individual bodies and of many kinds of bodies. So Hume needs to prove that we can’t conceive quantity or quality or any other attribute without joining it inseparably to some individual subject. [The idea is that if he could prove that, Hume could argue that you can’t conceive one pound weight without conceiving some particular thing having that weight, and he would maintain that in conceiving that thing you conceive it in all its detail.]

This won’t be easy to prove! For instance, I conceive what is meant by ‘a Japanese’ as clearly as what is meant by ‘an Englishman’ or ‘a Frenchman’. It is true that being Japanese is not a quantity or a quality, but it is an attribute common to every individual of a populous nation. If I can trust my consciousness, the general term ‘Japanese’ doesn’t lead me to imagine one individual Japanese person as a representative of all others. ·Indeed, it couldn’t do so, because· I have never seen an individual Japanese person.

Thus, although Hume undertakes a large task, even if he succeeded in proving all that he says he will prove, that would be far from sufficient to show that we have no abstract general conceptions. But now let’s let that go, and attend to his arguments for proving this extraordinary thesis that it is impossible to conceive any quantity or quality without forming a precise notion of its degree.

First argument: It is that it’s impossible to distinguish things that are not actually separable. ‘The precise length of a line is not different or distinguishable from the line.’ I have already tried to show that things that can’t be separated in their nature may still be distinguished in our conception. And to be convinced of this look at Hume’s own example! The precise length of a line, he says, is not distinguishable from the line. When I say ‘This is a line’ I say and mean one thing; when I say ‘This is a line three inches long’ I say and mean another thing. If that isn’t distinguishing the length of the line from the line, I don’t know what distinguishing is!

Second argument: ‘Every object of sense, i.e. every impression, is an individual with determinate degrees of quantity and quality. But whatever is true of the impression is true of the idea, because they differ only in their strength and liveliness.’

The conclusion of this argument is indeed validly inferred from the premises. If it is true that ideas differ from objects of sense only in strength and liveliness, as it must be granted that all the •objects of sense are individuals, it will certainly follow that all •ideas are individuals. Granting the validity of this inference, I venture to draw two other conclusions that will follow just as necessarily from the same premises .

(a) If •ideas differ from •objects of sense only in strength and liveliness, it will follow that the •idea of a lion is a •less strong and lively lion. An urgent question arises: can the idea of a lion tear apart and eat the ideas of sheep, oxen, and horses—and even of men women and children?

(b) If ideas differ only in strength and liveliness from theobjects of sense, it will follow that •objects merely conceived are not •ideas; because •objects merely conceived differ from •objects of sense in respects utterly different from strength and liveliness. Every object of sense must have a real existence and time and place. But things merely conceived needn’t have existence or time or place; so even if there were no abstract ideas, it doesn’t follow that abstract and general things can’t be conceived.

Third argument: ‘It is a principle generally accepted in philosophy that every being in Nature is individual, and that it is utterly absurd to suppose (for instance) a really existent triangle that has no precise proportion of sides and angles. If this is absurd in fact and reality, therefore, it must also be absurd in idea, since nothing of which we can form a clear and distinct idea is absurd and impossible.’

I accept that it is impossible that a really existing triangle should have no precise proportion of sides and angles; and impossible that any being should exist that isn’t an individual being (because I think ‘a being’ and ‘an individual being’ mean the same thing). But I do not accept that there can’t be attributes that are common to many individuals. Thus, many figures that really exist may have in common that they are triangles; and many bodies that exist may have in common that they are fluid. Triangle and fluid are not beings—they are attributes of beings.

As to the principle Hume relies on here, that nothing of which we can form a clear and distinct idea is absurd or impossible, I refer you to what I said about that in Essay 4, chapter 3. It is evident that in every mathematical demonstration ad absurdum—and almost half of mathematics is of this sort—we have to •suppose and consequently to •conceive a proposition P that is impossible. We infer consequences from P until we come to a conclusion that is not only impossible but absurd. From this we infer that P is impossible, and therefore that its contradictory is true. . . . This shows that we can clearly and distinctly conceive things that are impossible.

The rest of Hume’s discussion of this subject is devoted to explaining how an individual idea attached to a general term can serve all the purposes in reasoning that have been ascribed to abstract general ideas:

When we have found a resemblance among a number of objects that we often encounter, we apply a single name to all of them, whatever differences we may observe in the degrees of their quantity and quality, and whatever other differences may appear among them. After we have become accustomed to using the word in that way, the hearing of it revives ·in our mind· the idea of one of these objects, and makes the imagination conceive it in all its particular detail.

But along with this idea there is a readiness to survey any of the other individuals to which the name belongs, and to check that no conclusion is being reached that is contrary to any of them. If any such conclusion is reached, the individual ideas that contradict it immediately ‘crowd in on us’ and make us perceive the falsehood of the proposition. If the mind sometimes fails to suggest these ideas, that is because of ‘some imperfection in its faculties’, one that is often the source of false reasoning and sophistry.

This is the substance of Hume’s explanation for what he calls ‘the foregoing paradox, that some ideas are particular in their nature but general in their representation’. I shall make ·three· remarks about this account.

(a) Hume allows that we find a resemblance among several objects—a resemblance that leads us to apply the same name to all of them. If we do this, we have general conceptions. There can’t be a resemblance among objects that have no common attribute; and if there are attributes belonging in common to several objects, and we are able to observe and conceive these attributes and give names to them, that means that we have general conceptions.

I believe indeed we can have a fuzzy perception of a resemblance between two things without knowing what their resemblance consists in. For example, I may see a resemblance between two faces without being able to say precisely in what feature they are alike. But by analysing the two faces, and comparing feature with feature, I may ·eventually· achieve a clear notion of what they have in common. A painter, being accustomed to this kind of analysis, would have formed a clear notion of this resemblance at first sight; to another man it may require some attention.

So there is a •fuzzy notion of resemblance when we make over-all comparisons between objects, and I think that brute animals may have this. There is also a •clear notion of resemblance when we analyse the objects into their different attributes, and perceive them to be alike in some and unalike in others. It is only in this latter case that we give a name to the attributes that the things share. . . . Thus, when I compare cubes made of different materials I perceive them to have in common the attribute of being bounded by six equal squares; and this attribute is all that is signified by applying the name ‘cube’ to them all. When I compare clean linen with snow, I see that they are alike in colour; and when I apply the name ‘white’ to both, this name signifies neither •snow nor •clean linen but •the attribute that they both have.

(b) Hume says that when we have found a resemblance among several objects we apply the same name to all of them.

I should point out that he seems to mix up •proper names and •common names, though they are in fact very different in nature and in the power they have in language. The former are the names of individuals. Two individuals that are alike won’t be given the same proper name on that account, because the whole purpose of a proper name is to distinguish one individual from all others; which is why it’s a grammatical rule that proper names have no plural form. A proper name signifies nothing but the individual whose name it is; and when we apply it to the individual we aren’t affirming or denying anything about him.

A common name is not the name of any individual, but a general term signifying something that is or could be common to many individuals. So common names signify common attributes. Thus, when I apply the name ‘son’ or ‘brother’ to several people, this signifies and affirms that this attribute is common to them all.

This makes it obvious that •applying the same name to several individuals on account of their resemblance can only mean •expressing by a general term something that is common to those individuals and can therefore be truly affirmed of them all. Consistency with grammar and with common sense requires that that’s what it means.

(c) Hume says: ‘It is certain that whenever we use any general term we form the idea of individuals. The word raises up an individual idea, and makes the imagination conceive it with all its particular details.’ He takes a lot of trouble to explain this fact as an effect of custom.

But before working to explain the fact, we should establish that it is a fact. I can see no reason to believe it; I think a farmer can talk of his sheep and his black cattle without conceiving in his imagination one individual with all its particular details. If I am right about this, the whole of Hume’s theory of general ideas falls to the ground. . . .

Hume observes that ‘the idea of an equilateral triangle of an inch perpendicular may serve us in talking of a figure, a rectilinear figure, a regular figure, a triangle, and an equilateral triangle’. I say that the man who uses these general terms either understands their meaning or he doesn’t. If he doesn’t understand their meaning, all his talk about them will be mere sound without sense, and the particular idea Hume mentions can’t enable him to speak of them with understanding. If he does understands the meaning of the general terms, he’ll have no use for the particular idea. . . .

Essay 6: Judgment

Chapter 1: Judgment in general

Chapter 2: Common sense

Chapter 3: The views about judgment of Locke and other philosophers

Chapter 4: First principles in general

Chapter 5: The first principles of contingent truths

Chapter 6: The first principles of necessary truths

Chapter 7: Ancient and modern opinions about first principles

Chapter 8: Prejudices, the cause of error

Chapter 1: Judgment in general

Judging is an operation of the mind that is so familiar to everyone who has understanding, and its name is so common and so well understood, that it doesn’t need to be defined.

Just as one can’t by a definition give a notion of colour to a man who never saw colours, so you can’t by any definition to give a clear notion of judgment to a man who •hasn’t judged often and •isn’t capable of reflecting attentively on this act of his mind. The best use of a definition is to prompt him to that reflection; and without reflection the best definition will be apt to mislead him.

The definition commonly given of judgment by the more ancient writers in logic was that judgment is an act of the mind by which one thing is affirmed or denied of another. This is as good a definition of it as can be given, I think. Further on in this Essay you’ll see why I prefer it to some later definitions. Without purporting to give any other definition, I shall make two ·critical· remarks on this one, and then offer some general remarks about judgment.

(1) It is true that we express our judgments by affirming or denying, but there can be judgments that are not expressed. Judgment is a solitary act of the mind, and the expression of it by affirmation or denial is not at all essential to it. It can be silent and not expressed. Indeed, we all know that men may judge contrary to what they affirm or deny; so the definition must be understood to be talking of mental affirmation or denial—which is merely another name for judgment.

(2) Affirmation and denial is very often the expression of testimony, which is a different act of the mind from judgment and ought to be distinguished from it.

A judge asks a witness what he knows about some event to which he was an eye-witness. He answers by affirming or denying something. But his answer doesn’t express his judgment; it is his testimony. On the other hand, I ask a man his opinion on some matter of science or literary criticism. His answer isn’t testimony; it’s the expression of his judgment.

Testimony is a social act, and it is essential to it to be expressed by words or signs. ‘Silent testimony’ is a contradiction; but there is no contradiction in ‘silent judgment’—a judgment can be complete without being expressed.

In testimony a man swears his truthfulness for what he affirms, so that false testimony is a lie. But a wrong judgment is not a lie; it is only an error.

In all languages, I think, testimony and judgment are expressed by the same form of speech: an affirmative or negative proposition, with a verb in the so-called ‘indicative mood’. To distinguish them by the form of speech we would need two indicative moods for verbs—one for testimony and another to express judgment. I don’t know of any language where this is found. Why? It can’t be that the vulgar cannot distinguish the two, for everyone knows the difference between a lie and an error of judgment. The real reason is that the •content of what someone says and the •context in which he says it make it easy for us to tell whether he intends to give his testimony or merely to express his judgment.

Although men must have judged many times before lawcourts were established, it is very probable that there were courts before anyone started to theorize about judgment; so the word ‘judgment’ may have been borrowed from the practice of courts. Just as •a judge, after taking the proper evidence, passes sentence in a case—a sentence that we call his ‘judgment’—so •the mind, with regard to whatever is true or false, passes sentence or decides according to the evidence that appears. Some kinds of evidence leave no room for doubt: sentence is passed immediately, without looking for or hearing any contrary evidence, because the thing is certain and widely known. In other cases it is appropriate to weigh evidence on both sides before passing sentence. The analogy between a law-court and this inner court of the mind is too obvious to be overlooked by anyone who ever appeared before a judge. And it is probable that the word ‘judgment’, as well as many other words we use in speaking of this mental operation, are based on this analogy.

Having offered these preliminaries, so that you will clearly understand what I mean by ‘judgment’, I proceed to make some general observations concerning judgment. ·There will be four of them, with the fourth occupying about two-thirds of the chapter·.

(1) Judgment is an act of the mind that is of a radically different kind from simple apprehension or the bare conception of a thing. [For ‘simple apprehension’ see Essay 1, chapter 7.] There would be no need to say this if it weren’t that some philosophers have been led by their theories to a contrary opinion.

Although there can’t be any judgment without a conception of the things about which we judge, ·the converse doesn’t hold·—there can be conception without any judgment. Judgment can only be expressed by a proposition, and a proposition is a complete sentence; but simple apprehension can be expressed by a word, or by words, that don’t make a complete sentence. There can be simple apprehension of a proposition, but everyone knows that it’s one thing to •apprehend a proposition—i.e. to conceive what it means—and quite another thing to •judge it to be true or false.

It is self-evident that every judgment must be either true or false; but simple apprehension or conception can’t be either be true or false, as I showed in Essay 1, chapter 7.

One judgment can contradict another; and it is impossible for a man to have at the same time two •judgments that he perceives to be contradictory. But contradictory propositions may be •conceived at the same time without any difficulty. That the sun is bigger than the earth and that the sun is not bigger than the earth are contradictory propositions. Anyone who apprehends the meaning of •either of them apprehends the meaning of •both. But he can’t possibly judge both to be true at the same time. He knows that if either is true the other must be false. For these reasons I hold it to be certain that judgment and simple apprehension are radically different acts of the mind.

(2) There are •notions or •ideas whose source is the faculty of judgment. If we didn’t have that faculty, those notions or ideas couldn’t have entered into our minds; and to people who do have that faculty, and are capable of reflecting on its operations, •they are obvious and familiar. They include the notions of

judgment

proposition

subject, predicate, and copula of a proposition

affirmation and negation

true and false

knowledge

belief and disbelief

opinion

assent

evidentness.

We couldn’t get these notions from any source other than reflecting on our judgments. ·And the list could be lengthened enormously, because· very many of our notions or ideas concern relations of things, and I shall show later—·near the end of this chapter·—that we can’t have an idea of any relation without some exercise of judgment.

(3) In people who are old enough to have understanding, judgment necessarily accompanies all •sensation, •sense-perception, •consciousness, and •memory; but not •conception.

I restrict this to people who are old enough to have understanding, because there may be a question as to whether very young infants have any judgment or belief at all. The same question arises regarding brute animals and some mentally retarded people. This question is irrelevant to my present topic, and I say nothing here about it, but merely confine myself to people who do have the use of judgment.

[The word ‘determination’, which is about to become prominent, connects with settling, deciding, concluding, intellectually opting, or the like. No current word could safely be put in its place; you’ll have to get the idea from the context.]

It is obvious that someone who •feels pain judges and believes that he is really in pain. The man who •perceives an object believes that it exists and is what he clearly perceives it to be; and it’s not in his power to avoid such a judgment. The same holds for •memory and for •consciousness. I shan’t argue about whether judgment should be called a necessary accompaniment of •these operations or rather a part or ingredient of them; but it’s certain that all of them are accompanied by a determination that something is true or false, and a consequent belief. If this determination isn’t judgment then we have no name for it; it isn’t simple apprehension, nor is it reasoning; it

•is a mental affirmation or negation,

•may be expressed by an affirmative or negative proposition, and

•is accompanied by the firmest belief.

These are the characteristics of judgment; and I have to call it ‘judgment’ until I can find another name for it.

The judgments we form are either of necessary things or of contingent things. That three times three is nine, that the whole is greater than a part, are judgments about necessary things. Our assent to such necessary propositions isn’t based on any operation of sense, of memory, or of consciousness, and it doesn’t require the agreement of any of those. The only other operation that goes along with it is conception, which must accompany all judgment; so we can call this judgment of necessary things ‘pure judgment’. ·In contrast with this·, our judgment of contingent things must always rest on some other operation of the mind, such as sense or memory or consciousness—or belief in testimony, which is itself based on sense—·and is in that way not pure·. That I now write on a table covered with green cloth is a contingent proposition which I judge to be most undoubtedly true. My judgment is based on my •perception, and is a necessary accompaniment or ingredient of my perception. That I dined with Dr Stewart yesterday I judge to be true because I •remember it, and my judgment necessarily goes along with this remembering or is a part of it.

Ordinary language contains many forms of speech showing that the senses, memory, and consciousness are regarded as judging faculties. We say that a man ‘judges colours’ by his eye, ‘judges sounds’ by his ear. We speak of ‘the evidence of the senses’, ‘the evidence of memory’, ‘the evidence of consciousness’. Evidence is the basis for judgment, and when we see evidence it is impossible for us not to judge.

When we speak of seeing or remembering anything, we hardly ever add that we judge it to be true; but the reason for that seems to be that such an addition would be superfluous because everyone knows that what I see or remember I must judge to be true. This is like the reason why, when speaking of something that is self-evident or strictly demonstrated, we don’t say that we judge it to be true. This would be superfluous because everyone knows that we must judge something to be true if we think it is self-evident or has been demonstrated.

[Reid gives more examples where the addition of ‘. . . and I judge it to be true’ would be true but superfluous. He winds up this discussion thus:] A pregnant woman never says that when she went on a certain journey she carried her child along with her. We know that while the child is in her womb she must carry it along with her. Well, some mental operations can be said to carry judgment in their womb, and can no more leave it behind them than the pregnant woman can leave her child. That’s why in speaking of such operations we don’t explicitly mention judgment.

Perhaps this fact about our speech led some philosophers into the opinion that in sense-perception, memory, and consciousness there is no judgment at all. Because it isn’t mentioned in speaking of these faculties, they have inferred that judgment doesn’t accompany them—that they are only different kinds of simple apprehension or idea-acquisition, and that judging is no part of their job.

[Reid criticises Locke’s view that knowledge is one thing and judgment another, quoting passages from the Essay that express this view. All Locke’s examples of ‘knowledge’, he says, also deserve the name ‘judgment’. Then:] So as to avoid disputes about the meanings of words, please understand that I give the name ‘judgment’ to every determination of the mind concerning what is true or what is false. . . .

·Here is a different possible explanation for why philosophers have wrongly restricted the domain of judgment·. Judgments based on the evidence of the senses, of memory, and of consciousness put all men on a level. So far as these are concerned, the philosopher has no privilege above the illiterate person or even above the savage. Their reliance on the testimony of these faculties is as firm and as well grounded as his. Where he is superior to them is in judgments of another kind—judgments about things that are abstract and necessary—and he is reluctant to give the name ‘judgment’ to something in respect of which the most ignorant and primitive of our species are his equals.

But philosophers have never been able to give any definition of ‘judgment’ that •doesn’t apply to the determinations of our senses, our memory, and consciousness; or any definition of ‘simple apprehension’ that •can include those determinations.

Our judgments of this kind are purely the gift of Nature, and there is nothing we can do to improve them. One man’s memory may hold more than another’s, but both men rely with equal confidence on what they clearly remember. One man’s sight may be more acute, or his feeling more delicate, than another’s, but the men are on a par in trusting the clear testimony of their sight and touch.

And just as we have this belief because of how we are built, without any effort of our own, so no effort of ours can overturn it.

The sceptic may persuade himself of the •general thesis that he has no reason to believe his senses or his memory, but in •particular cases that concern him his disbelief vanishes and he finds himself having to believe both his senses and his memory.

These judgments can in the strictest sense be called ‘judgments of Nature’. Nature has laid them on us, whether we want them or not. They aren’t acquired by any use of our faculties and can’t be lost by any misuse of them. It is clearly necessary for our survival that this should be so. For if belief in our senses and in our memory had to be learned by education, the race of men would die out before they learned this lesson. . . .

I admit that our entitlement to count as reasonable beings depends on our making the •‘judgments of Nature’ that I have been discussing and building other judgments on the basis of them. But the •former oughtn’t to be despised, for they are the foundation on which the grand superstructure of human knowledge must be constructed. In superstructures the foundation is usually overlooked, and so it has been here. The more lofty achievements of the human mind have attracted the attention of philosophers, while they have barely glanced at the humble foundation on which the whole structure rests.

(4) Judgment has to be exercised in •the formation of all abstract and general conceptions, however simple or complex, in •dividing ·things into classes·, in •defining, and in general in •forming all clear and distinct conceptions of things—the only conceptions that are fit materials for reasoning. These operations are tied to each other, which is why I bring them all into my observation (4). They are more closely tied to our rational nature than those mentioned in (3), which is why I am taking them separately.

Don’t misunderstand me. I am not denying that abstract notions and other precise notions of things, once they have been formed, can be barely conceived without any exercise of judgment about them. I have no doubt that they can. What I am saying is that some judgment must be exercised in the first formation of such notions in the mind. ·Here is why·.

To distinguish the different attributes belonging to a single thing, you have to judge •that they are really different and distinguishable, and •that they relate to the thing in the way that logicians express by saying that they ‘can be predicated’ of it. And we can’t generalise without judging that a given attribute does or can belong to many individuals. I have shown that our simplest general notions are formed by these two operations, distinguishing and generalising. So judgment is exercised in forming the simplest general notions.

Then there are more complex notions, which I have shown to be formed by combining the simpler ones. Such combinations are not made at random, but for a purpose: we form complex general notions to make it easier for us to arrange our thoughts in discourse and reasoning; so we select, out of countless possible combinations, only the ones that are useful and necessary; and judgment is needed to make those selections.

It seems clear that judgment must be used in dividing [= ‘classifying’] as well as in distinguishing. It is one thing to divide a subject properly, another to cut it in pieces. . . . Reason has discovered rules of division that have been known to logicians for more than two thousand years. For definition, also, there are rules of no less antiquity and authority. ·And the application of rules requires judgment·. No doubt a man can divide or define properly without •attending to the rules, even without •knowing them. But this can only be when he can judge to be right in a particular case something that the rule says is right in all cases.

So my general thesis is this: without some degree of judgment we can’t form precise and clear notions of things, so that one of judgment’s tasks is to help us in forming clear and distinct conceptions of things, the only conceptions that are fit for use in reasoning.

To philosophers who have always •regarded the formation of ideas of every kind as falling into the category of simple apprehension, and have •thought that judgment’s only role is to put ideas together in affirmative or negative propositions, my view will probably seem paradoxical. So I ought to provide some confirmation for it.

[Reid says that he already has provided confirmation, in his points about distinguishing, dividing and defining. Then:]

There can’t be any proposition in ·any· language that doesn’t involve some general conception. The proposition that I exist, which Descartes thought to be the first of all truths and the basis for all knowledge, can’t be conceived without the conception of existence, which is one of the most abstract general conceptions. A man can’t believe in his own existence, or the existence of anything he sees or remembers, until he has enough judgment to distinguish things that really exist from things that are only conceived. He sees a woman six feet tall, and judges that she exists, because he sees her; he conceives a woman sixty feet tall, and doesn’t judge that she exists, because he only conceives her. Well, then, can he attribute existence to the first woman and not to the second without knowing what existence means? Not possibly! [Reid’s example concerned tall men, not women; the change is made in the interests of clarity.]

I can’t discover how early the notion of existence enters the mind, but it must certainly be in the mind as soon as we can affirm of anything—understanding what we are saying—that it exists.

In every other proposition, the predicate at least must be a general notion—because a predicable is the same thing as a universal. In addition, every proposition either affirms or denies. And no-one can have a distinct conception of a proposition unless he clearly understands what it is to affirm or deny. But these are very general conceptions and, I repeat, their source and origin is judgment.

·THE INFINITE REGRESS OBJECTION·

I am aware that a strong objection may be made to this reasoning, and that it may seem to lead to an absurdity or a contradiction ·or an infinite regress·. It goes like this:

Every judgment is a mental affirmation or negation. I have said that some previous exercise of judgment must have occurred, if one is to understand what is meant by affirmation or negation. It follows that every exercise of judgment must be preceded by an exercise of judgment—which is absurd.

Here is a variant on that:

Every judgment can be expressed by a proposition, and •a proposition must be conceived before we can judge concerning it. I have said that •we can’t conceive the meaning of a proposition without a previous exercise of judgment. It follows that •any judgment must be preceded by the conception of a proposition, and that •the conception of any proposition must be preceded by judgment—which is a contradiction.

Please notice that I have limited what I have said to clear conception and some degree of judgment; and I look to those qualifications to keep me out of this labyrinth of absurdity and contradiction. The faculties of conception and judgment are like us—they start as infants, and grow to maturity. What I have been saying is limited to their mature state. I believe in their infant state they are very weak and unclear, and that very gradually they grow to maturity, helping one another along the way. Which of them first began this friendly relationship? I am quite unable to answer that. It’s like the question about the bird and the egg.

In the present state of things it is true that every bird comes from an egg and every egg from a bird; and each may be said to precede the other. But if we go back to the origin of things, there must have been a bird that didn’t come from any egg, or an egg that didn’t come from any bird.

Similarly, in the mature state of man the clear conception of a proposition presupposes some earlier use of judgment, and clear judgment presupposes clear conception. Each can truly be said to precede the other, as the bird precedes the egg and the egg precedes the bird. But if we run this series back to its origin—i.e. to the first proposition that was ever conceived by the ·first· man and the first judgment he ever formed—I have nothing to say about those; I don’t know how or in what order they were produced, any more than I know how bones grow in the womb of a pregnant woman. The first exercise of the faculties of conception and judgment is hidden from us.

Consider the analogous case of an artist—a carpenter, say—who can’t work at his art without tools, which must be made by art. So the art must be exercised to make the tools, and the tools are necessary for the exercise of the art. This presents the same appearance of contradiction as does my thesis that some degree of judgment is needed in order to form clear and distinct conceptions of things. Such conceptions are the tools we must use in judging and in reasoning, and without them we’ll do very bungling work; yet these tools can’t be made without some exercise of judgment.

·BACK TO THE MAIN THREAD·

The need for some degree of judgment in forming precise and clear notions of things will show up again if we consider carefully what notions we can form, without any help from judgment, of (a) the objects of the senses, (b) the operations of our own minds, and (c) the relations amongst things.

(a) Everyone agrees that our first notions of sensible objects are acquired through the external senses alone, probably before judgment makes an appearance; but these first notions are not simple, nor are they precise and clear. They are crude and unclear, and like ‘a rough unordered mass of things’ [Reid quotes this from Ovid, in Latin]. Before we can have any clear notion of this mass we must analyse it; we have to separate in our thought the different kinds of parts it contains; the simple elements that were previously hidden in the common mass have to be sorted out separately and then re-assembled into one whole.

That is how we form clear notions even of the objects of sense; but we are apt to overlook this process of analysis and re-assembly, because it becomes habitual to us, and then we can do it so smoothly and easily that we don’t notice it and attribute the clear notion we have formed of the object to the senses alone, ·with no input from judgment·. We are all the more likely to do this because our senses give testimony regarding each of an object’s sensible qualities—once we have distinguished them from one another.

You perceive, for instance, an object that is white, round, and a foot in diameter. I agree that it is by sense—·by your eyesight·—that you perceive all these attributes of the object. But if you hadn’t been able to distinguish the colour from the shape, and both from the size, your eyesight would have given you only one complex and confused notion of all these attributes jumbled together.

A man who can say with understanding, or can determine in his own mind, that this object is white must have distinguished whiteness from other attributes. If he hasn’t made this distinction, he doesn’t understand what he is saying.

Suppose we show a cube of brass to a one-year-old child and to a man. The regularity of the shape will attract the attention of both. The two have equally good senses of sight and touch, so if the man finds in this cube something that the child can’t find in it, that must be due not to the senses but to some other faculty that ·the man has and· the child has not yet attained. The man •can easily distinguish the body from the surface that terminates it, •can perceive that this surface is made up of six planes of the same shape and size, and •can perceive that each of these planes has four equal sides and four equal angles, and that the opposite sides of each plane are parallel, as are also the opposite planes. The child cannot discover any of this.

You’ll surely agree that a man of ordinary judgment •can observe all this in a cube that he attends to and thinks about carefully, and •can give the name ‘square’ to a plane terminated by four equal sides and four equal angles, and the name ‘cube’ to a solid terminated by six equal squares. All this is nothing but analysing into its simplest elements the shape of the object presented to his senses, and then re-assembling those elements to get the object back.

By this analysis and re-assembly two effects are produced. (i) From the one complex object which the man’s senses presented, though it is one of the simplest the senses can present, he extracts many simple and clear notions of

straight lines

angles

plane surface

solid

equality

parallelism

—notions that the child isn’t yet able to acquire. (ii) When he considers the cube as made up of these elements put together in a certain order, he has—then and not before—a clear and scientific notion of a cube. The child doesn’t conceive those elements, let alone conceive in what order they must be assembled in order to make a cube; so he has no precise notion of a cube that would enable him to reason about it.

I think we can infer from this that the notion we have from the senses alone, even of the simplest objects of the senses, is unclear and incapable of being either described or used in reasoning until it is analysed into its simple elements and regarded as built up out of them. . . .

A clear notion of an object, even of an object of the senses, is never acquired in an instant; but the senses do their job in an instant. Time is required not •to see the thing better but •to analyse it—to distinguish its different parts and their relation to one another and to the whole.

[Reid goes on to say that when we are in a state of high emotion our sense-perceptions are worse because our judgment is worse. At these times, ‘the eye of sense is open but that of judgment is shut’. Then:]

So there are notions of the objects of sense that are crude and unclear, and there are others that are distinct and scientific. The former can be acquired from the senses alone, but the latter can’t be obtained without some degree of judgment. The clear and precise notions that geometry gives us of

point

straight line

angle

square

circle

ratios, direct and inverse,

and others of that kind, can’t get into any mind that doesn’t have some degree of judgment. They are not strictly ideas of the senses, nor are they acquired by combining ideas of the senses. We get them, rather, by •analysing into their simplest elements the ideas or notions we get through the senses, and •re-combining these elements into various precise and elegant forms that the senses never did and never can exhibit.

If Hume had attended properly to this, it ought to have headed off his very bold attempt—fourteen pages of it!—to prove that geometry is based on •ideas that are not exact and •axioms that are not precisely true (Treatise I.ii.4). A mathematician might be tempted to think that someone who seriously argues this doesn’t know much about geometry; but I think its cause lies elsewhere—in Hume’s zeal for his own system. We see that even men of genius can be drawn into strange paradoxes by their attachment to a favourite idol of the understanding, when it demands such a costly sacrifice.

We protestants think that Roman catholics pay a very large tribute to their church’s authority, when in obedience to its decrees they renounce their five senses. But Hume ·pays an even larger tribute: his· devotion to his system leads him even to trample on mathematical demonstration.

The basic doctrines of his system are that •all the perceptions of the human mind are either impressions or ideas, and that •ideas are only faint copies of impressions. The idea of a straight line, therefore, is only a faint copy of some line that has been seen or felt by touch; and the faint copy can’t be more perfect than the original. Now, obviously the axioms of geometry aren’t exactly true of lines like that, for two lines that are straight to our sight or touch can intersect twice. If therefore we can’t form any notion of straight line more precise than what we have from the senses of sight and touch, geometry has no solid foundation. ·But we can run the argument the other way·. If the geometrical axioms are precisely true, the idea of straight line is not copied from any impression of sight or touch, and must have a different origin and a more perfect standard.

Just as the geometrician by reflecting on the •extension and shape of matter forms a set of notions more precise and scientific than any that the senses exhibit, so also the natural philosopher by reflecting on •other attributes of matter forms another set of notions, including density quantity of matter velocity

density

quantity of matter

velocity

momentum

fluidity

elasticity

centres of gravity and of oscillation.

These notions are precise and scientific; but they can’t get into a mind that doesn’t have some degree of judgment, and we can’t make them intelligible to children until they have some maturity of understanding. . . . And the same is true for the terminology of every science and every art about which we can reason. Children have their five senses as perfect as men do for years before they are capable of distinguishing, comparing, and perceiving the relations of things so as to be able to form such notions. They acquire the intellectual powers by a slow and gradual progress, and by means of them they learn to form clear and precise notions of things—notions that the senses could never have imparted.

(b) So much for the notions of the objects of sense that we get from the senses alone, ·unaided by judgments·. Now let us consider what notions of the operations of our minds we can have from consciousness alone, ·unaided by judgments·.

Locke very properly calls consciousness an ‘internal sense’ (Essay II.i.4). It gives the same kind of immediate knowledge of things in the mind—i.e. of our own thoughts and feelings—that the senses give us of external things. There is this difference, however, that an external object may be static, so that the senses can be brought to bear on it for some time. But the objects of consciousness are never still; the stream of thought flows like a river, never stopping for a moment; the whole train of thought passes successively under the eye of consciousness, which is always employed about the present. But is it consciousness that analyses complex operations, distinguishes their ingredients, and sorts them into distinct lots under general names? Surely not! This work can’t be done without reflection, recollecting and judging concerning what we •were conscious of and •now remember. This reflection doesn’t appear in children. Of all the powers of the mind it seems to one of the last to show up, while consciousness is among the earliest.

Because consciousness is a kind of internal sense, it can’t give us clear and precise notions of the operations of our minds, any more than the external senses can give such notions of external objects. •Reflection on the operations of our minds is the same kind of operation as •that by which we form clear notions of external objects. The two differ not in their nature but only in that one engages with external objects and the other with internal ones. Each could quite properly be called ‘reflection’.

Locke has restricted the word ‘reflection’ to the kind of reflection that is concerned with the operations of our minds. I don’t think that custom, which is the arbiter of language, entitles him to this usage. Surely I can reflect on what I have •seen or •heard as well as on what I have •thought. . . . Locke has also confused •reflection with •consciousness, and seems not to have realized that they are different powers and appear at very different periods of life.

If that eminent philosopher had been aware of these mistakes about the meaning of the word ‘reflection’, I think he would have seen that just as

•we can form clear and precise notions of the operations of our minds only by reflection, ·properly socalled·, and not by consciousness without reflection,

so also

•we can form clear notions of the objects of the senses only by reflection, and not by the senses without reflection.

Reflection on anything, whether external or internal, makes it an object of our intellectual powers, by which we survey it on all sides and make such judgments about it as appear to be sound and true.

(c) I proposed in the third place to consider our notions of the relations of things. What I have to say about this is that in my opinion: without judgment, we can’t have any notion of relations.

[In the rest of this chapter, and early in the next, Reid will use ‘compare’ in a sense that was current in his day: to ‘compare’ two things, in this sense, is just to hold them before your mind at the same time in order to see how they are inter-related, not just to see how (un)alike they are. We still use ‘compare’ in that broader sense, when we speak of ‘getting together to compare notes’.]

There are two ways in which we get the notion of relations. The first is by comparing the related objects, after we have first had the conception of each. By this comparison we perceive the relation, perceiving it either immediately or through a process of reasoning. I perceive immediately that my foot is longer than my finger, and that three is half of six. This immediate perception is immediate and intuitive judgment. That the angles at the base of an isosceles triangle are equal I perceive by a process of •reasoning, and everyone will agree that there is judgment in •that.

The other way for us to get the notion of relations—a way that seems not to have occurred to Locke—is by attending to one of the related objects and perceiving or judging that its nature is such that it must have a certain relation to something else—perhaps something we have never thought of before. In this way, our attention to one of the related objects produces the notion of a related object and of a certain relation between them.

Thus, when I attend to colour, shape, weight, I can’t help judging these to be qualities that can’t exist except in a subject—i.e. in something that is coloured, shaped, heavy. If I hadn’t perceived them to be qualities, I would never have had any notion of the thing that has them or of their relation to it.

By attending to the operations of thinking, memory, and reasoning, we perceive or judge that there must be something that thinks, remembers, and reasons—something that we call ‘the mind’. When we attend to any change that happens in Nature, judgment informs us that this change must have had a cause that had the power to produce it; and thus we get the notions of cause and effect and of the relation between them. When we attend to body, we perceive that it can’t exist without space; and so we get the notion of •space (which is not an object of sense or of consciousness) and of •the relation that each body has to its place, which is a certain portion of unlimited space.

So I think that all our notions of relations can be more properly be ascribed to judgment as their source than to any other power of the mind. ‘·Can’t I conceive of a relation without making any judgment concerning it?’ Yes, but·

before conceiving relations without judging about them, we must first perceive them by our judgment.

That is analogous to this: ‘·Can’t I conceive of a colour without seeing it?’ Yes, but·

before we can conceive colours without seeing them, we must first perceive colours by sight.

When Locke comes to speak of the ideas of relations, I don’t think he says that they are ideas of sensation or reflection, but only that they ‘terminate in’ and ‘are concerned about’ ideas of sensation or reflection.

The notions of unity and number are so abstract that they couldn’t possibly get into a mind that doesn’t yet have any degree of judgment. We see how hard it is for children to learn to use and understand the names even of small numbers, how slow they are at this, and how triumphant they are when they succeed. Every number is conceived by its relation to unity or to known combinations of units; and for that reason, as well as because of its abstract nature, all clear notions of number require some degree of judgment. . . .

Chapter 2: Common sense

The word ‘sense’ seems to have a different meaning in common language from its meaning in the writings of philosophers; and those different meanings are apt to be muddled together, giving rise to embarrassment and error.

I shan’t go back to ancient philosophy on this matter. Modern philosophers regard •sense as a power that has nothing to do with •judgment. They regard •sense as the power by which we receive certain ideas or impressions from objects, and •judgment as the power by which we compare those ideas and perceive their necessary agreements and disagreements.

The external senses give us the ideas of colour, shape, sound, and other qualities—primary or secondary—of bodies. Locke called consciousness an ‘internal sense’ because through it we have the ideas of thought, memory, reasoning, and other operations of our own minds. Hutcheson thought that we have simple and original ideas that can’t be attributed either to the external senses or to consciousness, so he introduced other internal senses such as the sense of harmony, the sense of beauty, and the moral sense. Ancient philosophers also spoke of ‘internal senses’, of which memory was thought to be one.

But all these ‘senses’, whether external or internal, have been represented by philosophers as the providers to our minds of •ideas, without including any kind of •judgment. Hutcheson defines a sense as the mind’s determination to receive ideas from the presence of an object independently of our will. And Priestley writes:

Philosophers have used the word ‘sense’ to name the faculties in consequence of which we are liable to feelings relative to ourselves only, and from which they haven’t claimed to draw any conclusions concerning the nature of things; whereas truth is not •relative but •absolute and real.

Not so! In common language ‘sense’ always implies judgment. A man of sense is a man of judgment. Good sense is good judgment. Nonsense is what is obviously contrary to right judgment. Common sense is the degree of judgment that is common to men with whom we can converse and transact business.

Philosophers call seeing and hearing ‘senses’ because we have ideas by them; the vulgar call them ‘senses’ because we judge by them. We judge colours by the eye, sounds by the ear, beauty and ugliness by taste, right and wrong in conduct by our moral sense or conscience.

Philosophers who portray sense as having only one role, namely to provide us with ideas, slip without realizing it into the popular opinion that the sense are judging faculties. Thus Locke, writing about the thesis that the quality of colour really exists and has a being outside me: ‘The best assurance I can have, the best my faculties are capable of, is the testimony of my eyes; they are the proper and sole judges of this thing’ (Essay IV.xi.2). This popular meaning of the word ‘sense’ is not peculiar to the English language. The corresponding words in Greek, Latin, and (I believe) all the European languages have the same meaning-spread. The Latin words sentire, sententia, sensa, sensus—from the last of which the English word ‘sense’ is borrowed—stand for judgment or opinion, and are applied equally to objects of external sense, of taste, of morals, and of the understanding.

I can’t claim to explain why a word that is not a technicality, and is familiar in common conversation, should have such a different meaning in philosophical writings. I merely remark that the philosophical meaning corresponds perfectly with the account that Locke and other modern philosophers give of judgment. For if the •only role of the external and internal senses is to provide the mind with the ideas about which we judge and reason, it seems to be a natural consequence that •the only role of judgment is to compare those ideas and to perceive their necessary relations.

These two opinions seem to be so connected that one may have been the cause of the other. Anyway, I think that if both are true there is no room left for any knowledge or judgment either about the real existence of contingent things or about their contingent relations.

To return to the popular meaning of the word ‘sense’: it would be much harder to find good authors who never use the word with that meaning than to find ones who do. [Reid then quotes eight lines by Pope, in which ‘good sense’ is described as ‘the gift of Heaven’ and ‘a light which in yourself you must perceive’. Then:] This inner light or sense is given by heaven to different persons in different degrees. We must have a certain degree of if we are to be subjects of law and government, capable of managing our own affairs, and responsible for our conduct towards others. This is called ‘common sense’, because it is common to all men with whom we can transact business or hold accountable for their conduct.

The laws of all civilised nations distinguish •those who have this gift of heaven from •those who don’t. The •latter may have rights that ought not to be violated, but because they have no understanding of their own to direct their actions, the laws arrange for them to be guided by the understanding of others. ·Their lack of common sense· is easily detected through its effects on their actions, through what they say, and even through their physical appearance. When there is a question as to whether or not a man has this natural gift of common sense, a judge or a jury can usually give a confident answer after a short conversation with him.

The same degree of understanding that makes a man capable of •acting with common prudence in the conduct of life makes him capable of •discovering what is true and what is false in matters that are self-evident and that he is clear about in his mind.

All knowledge and all science must be built on principles that are self-evident; and every man who has common sense is a competent judge of such principles when he conceives them clearly. That is why disputes very often come down to appeals to common sense.

When the disputants agree on the first principles on which their arguments are based, there is room for reasoning; but when one denies something that the other finds too obvious to need or to be capable of proof, reasoning seems to be at an end; an appeal is made to common sense, and each disputant is left to enjoy his own opinion.

There seems to be no cure for this, and no way to discuss such appeals ·to common sense·, unless the decisions of common sense can be encoded in rules that all reasonable men accept. If this were possible it would be very desirable, and would give logic something it needs; and why shouldn’t it be possible for reasonable men to agree on things that are self-evident?

All I want to do in this chapter is to explain the meaning of ‘common sense’, so that it won’t be treated (as some have treated it) as signifying something new or as a phrase without any meaning. I have tried to show that ‘sense’, in its most common and therefore its most proper meaning, signifies judgment (though philosophers often use it with a different meaning). This makes it natural to think that ‘common sense’ should mean common judgment; and so it really does.

It may be hard to settle the precise limits separating common judgment from •what is beyond it, on the one hand, and from •what falls short of it, on the other. Men who agree about the meaning of the phrase ‘common sense’ may disagree about where those limits lie, or may never have even thought of fixing them. There is nothing puzzling about this, any more than there is about the fact that all Englishmen mean the same thing by ‘the county of York’ though not one in a hundred can point out its precise boundaries.

Indeed, it seems to me that ‘common sense’ is as well understood and as free from ambiguity as ‘the county of York’. We find the phrase in countless places in good writers; we hear it on countless occasions in conversation; and as far as I can tell it is always used with the same meaning. That is probably why it is so seldom defined or explained. [Reid then quotes Bentley, as quoted in Johnson’s dictionary: ‘. . . power and abilities which we call natural light and reason and common sense’. Then:] It is true that ‘common sense’ is a popular and not a scholarly phrase; and most philosophers who have written systematically about the powers of the understanding have used it only occasionally, and the same is true of other writers. But I recall two philosophical writers who are exceptions to this remark. One is Buffier, who wrote at length about common sense as a source of knowledge more than fifty years ago.

The other is Berkeley, who I think has laid as much stress on •common sense, in opposition to the •doctrines of philosophers, as any philosopher that has come after him. Look back at the quotations from him in Essay 2, chapter 10; I needn’t repeat them here.

Men rarely ask what common sense is, because everyone thinks that he has it. . . . Yet I remember two very eminent authors who have asked this question; and we should hear their views on this topic that is so often mentioned and so rarely discussed.

It is well known that Lord Shaftesbury called one of his treatises Sensus Communis: an Essay on the freedom of wit and humour, in a letter to a friend. [Sensus communis is Latin for ‘common sense’.] In this, he reminds his friend of a free-wheeling conversation they once had with some of their friends on the subjects of morality and religion. Amidst the different opinions launched and defended with great vivacity and ingenuity, every now and then someone would make an appeal to common sense. Everyone allowed the appeal; no-one questioned the authority of the court; until someone whose intellect they had never questioned solemnly asked them to tell him what common sense is. He said:

If by the word ‘sense’ we were to understand opinion and judgment, and by the word ‘common’ the whole or any considerable part of mankind, it would be hard to discover where there is any common sense; for views agreeing with the ‘sense’ of one part of mankind would conflict with the ‘sense’ of another part. And if ‘common sense’ were to be determined by the majority, it would change as often as men changed.

In religion, he said, common sense was as hard to determine as catholic or orthodox; one sect’s absurdity was another’s demonstration. He continued:

In political matters, if plain British or Dutch ‘sense’ were right, Turkish and French ‘sense’ must certainly be wrong. Passive obedience—·i.e. unquestioning obedience to a ruler with unlimited powers·—seemed ·to us· to be mere nonsense; but it turned out to be the ‘common sense’ of •a considerable proportion of our fellow-countrymen, •a larger proportion in Europe, and perhaps •a majority of all the world. As for morals, the difference is still wider; for even the philosophers can never agree on a single system. And even some of our most admired modern philosophers have openly told us that virtue and vice have no law or criterion except mere fashion and vogue.

That is the substance of the gentleman’s speech. I think it explains the meaning of ‘common sense’ perfectly, and contains ·the whole case·—everything that has been said or can be said—against the authority of common sense and the permissibility of appeals to it.

There is no report of any immediate answer to this speech, which might incline us to think that the noble author agrees with the views of the intelligent gentleman whose speech he quotes. But that would be wrong, as is clear from the title Sensus Communis given to his work, from his frequent use of the phrase ‘common sense’, and from the whole tenor of the book. [Reid backs this up with a discussion of what Shaftesbury was up to in this work, and quoting some passages including this:]

Some moral and philosophical truths are so evident in themselves that it would be easier •to imagine that half mankind had run mad in precisely the same way than •to admit as truth anything that was advanced against such natural knowledge, fundamental reason, and common sense.

[After adding one more quotation from Shaftesbury, again treating ‘common sense’ as a criterion of truth, Reid presents passages from Fénelon, Cicero, Hume, and Priestley—all using the phrase ‘common sense’ (or its French or Latin equivalent) to stand for a source of knowledge, and thus as implying that common sense involves judgment. Then:]

On the basis of this cloud of testimonies (and I could have given hundreds more), I think that whatever criticism is spread over those who have spoken of common sense as a source of knowledge, or who have appealed to it in matters that are self-evident, will fall lightly on any individual when there are so many to share in it!. . . .

From the account I have given of the meaning of the phrase ‘common sense’, it is easy to see how to use it properly and how to tell when it is being misused.

It is absurd to think that common sense could be in any way opposed to reason. It is indeed reason’s first-born, and just as they are commonly joined together in speech and in writing they are inseparable in their nature.

We ascribe to reason two roles, or two degrees—•to judge concerning self-evident things, and •to draw conclusions that are not self-evident from premises that are. The former is the job of common sense—its only job. So the whole of common sense coincides with reason; indeed ‘common sense’ is only another name for one branch (or degree) of reason. ‘Why give it a name of its own, when you admit that it is only a degree of reason?’. . . . There is an obvious reason why this degree of reason should have its own special name. It’s that in the vast majority of mankind no other degree of reason is to be found. It is this degree that entitles them to be called ‘reasonable creatures’. It is this degree of reason—and only this—that makes a man capable of managing his own affairs and accountable for his conduct towards others. So there is the best reason why it should have its own special name.

These two degrees of reason differ in other respects, which would be sufficient to entitle them to distinct names.

The first is purely the •gift of heaven, and where heaven hasn’t given it no education can make up for that. The second is learned by practice and rules when the first is not lacking. A man who has common sense may be taught to reason. But if someone doesn’t have that •gift, no teaching will enable him either to judge concerning first principles or to reason from them.

I have only one other point to make, namely that common sense has more work to do in •refutation than in •confirmation. A conclusion drawn by valid reasoning from true principles can’t possibly contradict any decision of common sense, because truth will always be consistent with itself. And such a conclusion can’t be confirmed by common sense, because it doesn’t lie with common sense’s jurisdiction.

But someone who sets out from false principles, or who makes a mistake in reasoning, may be led to a conclusion that contradicts the decisions of common sense. In this case the conclusion is within the jurisdiction of common sense, even though the reasoning on which it was based is not; and a man of common sense is entitled to reject the conclusion without being able to show the error of the reasoning that led to it. . . .

Chapter 3: The views about judgment of Locke and other philosophers

A difference in what two philosophers mean by a given word ought not to generate disputes between them. But we often need to attend to such differences, so as to prevent verbal disputes. There are indeed no words in ·any· language more liable to ambiguity than the words we use to signify the operations of the mind; and there are sometimes differences of opinion about their precise meaning, even among people who are fair-minded and have good judgment.

I have hinted [here] at what I take to be a peculiarity in Locke concerning the meaning of ‘judgment’, and I mentioned what I think may have led him into it. But I’ll let him speak for himself:

The faculty that God has given to man, to make up for the lack of clear and certain knowledge in cases where that can’t be had, is judgment. Using this, the mind takes its ideas to agree or disagree—that is, takes a proposition to be true or false—without proofs that it perceives as demonstratively self-evident. (Essay IV.xiv.3)

Thus the mind has two faculties having to do with truth and falsehood. •First, knowledge, whereby it certainly perceives and is satisfied beyond doubt of the agreement or disagreement of any ideas. •Secondly, judgment, which is putting together or separating ideas in the mind when their certain agreement or disagreement is not perceived but is presumed to be so. (4)

Knowledge, I think, sometimes signifies •things that are known, sometimes •the act of the mind by which we know them. Similarly, ‘opinion’ sometimes signifies •things that are believed, sometimes •the act of the mind by which we believe them. But judgment is the faculty that is exercised in both these acts of the mind. In knowledge we judge without doubting, in opinion we judge with some mixture of doubt. But Locke is the only writer I know of who has called knowledge a faculty (and even he doesn’t call opinion a faculty!).

Nor do I think that knowledge is confined within the narrow limits that Locke puts around it; because most of what all men call human knowledge concerns things that don’t admit of intuitive or of demonstrative proof.

I have all along used the word ‘judgment’ in a more extended sense than Locke does in the passage quoted above. I use it to stand for the operation of mind by which we determine [= ‘decide’], concerning anything that can be expressed by a proposition, whether it is true or false. Every proposition is either true or false; so is every judgment. A proposition may be simply conceived without judging in regard to it. But when there is not only a conception of the proposition but a mental affirmation or negation, an assent or dissent of the understanding, whether weak or strong, that is judgment.

I think that since the days of Aristotle •logicians have taken ‘judgment’ ·and its equivalents in other languages· in that sense, and so have most •other writers. It does have other meanings, but not ones that are in any danger of being mixed up with this.

[Reid cites a passage by Watts, describing and using ‘judgment’ in the sense that Reid approves of. Then:]

In this meaning, ‘judgment’ extends to every kind of evidentness, whether probable or certain, and to every degree—·every strength·—of assent or dissent. It extends to all •knowledge as well as to all •opinion, the only difference being that in •knowledge it [i.e. the judgment] is more firm and steady, like a house founded on a rock, whereas in •opinion it stands on a weaker foundation, and is more liable to be shaken and overturned.

I don’t go into these differences about the meanings of words in the spirit of ‘Truth is on one side and error on the other’, but ·for two other reasons·. Most of Locke’s terminology is precise and clear, and I wanted to defend my departing from it in this instance. Also, attention to the different meanings that are given to words by different authors is the best way to avoid mistaking verbal differences for real differences of opinion.

The common theory of ideas [see Essay 2, chapter 8 re this phrase] naturally leads to a theory of judgment, which may be a good test of its truth; for as the two are necessarily connected, they must stand or fall together. Here is how Locke describes their connection:

•Since the mind in all its thoughts and reasonings has no immediate object other than its own ideas, which are all it can contemplate, it is evident that our knowledge has to do only with them.

•Knowledge, then, seems to me to be nothing but the perception of the connection and agreement, or disagreement and incompatibility, of any of our ideas. That is all it is. (Essay IV.i.1-2)

The only objection to the validity of this inference is that the proposition from which the inference is made seems to have some ambiguity. For in the first clause of that proposition the mind is said to have ‘no immediate object other than its own ideas’; in the second clause it is said that the mind has no other object at all—that all it can or does contemplate are ideas. If the word ‘immediate’ in the first clause is a mere filler—·conveying the idea that for Locke the only objects are immediate objects·—and isn’t meant to pick out immediate objects of thought as a sub-class of all objects of thought, then the two clauses of that first proposition—

•the mind. . . .has no immediate object other than its own ideas,

•all that a mind can contemplate are its own ideas,

will be perfectly consistent, the second being only a repetition or spelling out of the first; and the inference that our knowledge has to do only with ideas will be perfectly logical.

But if the word ‘immediate’ in the first clause is intended to limit the general proposition, implying that the mind has other objects besides its own ideas though no other immediate objects, then it won’t be true that all it does or can contemplate are ideas, and it won’t validly follow that our knowledge has to do only with ideas.

Well, did Locke mean his antecedent proposition without any limitation by the word ‘immediate’, or did he meant to limit it by that word, thus indicating that some objects— ·though not immediate objects·—of the mind are not ideas? The former alternative seems to me the more probable, for four reasons.

(1) When Locke explicitly defines ‘idea’ in the introduction to the Essay, he says it is ‘whatever is the object of the understanding when a man thinks, or whatever the mind can be engaged with in thinking’. This leaves no room for objects of the mind that are not ideas. The same definition is often repeated throughout the Essay. . . . Now, if it had really been his opinion that some objects of thought are not ideas, this definition, which is the foundation of the whole Essay, would have been very improper and apt to mislead his reader.

(2) Locke has never attempted to show how there can be objects of thought that are not immediate objects; and indeed this seems impossible. For whatever the object is, the man either thinks of it or he doesn’t: there is no third way between these! If he thinks of it, it is an immediate object of thought while he thinks of it. If he doesn’t think of it, it isn’t an object of thought at all. Thus, every object of thought is an immediate object of thought, and the word ‘immediate’ joined to ‘objects of thought’ seems to be a mere filler.

(3) Though Malebranche and Berkeley believed that we have no ideas of minds or of the operations of minds, and that we can think and reason about them without ideas, this wasn’t Locke’s opinion. He thought •that there are ideas of minds and of their operations, as well as of the objects of sense, •that the mind perceives nothing but its own ideas, and •that all words are the signs of ideas.

(4) To suppose that Locke intended the word ‘immediate’ to limit the antecedent proposition is to attribute to him a blunder in reasoning that I don’t think he could have committed. It would consist in inferring from the premise

•ideas are among the objects of thought, but aren’t the only objects of thought

the conclusion

•all our knowledge has to do only with ideas.

You couldn’t come up with a more glaring invalidity than that! On the other hand, if he meant that ideas are the only objects of thought, then the inference he draws is perfectly sound and obvious; and he could just as well have said: Since ideas are the only things that the mind does or can contemplate, it is evident that our knowledge has to do only with them.

As to the conclusion itself, I have only to remark that although Locke says what he does only about knowledge (as he calls it) and not about judgment (as he calls it), there is the same reason for extending it to both. It is true of •judgment as well as of •knowledge that it must have to do with objects of the mind, or things that the mind can contemplate. Judgment, as well as knowledge, requires the conception of the object about which we judge; and it is obviously impossible to judge concerning objects that never were and never can be objects of the mind, ·because that would involve judging concerning objects of which one had no conception·.

So we can take it for granted that if knowledge has to do only with ideas, because there is no other object of the mind, it must be just as certain—and for the same reason—that judgment has to do only with ideas.

Locke adds, as the result of his reasoning: ‘Knowledge, then, seems to me to be nothing but the perception of the connection and agreement, or disagreement and mutual inconsistency, of any of our ideas. That is all it is.’ This is a very important point, not only •in itself but also •because of its necessary connection with his theory of ideas. The (a) thesis about knowledge and the (b) theory of ideas are connected in such a way that they must stand or fall together. If (a) falls, i.e. if there is any part of human knowledge that doesn’t consist in the perception of the agreement or disagreement of ideas, it must follow that (b) falls, i.e. that there are objects of thought and of contemplation that aren’t ideas.

So (a) the thesis about knowledge ought to be carefully examined. With this view let us first attend to its meaning. I don’t think it is likely to be misunderstood, but its meaning may need to be explained somewhat.

Every item of knowledge, and every judgment, is expressed by a proposition in which something is affirmed or denied of the subject of the proposition.

By perceiving ‘the connection or agreement’ of two ideas, I think Locke means perceiving the •truth of an affirmative proposition of which the subject and predicate are ideas. Similarly, by perceiving ‘the disagreement and mutual inconsistency’ of two ideas, I think he means perceiving the truth of a •negative proposition of which both subject and predicate are ideas. This seems to be the only meaning the words can bear, and it is confirmed by what Locke says in a passage already quoted a page back, where he equates ‘the mind takes its ideas to agree or disagree’ with ‘the mind takes a proposition to be true or false’. So if the definition of knowledge given by Locke is sound, the subject as well as the predicate of every proposition by which any item of •knowledge is expressed can only be an idea; and the same must hold for every proposition by which •judgment is expressed, as I have shown.

Having become clear about the meaning of this definition of human knowledge, we next have to consider how far it is sound.

·BRINGING IN THE ANCIENTS·

First, I would observe that •if ‘idea’ is taken in the meaning it had at first among the Pythagoreans and Platonists, and •if by ‘knowledge’ is meant only abstract and general knowledge (which I think Locke chiefly had in mind), I think it is true that such knowledge consists solely in perceiving the truth of propositions whose subject and predicate are ideas.

By ‘ideas’ here I mean things conceived abstractly without regard to their existence. We commonly call them ‘abstract notions’, ‘abstract conceptions’, ‘abstract ideas’; the Aristotelians called them ‘universals’; and the Platonists called them simply ‘ideas’, period, because they didn’t know of any other sorts of ideas.

Such ideas are both subject and predicate in every proposition which expresses abstract knowledge.

The whole body of pure mathematics is an abstract science; and in every mathematical proposition both subject and predicate are ‘ideas’ in the sense I am now exploring. [Reid explains this with examples, emphasizing that mathematics implies nothing about what exists. He adds that all so-called ‘demonstrative evidentness’ is found only in abstract knowledge. Demonstrations do occur in physical sciences, but always from premises that aren’t intuitively or demonstratively evident. Then:]

‘Ideas’, in the sense I am exploring, are creatures of the mind: they are constructed by its rational powers, and we know their nature and their essence because they are nothing more than they are conceived to be. And because they are completely known, we can reason about them with the highest degree of evidentness.

And because they are not things that exist, but things that are conceived, they don’t have place or time, and are not liable to change.

When we say that ideas are ‘in the mind’, all this can mean is that they are conceived by the mind, or that they are objects of thought. The act of conceiving them is, no doubt, in the mind ·in a more literal sense·; the things that are conceived have no place, because they have no existence. Thus a circle, considered abstractly, is said figuratively to be ‘in the mind’ of the person who conceives it; but in that sense it is also true that the city of London is ‘in his mind’ when he thinks about it.

Place and time belong to finite •things that exist, but not to things that are merely •conceived. They can be objects of conception to thinking beings in every place and at all times, which led the Pythagoreans and Platonists to think that ideas are eternal and omnipresent. If they had existence, that would have to be right, for they have no relation to any one place or time that they don’t have to every place and to every time.

The natural prejudice of mankind that what we conceive must have existence led those ancient philosophers to attribute existence to ideas, and that’s what led them into all the extravagant and mysterious parts of their system. When those parts are cleaned out, I think that what remains is the only intelligible and rational system about ideas.

I agree with them, therefore, that ideas are unchangeably the same in all times and places. For this means merely that a circle is always a circle and a square always a square.

I agree with them that ideas are the patterns or models by which every thing that had a beginning was made. For a thinking maker must conceive his work before making it, and he makes it according to that conception. And the thing that is conceived can only be an idea until it exists.

I agree with them that every species of things, considered abstractly, is an idea; and that the idea of the species is in every individual of the species, without being •divided or •multiplied—·i.e. without •being split into parts, one part for each individual, and without •generating a lot of ideas, one idea for each individual·. The point is just that the idea that is the species is an attribute, and to say that the idea ‘is in’ every member of the species is just to say that every member has the attribute. . . .

[Reid’s next few paragraphs mainly repeat things that he has said in Essay 5, chapter 1, with further emphasis on the restriction to necessary truths of the procedure of revealing truth through examining relations amongst ideas. Then:]

·BACK TO LOCKE·

Such is the nature of all truth that can be discovered by perceiving the agreements and disagreements of ideas, when we take ‘idea’ in its historically first sense. Locke in his definition of knowledge was mainly thinking about abstract truths, or so it seems from his illustrative examples.

But there is another great class of truths that are not abstract and necessary, and therefore can’t be perceived in the agreements and disagreements of ideas. They are the truths we know concerning the real existence of things—of our own existence, of the existence of other things—inanimate, animal, and rational—and of their various attributes and relations.

These may be called ‘contingent truths’. The only exceptions to that, so far as I know, are the truths about the existence and attributes of God, these being truths about existence that are nevertheless necessary.

All other things that exist depend for their existence, and for their detailed natures, on the will and power of ·God·, the first cause; so neither their existence nor their nature nor anything that happens to them is necessary; all of that is contingent.

But although the existence of God is necessary, I think that it’s only from contingent truths that we can deduce it. The only arguments for the existence of a Deity that I can understand are based on the knowledge of •my own existence and •the existence of other finite beings. And these are contingent truths.

So I believe that perceiving agreements and disagreements of ideas won’t lead us to knowledge of any contingent truth whatsoever, of the real existence of anything—not even of our own existence or the existence of a Deity, though that is a necessary truth. Thus, I have tried to show what knowledge can and what can’t be attained by perceiving the agreements and disagreements of ideas, when we take ‘idea’ in its historically first sense.

Now let us consider whether knowledge consists in perceiving the agreement or disagreement of ideas, when ‘idea’ is taken in any of the senses in which the word is used by Locke and other modern philosophers. ·There are three such senses to be considered·.

(1) Very often ‘idea’ is used so that •‘having the idea of’ something is a roundabout way of saying •‘conceiving’ it. In this sense, an idea is not an object of thought—it is thought itself. It is the act of the mind in which we conceive an object. Obviously this couldn’t be the meaning that Locke had in mind in his definition of knowledge.

(2) A second meaning of ‘idea’ is the one Locke gives early in his Essay, when he is apologising for how often he uses it: ‘It seems to be the best word to stand for whatever is the object of the understanding when a man thinks. . . .or whatever it is that the mind can be employed about in thinking’ (Essay I.i.8).

By this definition, indeed, everything that can be the object of thought is an idea. The objects of our thoughts can, I think, be put into two classes.

(a) The first class includes all the objects (that we can think of, and) that we believe to have a real existence. Objects such as the creator of all things, and all his creatures that we encounter. I can think of the sun and moon, the earth and sea, and of the various animal, vegetable, and inanimate productions with which God in his generosity has chosen to enrich our globe. I can think of myself, of my friends and acquaintances. I think of the author of the Essay with high esteem. These and their like are objects of the understanding that we believe to have real existence.

(b) A second class of objects of the understanding that a man may be employed about in thinking are things that we either •believe never to have existed or •think of without regard to their existence.

Thus I can think of Don Quixote, of the island of Laputa, of Oceana, and of Utopia, which I believe ·to be purely fictional, and· never to have existed. Every attribute, every species, and every genus of things, considered abstractly without any regard to their existence or non-existence, can be an object of the understanding ·in this second class·.

The label ‘idea’, taken in its historically first sense, very properly applies to this second class of objects of the understanding; and I have already considered what knowledge does and what does not consist in perceiving the agreements and disagreements of ideas of that sort.

But if we take ‘idea’ in such a broad sense that it covers not only (b) the second class but also (a) the first class of objects of the understanding, it will undoubtedly be true that all knowledge consists in perceiving the agreements and disagreements of ideas. For there can’t possibly be any knowledge, any judgment, any opinion (true or false) that isn’t employed about the objects of the understanding. But whatever is an object of the understanding is an ‘idea’, according to this second meaning of the word.

Yet I am convinced that Locke in his definition of knowledge didn’t mean ‘idea’ to cover all the things that we commonly consider as objects of the understanding.

Though Berkeley believed that the sun, moon, and stars, and all material things are ideas and nothing but ideas, Locke nowhere expresses this opinion. He believed that we have ideas of bodies, but not that bodies are ideas. He believed that we have ideas of minds, but not that minds are ideas. When he inquired so carefully into the origin of all our ‘ideas’, he surely didn’t mean •to learn the origin of everything that can be the object of the understanding, or •to conclude that the origin of everything that can be an object of that understanding lies in sensation and reflection!

(3) So neither of those two meanings of ‘idea’—·the ones here labelled (1) and (2)·—can be what Locke had in mind in his definition of knowledge. So the only meaning he could have intended in that definition is the one that I earlier called ‘the philosophical meaning of “idea”’, referring to the commonly accepted theory about how the mind perceives external objects, and how it remembers and conceives objects that are not present to it [Essay 1, chapter 1]. It is a very ancient opinion, and has been very generally accepted among philosophers, that we can’t perceive or think of such objects •immediately, and have to perceive or think of them •through the medium of certain images or representatives of them that really exist in the mind at the time.

The ancients called those images ‘species’ and ‘phantasms’. Modern philosophers have named them ‘ideas’. Locke writes:

Obviously the mind knows things not immediately but only through the intervention of its ideas of them. (Essay IV.iv.3)

And in the same section he puts this question:

How shall the mind, which perceives nothing but its own ideas, know that they agree with things themselves?

I have already considered this theory when discussing •perception, •memory, and •conception. You will find there the reasons why I think

•that this theory has no solid foundation in reason or in attentive reflection on •those operations of our minds,

•that it contradicts the immediate dictates of our natural faculties, which have more authority than any theory;

•that it has arisen from the same prejudices that led all the ancient philosophers to think that God couldn’t make this world without some eternal matter to work on, and led the Pythagoreans and Platonists to think that God couldn’t conceive the plan of the world he was to make without eternal ideas really existing as patterns to work by; and

•that this theory, when its consequences are competently thought through, leads to absolute scepticism, though those consequences weren’t seen by most of the philosophers who have adopted the theory.

I shan’t repeat what I have already said on those points. All I shall do, taking ‘ideas’ in this sense, is to make some observations on Locke’s definition of knowledge. ·On this I have two main things to say·.

(1) If all knowledge consists in perceiving the agreements and disagreements of ideas, i.e. of representative mental images [= ‘likenesses’] of things, it obviously follows that if there are no such ideas there can’t be any knowledge. So that if we found good reason for giving up this philosophical hypothesis, all knowledge would have to go along with it.

I hope, however, that it is not so, and that even when this hypothesis ·about ideas· staggers and falls to the ground—as many other hypotheses have done—knowledge will continue to stand firm on a more permanent basis.

The cycles and epicycles of the ancient astronomers were, for a thousand years, thought to be absolutely necessary to explain the motions of the heavenly bodies. [The underlying assumption was that heavenly bodies must move in circles. To square this with increasingly precise observations, it was supposed that sometimes a planet moves in a circle with epicycles, i.e. circles within the big circle; and sometimes epicycles within the epicycles.] But now, when all men believe them to have been mere fictions, astronomy has not fallen with them but stands on a more rational foundation than before. Ideas, or mental images of things existing in the mind, have for an even longer time been thought necessary for explaining the operations of the understanding. If they should also at last be found to be fictions, human knowledge and judgment would suffer nothing from being detached from this unwieldy hypothesis. Locke surely didn’t look on the existence of ideas as a philosophical hypothesis: he thought that we are conscious of their existence, otherwise he wouldn’t have made the existence of all our knowledge depend on the existence of ideas.

(2) If this hypothesis is true, I agree with Locke that it is an obvious and necessary consequence that our knowledge can have to do only with ideas, and must consist in perceiving their attributes and relations. (Everything we can know about any object must be either some attribute that it has or some relation it bears to some other object or objects. ·Locke would accept this; by the ‘agreements and disagreements’ of objects, I think he meant both their attributes and their relations·.) For nothing can be more obvious than this: all knowledge and all judgment and opinion must be about things that are or could be immediate objects of our thought. What can’t be the object of thought, or the object of the mind in thinking, can’t be the object of knowledge or of opinion.

So if •ideas are the only objects of thought, it inevitably follows that •they are the only objects of knowledge, and all knowledge consists in perceiving their agreements and disagreements, i.e. their attributes and relations. The use I want to make of this inference is to show that the hypothesis which is its premise must be false: •we do have knowledge of things that are not ideas, so it inevitably follows that •ideas are not the only objects of our thoughts.

Locke in Essay IV has pointed out the extent and limits of human knowledge with more precision and judgment than any philosopher had done before him; but he doesn’t there confine knowledge to the agreements and disagreements of ideas. And I can’t help thinking that a great part of the Essay is a knock-down refutation of the principles laid down at the beginning of it.

[Reid remarks that Locke thought he had ‘some certain knowledge’ about all sorts of things that he didn’t think to be ideas—himself, his friends, God, the earth and the sea, etc. His knowledge about those can’t consist in perceptions of the agreements and disagreements of ideas. He ought to have thought that, since ideas are the only objects of thought, there can’t be any knowledge of the existence of ourselves or of external objects or of God. Berkeley accepted that inference as it applies to external objects; he preferred •accepting that there can be no knowledge of them to •dropping the theory of ideas from which that follows. But he didn’t accept the inference as it applies to minds and God; he held that we can think of them without ideas. Then:]

Hume saw very clearly •the consequences of this theory ·of ideas·, and adopted •them in his theorizing moments; but he openly admits that in everyday life he found himself compelled to believe with the vulgar. [This alludes to Berkeley’s remark that on some of these matters we should ‘think with the learned and speak with the vulgar’.] His Treatise of Human Nature is the only system to which the theory of ideas leads; and in my view every part of it necessarily follows from of that theory.

But Locke didn’t see all the consequences of the theory; he adopted it without doubt or examination, swept along by the stream of philosophers that went before him; and his judgment and good sense have led him to say many things, and to believe many things, that can’t be reconciled with it.

He not only believed in his own existence, the existence of external things, and the existence of a God, but he has shown very soundly how we come by the knowledge of these existences. You might expect him to point out the agreements and disagreements of ideas from which these existences are deduced, but that is impossible, and he doesn’t even try.

Our own existence, he says, we know intuitively; but this intuition is not a perception of the agreement or disagreement of ideas, because the subject of the proposition I exist is not an •idea but a •person.

The knowledge of external objects of sense, Locke says, can be had only through ‘sensation’. He later spells out ‘sensation’ into ‘the testimony of our senses, which are the proper and sole judges of this thing’, their testimony being ‘the greatest assurance we can possibly have, and the greatest our faculties are capable of’. This fits perfectly well with the common sense of mankind, and is perfectly understood by those who never heard of the theory of ideas. Our senses testify immediately to the existence, and many of the attributes and relations, of external material things; and we are so built that we confidently rely on their testimony, without seeking a reason for doing so. This assurance, Locke accepts, deserves to be called ‘knowledge’. But those external things are not ideas, and their attributes and relations are the agreements and disagreements not of •ideas but of •things that are not ideas.

To reconcile this to the theory of ideas, Locke says that ‘it is the actual receiving of ideas from outside us that gives us notice of the existence of those external things’. If we take ‘receiving ideas from outside us’ literally, this takes us back to Aristotle’s doctrine that our ideas or ‘species’ come from the external objects, and are the likenesses or forms of those objects. But I don’t think that Locke meant it literally; I believe he meant merely that our ideas of sense must have a cause, and that we are not the cause of them ourselves.

Berkeley acknowledges all this, and shows very clearly that •it doesn’t present the least shadow of a reason for believing in any material object—indeed, that •there can’t be anything external that in any way resembles our ideas except the ideas of other minds.

It is evident therefore that the agreements and disagreements of ideas can give us no knowledge of the existence of any material thing. . . .

As to the existence of a god, though Locke was aware that Descartes and many after him had tried to prove it merely from the agreements and disagreements of ideas, he thought that ‘if you want to establish this truth and silence atheists, you are going about it in a poor way if you lay the whole stress of so important a point as this on that one foundation’ (Essay IV.x.7). So instead he argues for the existence of a god, with great strength and solidity, from our own existence and the existence of the perceptible parts of the universe.

By memory, Locke says, we have knowledge of the past existence of many things. But all conception of past existence, as well as of external existence, conflicts with the theory of ideas by requiring that there be immediate objects of thought that are not ideas existing right now in the mind.

I conclude, therefore, that if we have any •knowledge of the existence of ourselves, of what we see around us, or of a god, or if we have any •knowledge of past things through memory, that •knowledge can’t consist in perceiving the agreements and disagreements of ideas.

[Reid remarks that this is self-evident, and gives reasons for saying so—reasons that repeat things he has said in the past few pages. Then:]

There can’t be any •knowledge, •judgment, or •opinion about things that aren’t immediate objects of thought. I regard this as self-evident. So if ideas are the only immediate objects of thought, they must be the only things in Nature of which we can have any knowledge and about which we can have any judgment or opinion.

Hume saw this inevitable consequence of the common doctrine of ideas, and he made it evident in his Treatise of Human Nature; but what he used it for was not to •overturn the theory from which it necessarily follows, but rather to •overturn all knowledge, leaving no basis for believing anything whatsoever. If Locke had seen this consequence, there is reason to think that he would have used it differently!

It does seem strange that a man of Locke’s judgment and penetration didn’t see such an obvious consequence. The only way I can explain it is this: the ambiguity of ‘idea’ has misled him, here as in several other places. Having at first defined ‘ideas’ to be

•‘whatever is the object of the understanding when we think’,

he very often takes it in that unlimited sense—so that everything that can be an object of thought is ·automatically· an idea. At other times he uses ‘idea’ to signify

•certain representative images of things in the mind, which philosophers have supposed to be immediate objects of thought.

At other times ‘ideas’ are

•things conceived abstractly, without regard to their existence.

Philosophy is much indebted to Locke for his discussion of the misuse of words. It is pity he didn’t apply the discussion to the word ‘idea’, the ambiguity and misuse of which has very much hurt his excellent Essay.

I don’t think I need to say much about certain other opinions of philosophers concerning judgment.

Hume sometimes adopts Locke’s opinion that judgment is the perception of the agreement or disagreement of our ideas; sometimes he maintains that judgment and reasoning resolve themselves into •conception, and are nothing but particular ways of conceiving objects; and ·in this spirit· he says that an opinion or belief can most accurately be defined as ‘a lively idea related to or associated with a present impression’ (Treatise I.iii.7). I tried to show in chapter 1 of this Essay that judgment is a mental operation of mind of a quite different kind from the bare conception of an object [here]. I also considered Hume’s notion of belief when discussing theories about memory ·in Essay 3, chapter 7·.

[Reid then •quotes a passage from Hartley which he says expresses the same position as Hume’s, •quotes a passage from Priestley which he says expresses the same position as Locke’s, and •says that many detailed points about judgment might be made, but they ‘are to be found in every system of logic from Aristotle down to the present age’.]

Chapter 4: First principles in general

One of the most important distinctions within our judgments is that between •intuitive judgments and •judgments based on argument.

It is not in our power to judge as we will. The ·faculty of· judgment is carried along irresistibly by the evidentness— real or illusory—that appears to us at the time. But propositions that are submitted to our judgment fall into one or other of two great classes. (1) Some are of such a nature that a man of mature understanding can grasp them firmly and perfectly understand their meaning, without finding himself compelled to believe them to be true or false, probable or improbable. In these cases, the ·faculty of· judgment remains in suspense until it is inclined to one side or another by reasons or arguments. (2) Other propositions are no sooner understood than they are believed. Our •taking them in leads unstoppably to our •judgment on them, and these two ·mental operations· are equally the work of Nature and the result of our basic powers. There is no searching for evidence, no weighing of arguments; the proposition is not deduced or inferred from another; it has the light of truth in itself, and has no occasion to borrow it from another proposition.

Propositions of kind (2), when they are used in matters of science, have commonly been called ‘axioms’; and in all sorts of contexts of their use they are called

first principles

principles of common sense

common notions

self-evident truths.

[Reid quotes Cicero and Shaftesbury for some other labels for them. Then:]

What I have said is sufficient, I think, to distinguish (1) first principles or intuitive judgments from (2) judgments that can be ascribed to the power of reasoning. And this distinction isn’t harmed if there are some judgments concerning which we may be unsure whether they belong in (1) or in (2). There is a real distinction between people inside the house and people outside the house, yet we may be unsure on which side of the distinction we should put the man who stands on the door-step!

The power of reasoning—i.e. of drawing a conclusion from a chain of premises—may properly enough be called an ‘art’. ‘In all reasoning’, says Locke, ‘we search and flail around, having to take pains and stick to the problem’ (Essay I.ii.10). The power to reason resembles the power of walking, which is acquired by use and exercise. Nature prompts us to it, and has given us the power of acquiring it; but we can’t actually walk until we have worked at it. After repeated efforts, much stumbling, and many falls, we •learn to walk; and that is like how we •learn to reason.

But with clearly understood self-evident propositions, the •power of judging can be compared to •the power of swallowing our food. It is purely natural, and therefore common to the learned and the uneducated, to the trained and the untrained. It requires maturity of understanding and freedom from prejudice, but nothing else.

I take it for granted that there are self-evident principles. Nobody, I think, denies this. If anyone was so sceptical as to deny that any proposition is self-evident, I don’t see how we could convince him by reasoning.

But there seem to be great differences of opinion among philosophers about first principles. One philosopher •takes to be self-evident a proposition that a second •labours to prove by arguments and a third •denies altogether. Consider for example the proposition that

There is a sun, moon, earth, and sea which really exist, whether or not we think of them.

Before Descartes’s time, that was taken to be a first principle. Descartes thought that it ought to be proved by argument; and in this he was been followed by Malebranche, Arnauld, and Locke. They all laboured to prove, by very weak reasoning, the existence of external objects of sense; and Berkeley and Hume, aware of the weakness of those arguments, were led to deny the existence of the sun etc. altogether.

The ancient philosophers granted that all knowledge must be based on first principles, and that there is no reasoning without them. Rather than having too few ‘first principles’, the Aristotelian philosophy had too many. Perhaps the misuse of them in that ancient system is what brought them into discredit in modern times;. . . .and as one extreme often leads to the opposite extreme, this seems to have been the case with the ancient and the modern attitudes to first principles.

Descartes thought that one principle, expressed in one word cogito—‘·I think·’—was a sufficient foundation for his whole system, and he asked for no more.

Locke seems to think that first principles are very little use. Holding that knowledge consists in the perception of the agreement or disagreement of our ideas, he thought that when we have clear ideas and can compare them with one another, we can always fabricate first principles as often as we need them. Such differences we find among philosophers about first principles.

A question of some importance is this: When men disagree about first principles, can the disagreements be resolved? What actually happens in most such disputes is that one man maintains something as a first principle which another man denies, both parties •appeal to ‘common sense’, and there the matter rests. Isn’t there some way of discussing this •appeal? Isn’t there some mark or criterion by which to distinguish genuine first principles from purported first principles that really are not so? I shall humbly offer, in the following ·four· propositions, what appears to me to square with the truth in these matters, though I am always open to being convinced that I should change my opinion.

(1) All knowledge acquired by reasoning must be built on first principles. I hold this to be certain, and even demonstrable.

It is as certain as that every house must have a foundation. The •power of reasoning in this respect resembles •mechanical powers or engines: ·like them·, it must have a fixed point to rest on, because otherwise it spends its force in the air and produces no effect.

[In most of this work, Reid has taken ‘analysis’ to stand for a process of intellectually taking something apart, but we are about the meet ‘analytic’ in a different sense that is now obsolete. In this sense, an ‘analytic’ procedure is one that works from effects back to causes, from what is given to what explains it, from conclusions back to premises; and a ‘synthetic’ procedure, in the related sense, is one that goes in the reverse direction.]

When we examine in an analytic way the evidentness of any proposition, either we find it to be self-evident or ·we find that· it rests on one or more propositions that support it. The same holds for those supporting propositions, and of the supports of their supports,. . . as far back as we can go. But we can’t go back along this track to infinity. So where is this analysis of ours to stop? Obviously, it can’t stop until we come to propositions that •support all the others that are built on them but are themselves •not supported by any—i.e. until we come to self-evident propositions.

Now consider a synthetic proof of some kind, where we start with the premises and pursue a series of consequences until we eventually come to the last conclusion, the thing to be proved. In this procedure we must begin either with •selfevident propositions or with •ones that have been already proved. In the latter case, the proof of those propositions is a silent part of our proof, which is deficient without it. Well, suppose that that deficiency is remedied and our proof is completed: isn’t it obvious that it must set out with self-evident propositions, and that the evidentness of the conclusion must rest on them? So it seems to be demonstrable that •without first principles analytic reasoning could have no end, and synthetic reasoning could have no beginning; and that •every conclusion reached through reasoning must rest its whole weight on first principles, as a building does on its foundation.

(2) Some first principles yield conclusions that are certain, others such as are probable in various degrees from the highest probability to the lowest.

In valid reasoning, the strength or weakness of the conclusion will always correspond to the strength or weakness of the principles on which it is based.

Where it’s a matter of testimony, it is self-evident that testimony from two people is better than testimony from one, provided that the two are on a par in their characters and their access to knowledge; but the testimony of one person may be true, and testimony that is preferred to it—·e.g. the contrary testimony of two others·—may be false.

When an experiment has succeeded in several trials, and the circumstances have been noted with care, there is a self-evident •probability that it will succeed in a new trial; but there is no •certainty. The level of probability varies in different cases, because cases vary in how easy it is to observe all the circumstances that may influence the outcome. And even when many experiments have been made with care, our expectation may be frustrated in the very next trial, because of some difference in the circumstances that hasn’t been—perhaps couldn’t have been—observed.

Newton laid this down as a first principle in natural philosophy:

A property that has been found in all bodies that we have been able to test, and that has always been found in its quantity to be in exact proportion to the quantity of matter in the body in question, is to be regarded as a universal property of matter.

This principle has never been questioned, as far as I know. The evidence we have that all matter is divisible, movable, solid, and inert all relies on this principle. If the principle isn’t true, we can’t reasonably believe that all matter has those properties. From the same principle that great man has shown that we have reason to conclude that all bodies gravitate towards each other.

But this principle doesn’t have the kind of evidentness that mathematical axioms have. It isn’t—and Newton never thought it to be—a necessary truth whose contrary is impossible. And if it were ever discovered through sound experiments that some parts of some bodies don’t have gravity, that fact would have to be accepted as an exception to the general law of gravitation.

In games of chance, it is a first principle that •every side of a die has an equal chance to be turned up; and that in a lottery •every ticket has an equal chance of winning. From such first principles as these, which are the best we can have in such matters, we can infer by demonstrative reasoning the precise degree of probability of every possible outcome in such games.

But the principles on which all this precise and deep reasoning is based can never yield a certain conclusion, for you can’t make up for a defect in the first principles by any excellence in the reasoning based on them. Just as water, however skillfully channelled, can’t rise higher than its source, so also no conclusion of reasoning can be more evident than the first principles from which it is inferred.

(3) It would contribute greatly to the stability of human knowledge, and consequently to increasing it, if the first principles on which the various parts of it are based were pointed out and ascertained.

We have reasons to accept this, both from facts and from the nature of the thing [by which, as we shall see in a moment, Reid means ‘both from empirical reasons and from ones based on abstract theoretical points’].

·‘FROM THE FACTS’·

Mathematics and natural philosophy are two branches of human knowledge in which this method has been followed, ·i.e. whose basic principles have been pointed out and ascertained·. This has been done in mathematics as far back as we have books. This science is the only intellectual area which, in more than two thousand years, has generated no sects, no conflicting systems, and hardly any disputes—and any disputes there have been have ended, for good, as soon as the animosity of parties subsided. The science once firmly established on the basis of a few axioms and definitions, as though on a rock, has grown through the centuries so as to become the highest and firmest structure that human reason can boast.

Until less than two hundred years ago, natural philosophy remained in the same fluctuating state as the other sciences. Every new system pulled up the old ones by the roots. The system-builders were indeed always willing to get help from first principles when they were on their side; but, finding them insufficient to support the structure that their imagination had raised, they brought them in only as helps, mixing with conjectures and with lame inductions, so that the resultant systems were like the statue of Nebuchadnezzar with its feet made partly of iron and partly of clay.

Bacon first set out the only solid foundation on which natural philosophy can be built; and Newton boiled Bacon’s principles down into three or four axioms that he calls ‘rules of philosophising’. From these, together with the phenomena observed by the senses (which he also lays down as first principles), Newton infers by strict reasoning the propositions contained in the third book of his Principia and in his Optics; and in this way he has built in those two branches of natural philosophy a structure that is not open to being shaken by doubtful disputation, and stands immovable on the basis of self-evident principles.

This structure has been further developed by the arrival of new discoveries, but it is no longer subject to revolutions.

We are now done with the disputes about prime matter, substantial forms, Nature’s abhorring a vacuum, and bodies’ having no gravitation when they are in their proper place. The builders in this work don’t have to build with only one hand because they are holding a ·defensive· weapon in the other! All they have to do is to carry on the work.

Yet it seems very probable that if natural philosophy hadn’t been raised on this solid foundation of self-evident principles, it would have remained to this day a battle-field on which every inch of ground was disputed and nothing was permanently settled.

Admittedly, natural philosophy and (especially) mathematics have an advantage over most other sciences, namely that in them it is easier to form clear and definite conceptions of the objects that they are dealing with. But the difficulty that other sciences have about this can be overcome. It could explain why they have had a longer infancy, but it gives no reason why they can’t eventually reach maturity by the same steps as were taken by the two sciences that grew up faster.

These facts may lead us to conclude that if in other branches of philosophy the first principles were laid down as has been done in mathematics and natural philosophy, and the subsequent conclusions were based on them, this would make it much easier to distinguish what is solid and well supported from the vain fictions of human fancy.

·‘FROM THE NATURE OF THE THING’·

But quite apart from ·empirical· facts, the nature of the thing leads to the same conclusion.

For when any system is based on first principles, and is deduced from them in a way that conforms to the ·logical· rules, we have a thread to lead us through the labyrinth. Our judgment has a clear and definite object. The ·three· different parts ·of the system· can be separated, so that each can be examined in isolation.

The whole system comes down to •axioms, •definitions, and •deductions. These are very different materials, which have to be evaluated by very different standards; and judging each in isolation is much easier than judging a mass in which they all mixed together without distinction. Let us consider how we judge each of them.

(3.1) As to •definitions, it is very easy. They relate only to words; and if people mean different things by some word, and each sticks to his own meaning, that will produce different ways of speaking but it can’t ever produce different ways of thinking.

Still, when in the course of reasoning men use the same word sometimes in one sense and sometimes in another, this produces fallacies—nothing produces more fallacies than it does! And the best way of preventing such fallacies, or of detecting them when they occur, is to have definitions of words that are as precise as possible.

(3.2) As to •deductions from principles that are accepted by both sides ·in a scientific dispute·, I don’t see how they—·i.e. the deductions·—can be a subject of dispute for long, among men who aren’t blinded by prejudice or bias. For the rules of reasoning by which conclusions can be inferred from premises have been fixed with great unanimity for two thousand years. No-one man disputes the rules of reasoning laid down by Aristotle and repeated by every writer on practical logic.

I would point out, by the way, that the reason why logicians from •Aristotle down to this day have been so unanimous in settling on the rules of reasoning seems to be that •that great genius derived them in a scientific manner from a few definitions and axioms. I add that when men differ about whether a certain conclusion follows from certain premises, I think it is always because they differ about some first principle. I shall explain this by an example.

Suppose that from a thing’s having begun to exist one man infers that it must have had a cause, while another man doesn’t accept that inference. It is obvious in this case that one man does, while the other doesn’t, take it to be a self-evident principle that everything that begins to exist must have a cause. If they settle this point, their dispute will be at an end.

Thus I think it appears that in matters of science if •the terms are properly explained, •the first principles on which the reasoning is based are laid down and exposed to examination, and •the conclusions are deduced from them in a way that conforms to the ·logical· rules, it might be expected that fair-minded and able men who love truth and have patience to examine things coolly would reach unanimity about the validity of the inferences, so that their only differences would be ones concerning first principles.

(4) When fair-minded and honest people happen to differ about first principles, Nature has equipped us with means by which to bring them to unanimity.

When men differ about things that are taken to be first principles or self-evident truths, reasoning seems to be at an end. Each party appeals to common sense. When one man’s common sense gives one answer and another man’s gives a conflicting answer, there seems to be no way out except to leave everyone to enjoy his own opinion. This is often said, and I think it is true if rightly understood.

It is useless to reason with someone who denies the first principles on which the reasoning is based. Thus it would be useless to try to prove a proposition in Euclid to someone who denies Euclid’s axioms. Indeed we ought never to reason with men who deny first principles because they are obstinate and unwilling to yield to reason.

But isn’t it possible that men who really love truth and are open to conviction may differ about first principles?

I think it is possible, and that it would show a great lack of charity if one said that it isn’t. (·Saying that it isn’t possible is tantamount to saying ‘If someone disagrees with me about first principles, he doesn’t really love truth and is obstinately determined not to yield to reason’—which shows a lack of charity·.)

When this kind of disagreement occurs, everyone who believes that there is a real distinction between truth and error, and that the faculties God gave us aren’t inherently deceptive, must be convinced that there is a defect or a perversion of judgment on one side or the other.

A fair-minded and humble man who is party to such a disagreement will naturally have enough doubt about his own judgment to want to conduct a serious examination of propositions that he has been regarding—perhaps for many years—as first principles. He will think it possible that although his heart is upright his judgment may have been twisted by education, by authority, by party zeal, or by some other of the common causes of error—causes that can influence even the able intellects of honest people.

When someone is in that frame of mind, so unaggressive and so suitable to every good man, has Nature left him with no rational means either to correct his judgment if it is wrong or to confirm it if it is right? I hope not. . . .

In other kinds of controversy, the procedure by which the truth of a proposition is discovered (or its falsehood detected) is to show that it is necessarily connected with (or inconsistent with) first principles; but when the controversy is about whether a proposition is a first principle, this procedure can’t be followed. In controversies of this kind, therefore, truth has a special disadvantage. But it has ·three· advantages of another kind to make up for this.

(4.1) In controversies about first principles, everyone is a competent judge; and that makes it hard for anyone to deceive mankind.

To form a judgment about first principles, all you need is a sound mind free from prejudice, and a clear conception of the question. The learned and the uneducated, the philosopher and the day-labourer, are on a level ·in this respect·, and they’ll pass the same judgment unless they are misled by some bias or taught to renounce their own understandings from some mistaken religious principle.

In matters that are beyond the reach of common understanding, the many are led by the few, and willingly yield to their authority. But in matters of common sense, the few must yield to the many when local and temporary prejudices are removed. No man is now moved by the subtle arguments of Zeno against ·the possibility of· motion, even if he doesn’t know how to answer them.

The ancient form of scepticism furnishes a remarkable instance of this truth. That system, said to have been invented by Pyrrho, was carried down through a succession of ages by very able and acute philosophers who •taught men to believe nothing at all and •regarded it as the highest achievement of human wisdom to withhold assent from absolutely every proposition. It was supported with great subtlety and learning. . . . The assault of the sceptics against all science seems to have been managed with more skill and nimbleness than the defence of ·science by· the dogmatists.

But because this scepticism was an insult to the common sense of mankind it died without having to be killed, and it would be useless to try to revive it. Modern scepticism is very different from the ancient version, otherwise it wouldn’t have been given a hearing; and when it has lost the charm of novelty it will die too even if it isn’t ever refuted.

Modern scepticism—I mean the scepticism of Hume—is built on principles that were very generally maintained by philosophers who didn’t see that they led to scepticism. Hume, by tracing with great acuteness and ingenuity the consequences of generally accepted principles, has shown that those principles overturn all knowledge, and eventually overturn themselves, leaving the mind in perfect suspense.

(4.2) Opinions that contradict first principles are distinguished from other errors by being not merely false but absurd. And Nature has given us a particular device for showing up and embarrassing absurdity, namely the emotion of ridicule, which seems intended for this very purpose of putting to shame anything that is absurd either in opinion or practice.

This weapon, when properly wielded, cuts with as sharp an edge as argument does. Nature has provided us with •ridicule to expose •absurdity, and with •argument to refute •error. Both are well fitted for their different jobs, and are equally friendly to truth when properly used.

Both may be misused in the service of error. But the degree of judgment that serves to detect the misuse of argument in false reasoning is also adequate to detect the misuse of ridicule when it is wrongly directed.

[Reid then discusses some factors that may disguise absurdity, thus shielding it from ridicule: intense religious feelings, the ‘gravity and solemnity’ with which the absurdity is presented, the stature of the author of the absurdity, the charm of novelty, the fact that the absurdity is something we have accepted since we were children. Then:] But an absurdity can be taken seriously by sensible people only while it wears a mask. As soon as someone has the skill or the boldness to pull off the mask, it can no longer bear the light; it slinks into dark corners for a while, and is never heard of again except as something to laugh at.

(4.3) Just because first principles are first principles, they can’t be directly or demonstratively proved; but there are certain ways of reasoning about them which confirm the ones that are sound and solid and detect the ones that are false. I shall describe ·five of· these ways of reasoning.

(4.3.1) If it is shown that a first principle that a man rejects stands on the same footing with others that he accepts, this is a good argument ad hominem. [Latin = ‘against the man’; an argument ad hominem against proposition P as held by person x purports to show not that •P is false but that •x is not in a position to accept P.] For when this is the case, he is guilty of an inconsistency in holding one and rejecting the other.

Here is an example. The faculties of •consciousness, •memory, •external senses, and •reason are all equally gifts of Nature. Any good reason that can be given for accepting the testimony of one of them is an equally good reason for accepting the testimony of all the others. The greatest sceptics accept the testimony of •consciousness, and allow that what it testifies is to be held as a first principle. So if they reject the immediate testimony of •the senses or of •memory, they are guilty of an inconsistency.

(4.3.2) A first principle may admit of a proof ad absurdum.

In this kind of proof, which is very common in mathematics, we prove the proposition P by supposing not-P and tracing the consequences of that in a course of reasoning; if we find any of not-P’s inevitable consequences to be obviously absurd, we conclude that not-P is false and therefore that P is true.

Very few propositions—and extremely few propositions that are candidates for the role of first principles—stand alone and unconnected. A proposition draws many others along with it, in a chain that can’t be broken. Someone who takes up a proposition must bear the burden of all its consequences; and if that burden is too heavy for him to carry, he must set down—·i.e. no longer accept·—that proposition.

(4.3.3) The consent of ages and nations, of the learned and the uneducated, should have great authority regarding first principles, where everyone is a competent judge.

First principles are a basis not only for •our theorizing in philosophy but also for •our ordinary conduct in life; and every motive to action presupposes some belief. When we find that men generally agree about principles that concern human life, this must have great authority with every sober mind that loves truth.

Berkeley tried to show that his theory asserting the non-existence of a material world didn’t contradict the views of the vulgar, but only those of the philosophers. With good reason, he was more afraid of opposing the authority of vulgar opinion in a matter of this kind than of opposing all the schools of philosophers. But when we watch his doomed attempt to reconcile his system with vulgar opinion, we can only be amused.

You may say: ‘What has authority to do with matters of opinion? Is truth to be determined by votes? Is authority to be raised out of its grave so that it can again tyrannise over mankind?’ I’m aware that these days an advocate for authority has an unpopular case to make, but I don’t want to give to authority any more than its due.

Quite rightly we honour the names of the benefactors of mankind who have helped to break the yoke of the authority that deprives men of their natural and unalienable right to judge for themselves; but while we are rightly hostile to that kind of authority and to everyone who wants to subject us to its tyranny, let us remember how common the folly is of going from one fault to the opposite extreme—·in this case, escaping from one kind of authority and rushing to the opposite extreme of rejecting all kinds of authority·.

Authority, though a very tyrannical •master of private judgment, may yet sometimes be a useful •servant; that is all it is entitled to and all that I claim for it. To see that I am right about this, let us consider a possible case in mathematics, the science where everyone agrees that authority has less weight than in any other.

Suppose a mathematician makes a discovery that he thinks is important, puts his demonstration of it in the proper order, and after examining it carefully finds no flaw in it. Won’t he still hold back a little, having some fear that the thrill of discovery may have made him overlook some false step? This must be granted.

He submits his demonstration to the examination of a mathematical friend whom he thinks to be a competent judge, and impatiently waits to hear his judgment. Won’t the favourable (or unfavourable) verdict of his friend greatly increase (or lessen) his confidence in his own judgment? Most certainly it will, and so it should.

If •his friend’s judgment agrees with his own—and especially if it is confirmed by two or three ·other· able judges—he becomes sure about his discovery, without further examination; but if •it is unfavourable, he is has to suspend judgment again, until the suspect part of the demonstration is examined again more rigorously. . . . Here we see a man’s judgment, even about a mathematical demonstration,

•conscious of some feebleness in itself,

•seeking the aid of authority to support it,

•greatly strengthened by that authority, and

•hardly able to stand up to it without some new aid.

When people who are regarded as fair and competent judges agree in their judgment on some matter, that creates a kind of •judgment society, which has effects very similar to those of •civil society: it gives strength and courage to every individual, and removes the anxiety that accompanies •solitary judgment as naturally as it accompanies a •solitary man in the state of Nature. So we should judge for ourselves while also being willing to get help from the authority of other competent judges. . . . Regarding a matter of common sense, everyone is as competent a judge as a mathematician is regarding a mathematical demonstration; and there must be a great presumption that the judgment of mankind in such a matter is the natural output of the faculties that God has given us. Such a judgment can be wrong only when there is some cause of the error that is as general as the error is. When this can be shown to be the case, I accept that it ought to have its due weight. But it is highly unreasonable to suppose that mankind in general, in accepting something self-evident, have deviated from the truth although no cause for the deviation can be given.

You may think: ‘It is impossible to collect the opinion of men in general on any point whatsoever. So the “authority” of their general opinion can’t give us any help in examining first principles.’ I reply that in many cases this is not impossible, and not even difficult.

Who can wonder whether men have universally believed

•in the existence of a material world?

•that every change that happens in Nature must have a cause?

•that there is a right and a wrong in human conduct; some things that merit blame and others that are entitled to approval?

The universality of these opinions, and of many others like them that I could name, is sufficiently evident from the whole tenor of human conduct as we have experienced it and learned about it from history.

There are other opinions that appear to be universal from what is common in the structure of all languages. [Reid develops this point, repeating things he has said more than once before, starting with Essay 1, chapter 1.]

(4.3.4) Opinions that appear so early in the minds of men that they can’t be the effect of education or of false reasoning have a good claim to be considered as first principles. Consider, for example, our belief that the people around us are living and thinking beings. Perhaps when we become able to reason we can give some reason for this; but we believed it before we could reason, and before we could learn it by being taught it. It seems, therefore, to be an immediate effect of our constitution.

(4.3.5) When an opinion is so necessary in the conduct of life that without it a man will be led into a thousand absurdities in his behaviour, such an opinion can safely be regarded as a first principle, even if we can give no other reason for it. . . .

Chapter 5: The first principles of contingent truths

Berkeley writes: ‘Surely it is well worth the trouble to make a strict enquiry into the first principles of human knowledge, to sift and examine them on all sides’ (Principles, Introduction 4). What I said in the last chapter is intended both to show the importance of this enquiry, and to make it easier.

But such an enquiry can’t actually be made until the first principles of knowledge have been separated out from other truths and exhibited for us to inspect them, so that they can be ‘sifted and examined on all sides’. For that purpose I shall try to list the truths that I take to be first principles, and to give my reasons for thinking that that’s what they are.

Some readers may think that my list contains things that shouldn’t be there; others may think that some first principles are missing from the list; others again may have both complaints. Things that I take to be first principles may strike some people as vulgar errors, or as truths that stem from other truths and are therefore not first principles. Well, in these matters everyone must judge for himself! If I see a list that is better than mine in any or in all of those respects, I shall rejoice! I am convinced that the agreement of honest men of judgment concerning first principles would do as much for the advancement of knowledge in general as the agreement of mathematicians concerning the axioms of geometry has done for the advancement of that science.

The truths that fall within the scope of human knowledge, whether they are self-evident or deduced from ones that are self-evident, fall into two classes: •necessary and unchangeable truths, whose contrary is impossible, and •contingent and changeable truths that depend on some effect of will and power that had a beginning and may have an end.

That a cone has one third of the volume of a cylinder with the same base and the same height is a necessary truth. It doesn’t depend on the will and power of anyone or anything. It is unchangeably true, and its contrary is impossible. That the sun is the centre around which the earth and the other planets of our system revolve is a truth; but it isn’t a necessary truth. It depends on the power and will of ·God·, the being who made the sun and all the planets and who gave them the motions that seemed best to him.

[Reid remarks that if all truths were necessary, we would need only one tense because everything that was ever true would be always true. He says that for necessary truths we use the present tense, but this is just a convenience. Someone who says ‘two plus two make four’ doesn’t mean to be saying only what the sum of two and two is right now.]

The distinction commonly made between

•abstract truths and •truths that express matters of fact or real existences

coincides to a large extent but not entirely with the distinction between

•necessary truths and •contingent truths.

The necessary truths that we know about are mostly abstract truths, but there is an exception: the truth about the existence and nature of ·God·, the supreme being, which is necessary ·but obviously is a matter of fact and existence·. Other existences are the effects of will and power. They had a beginning and are changeable. Their nature is whatever the supreme being chose to give them. Their attributes and relations must depend on the nature God gave them, the powers he bestowed on them, and the situation in which he placed them.

The conclusions derived by reasoning from first principles will commonly be necessary or contingent depending on whether the principles they are derived from are necessary or contingent. On the one hand, I take it to be certain that whatever can be inferred by valid reasoning from a necessary principle must be itself be a necessary truth, i.e. that no contingent truth can be inferred from principles that are necessary. Thus, because the axioms in mathematics are all necessary truths, so are all the conclusions drawn from them—i.e. the whole of mathematics. But from no mathematical truth can we deduce the existence of anything; not even of mathematical objects.

On the other hand, I think that we can very seldom infer necessary truths from contingent premises. The only example of this I can call to mind is this: from the existence of things that are contingent and changeable we can infer the existence of an unchangeable and eternal cause of them.

The minds of men are occupied much more about contingent truths than about necessary ones, so I shall first try to identify the principles of contingent truths, though I may miss a few. ·I shall present a list of twelve of them, and my discussion of them will occupy the rest of this chapter·.

(1) Everything of which I am conscious really exists.

Consciousness is an operation of the understanding that is like no other, and it can’t be logically defined. [See Reid’s account of ‘logical definition’ in Essay 1, chapter 1 here.] The objects of it are our present pains, our pleasures, our hopes, our fears, our desires, our doubts, our thoughts of every kind—in brief, everything that our minds do or undergo, while it is actually happening. We may remember these doings and undergoings when they are past, but we are conscious of them only while they are present.

When a man is conscious of pain, he is certain of its existence; when he is conscious that he doubts or believes, he is certain of the existence of those operations.

His irresistible conviction of the reality of those operations is immediate and intuitive; it doesn’t come from reasoning. So the existence of the undergoings and doings of our minds of which we are conscious is a first principle that Nature requires us to believe on her authority.

If I am asked to prove that I can’t be deceived by consciousness, to prove that consciousness isn’t a deceptive sense, I can find no proof. I can’t find any antecedent truth from which it is deduced, or on which its evidentness depends. It seems to scorn any such derived authority, and to demand my assent on its own authority.

If someone were so deranged that he denied that he was thinking at a time when he was conscious of thinking, I might wonder or laugh or pity him, but I couldn’t reason with him about this. We would have no common principles from which to reason, so we could never come to grips through argument.

I think this is the only principle of common sense that has never been directly called in question. It seems to be so firmly rooted in men’s minds that it retains its authority with the greatest sceptics. Hume, after annihilating body and mind, time and space, action and causation, and even his own mind, acknowledges the reality of the thoughts, sensations, and passions of which he is conscious.

No philosopher has offered any theory to account for this consciousness of our own thought, and the certain knowledge of their real existence that accompanies it. By this ·theory-silence· they seem to accept that this at least is an original ·or underived· power of the mind, a power by which we have not only •ideas but original •judgments and •knowledge of real existence.

(I can’t reconcile this immediate knowledge of the operations of our own minds with Locke’s theory that all knowledge consists in perceiving the agreement and disagreement of ideas. . . . What are the agreements or disagreements that convince a man that he is in pain when he feels it? Nor can I reconcile it with Hume’s theory that to believe that a thing exists is merely to have a strong and lively conception of it, or anyway that belief is merely some special version of the idea that is the object of the belief. For one thing, the objects of belief are propositions, not ideas. Also, in all the variety of thoughts and other events of which we are conscious, we believe in the existence of the weak as well as of the strong, the faint as well as the lively. No special feature of the operations of our minds inclines us to have any doubt that they really exist.). . . .

But although this principle isn’t supported by any other, a very considerable and important branch of human knowledge is supported by it. Everything we know, indeed everything we can know, about •the structure and powers of our own minds is derived from this source of consciousness; so there is no branch of knowledge that stands on a firmer foundation than •this one does, for surely nothing can be more evident than the deliverances of consciousness.

So how does it come about that in this branch of knowledge—·i.e. knowledge of the structure and powers of our minds·—there are so many conflicting systems? so many controversies that are never resolved? so little that’s fixed and settled? Can it be that philosophers differ most on the topic where they have the surest means of agreement?. . . .

This strange phenomenon can be explained, I think, if we distinguish •consciousness from something that is often wrongly identified with it, namely •reflection.

All men have consciousness at all times, but it on its own can’t give us clear and distinct notions of the operations of which we are conscious, and of their mutual relations and tiny differences. On the other hand, attentive reflection on those operations, making them objects of thought, surveying them attentively and examining them on all sides, is something that very few men perform. The great majority of men never reflect attentively on the operations of their own minds—because they aren’t capable of it or for some other reason. And even for those whom Nature has equipped for it, the habit of reflecting in this way can’t be acquired without much labour and practice.

The only way we can know anything about the immediate objects of sight is through the testimony of our eyes. If we’d had as much difficulty attending to the objects of sight as we have in attentively reflecting on the operations of our minds, our knowledge of visible objects might have been in as backward a state as our knowledge is of the operations of our minds.

But this darkness won’t last for ever. Light will arise on this benighted part of the intellectual globe. When someone has the good fortune to depict the powers of the human mind as they really are in Nature, men who are unprejudiced and reflective will recognise themselves in the picture. And then the only questions will be: How could things that are so obvious be wrapped up in mystery and darkness for so long? How could men be swept away by false theories and conjectures, when they could have found the truth inside themselves if only they had attended to it?

(2) The thoughts of which I am conscious are the thoughts of a being that I call myself, my mind, my person.

The thoughts and feelings of which we are conscious are continually changing, and the present thought is not the thought of a moment ago; but something that I call myself remains through this change of thoughts. This self has the same relation to all the successive thoughts that I am conscious of—they are all my thoughts. And every thought that isn’t mine must be the thought of some other person.

If you ask me for a proof of this, I admit that I can’t give you one; the proposition itself has an evidentness that I can’t resist. Shall I think that thought can stand by itself without a thinking being? or that ideas can feel pleasure or pain? My nature tells me that it is impossible.

And the structure of all languages shows that Nature has dictated the same thing to everyone. For in all languages when men have spoken of thinking, reasoning, willing, loving, hating, they have used personal verbs which from their nature require a person who thinks, reasons, wills, loves, or hates. Evidently men have been taught by Nature to believe that thought requires a thinker, reason requires a reasoner, and love requires a lover.

Here we must part company with Hume, who thinks it is a vulgar error to suppose that in addition to the thoughts we are conscious of there is a mind that has them. If the mind is anything more than impressions and ideas, ·Hume holds·, ‘mind’ must be a word without a meaning. According to him, then, ‘mind’ is a word signifying a bundle of perceptions; or when he defines it more precisely ‘It is that succession of related ideas and impressions of which we have an intimate memory and consciousness’ (Treatise II.i.2). So that is what I am—the succession of related ideas and impressions of which I have the intimate memory and consciousness!

But who is the I that has this memory and consciousness of a succession of ideas and impressions? Oh, it’s nothing but that succession itself!

So I am being taught that this succession of ideas and impressions intimately remembers and is conscious of itself. I would like to be further instructed. Is it that the impressions remember and are conscious of the ideas, or the ideas remember and are conscious of the impressions, or both remember and are conscious of both? Do the ideas ‘remember’ those that come after them as well as those that went before? These questions naturally arise from this system, and they haven’t yet been answered.

But this much is clear: this succession of ideas and impressions not only remembers and is conscious, but also judges, reasons, affirms, denies; indeed it eats and drinks and is sometimes merry and sometimes sad! If it is consistent with common sense to say things like that about a succession of ideas and impressions, what on earth is nonsense?

[Reid then rather laboriously turns a joke that had been used to mock scholastic philosophers into a complex and leaden-footed joke in mockery of Hume. ]

(3) Events that I clearly remember really did happen.

This has one of the surest marks of a first principle: no man ever purported to prove it, yet no man in his right mind questions it. The testimony of memory, like the testimony of consciousness, is immediate; it claims our assent on its own authority.

Suppose that a lawyer, defending a client against the testimony of credible witnesses, were to argue like this:

Admitting that the witnesses are honest, and that they clearly remember the things to which they have testified, it doesn’t follow that the prisoner is guilty. It has never been proved that even the most distinct memory can’t be deceptive. Show me any necessary connection between •the act of the mind that we call ‘memory’ and •the past existence of the remembered event. No-one has ever offered a shadow of argument to prove that they are connected; but this is one link in the chain of proof against the prisoner, and if it is weak the whole proof falls to the ground. Until it is proved that we can safely rely on •the testimony of memory for •the truth about past events, no judge or jury can justly take away the life of a citizen on such doubtful evidence.

We will all agree, I think, that the only effect of this argument on the judge or jury would be to convince them that the lawyer’s judgment had broken down. A defence lawyer is allowed to plead on his client’s behalf everything that is fit to persuade or to move, but I don’t think any defence counsel ever had the nerve to argue in the above fashion. Why not? Surely, because the argument is absurd. Now what is absurd in court is absurd in the philosopher’s chair. Something that would be ridiculous if said to a jury of honest, sensible citizens is equally ridiculous when solemnly said in a philosophical dissertation.

Hume, as far as I remember, hasn’t directly questioned the testimony of memory; but he has laid down the premises for overturning its authority, leaving it to his readers to draw the conclusion.

He works at showing that the belief or assent that always accompanies memory and the senses is nothing but the liveliness of the perceptions they present. He shows very clearly that this liveliness is no reason to believe in the existence of external objects. Obviously, it is no more a reason to believe in the past existence of the objects of memory.

Indeed the theory of ideas that is generally accepted by philosophers destroys all the authority of memory, as well as the authority of the senses. Descartes, Malebranche, and Locke were aware that this theory required them to find arguments to prove the existence of external objects, which the plain man believes on the mere authority of his senses; but those philosophers didn’t realize that this theory made it equally necessary for them to find arguments to prove the existence of past things that we remember.

All the arguments they advanced to support the authority of our senses were very weak and inconclusive, and Berkeley and Hume had no trouble refuting them. It would have been just as easy to refute any argument they could have brought, consistent with •their theory ·of ideas·, to support the authority of memory. ·I shall explain why·.

According to •that theory, the immediate object of memory—as of every other operation of the understanding— is an idea present in the mind. From the present existence of this idea of memory I am left to infer by reasoning that six months or six years ago there did exist something similar to this idea. But what is there in the idea that can lead me to this conclusion? What mark does it bear of the date of its archetype [= ‘the item of which it is a copy’]? Indeed, what evidence do I have that it had an archetype, rather than being the first of its kind?

‘Well, this idea or image in the mind must have had a cause.’ I admit that if there is such an image in the mind, it must have had a cause, and indeed a cause able to produce this effect; but what can we infer from that? Does it follow that the effect is a likeness, a copy, of its cause? If so, it also follows that a picture resembles the painter and a coach resembles the coach maker!

A past event can be known by •reasoning, but that is not •remembering it. When I clearly remember something, I give the back of my hand to reasons for it as well as reasons against it. And so I think does every man in his senses.

(4) Our own personal identity and continued existence extends as far back ·in time· as we remember anything clearly.

We know this immediately, not by reasoning. It seems indeed to be a part of the testimony of memory: everything we remember relates to ourselves in such a way as to imply our existence at the time remembered. Nothing could be more obviously absurd than to suppose that a man might remember what happened before he existed! So, if his memory isn’t deceptive, he must have existed as far back as he remembers anything clearly. This principle is so tightly tied to (3) that one might think they should be coalesced into one. Decide this in whatever way you think fit. The proper notion of identity, and Locke’s views on this subject, have been considered in Essay 4, chapter 6.

(5) Things that we clearly perceive by our senses really exist and really are what we perceive them to be.

All men are led by Nature to put their faith in the clear testimony of their senses, long before they can be biased by prejudices from education or from philosophy. This is too obvious to need proof.

How did we first come to know that our environment contains certain beings whom we call ‘father’ and ‘mother’ and ‘sisters’ and ‘brothers’ and ‘nurse’? Wasn’t it by the testimony of our senses? How did those people get across to us any information or instruction? Wasn’t it by means of our senses?

Obviously, we can’t have any communication, correspondence, or society with any created being except by means of •our senses. Until we rely on •their testimony, we must consider ourselves as being alone in the universe without any other created things, living or inanimate, and be left to converse with our own thoughts.

Berkeley can’t have properly taken in that it is by means of the material world that we have any interactions with thinking beings or any knowledge of their existence, and that by depriving us of the material world he deprived us at the same time of family, friends, country, and every human creature—of every object we could like or admire or care about, except ourselves.

The good bishop surely never intended this. He was too warm a friend, too devoted a patriot, and too good a Christian to be capable of such a thought. He wasn’t aware of the consequences of his system, so we oughtn’t to attribute them to •him; but we must attribute them to •his philosophical system, which stifles every impulse of generosity or neighbourliness.

When I think I am speaking to men who hear me and can judge what I say, I feel the respect that is due to such an audience. I enjoy the two-way traffic of opinions between myself and friends who are open and able, and my soul blesses ·God·, the author of my being, who has enabled me to be entertained in this manly and rational manner.

But Berkeley shows me that this is all a dream, that I don’t see any human face, that all the objects I see and hear and handle are only the ideas in my own mind; ideas are my only companions. Cold company indeed! Every human feeling freezes at the thought!

But, my Lord Bishop, is mine the only mind left in the universe?

‘Oh no. Only the material world is annihilated ·by my philosophy·; everything else remains as it was.’

This apparently offers to comfort me in my forlorn solitude. But do I see those minds? No. Do I see ideas that they have? No. Nor do they see me or my ideas. So they mean no more to me than do the inhabitants of. . . .the moon; and my gloomy solitude returns. Every social tie is broken, and every social affection is stifled.

[Reid goes on to say that Berkeley’s reasoning was fine, and that the trouble lay in his premises. The real culprit is the doctrine that ‘we don’t perceive external objects themselves, but only certain images or ideas in our own minds’. After alluding to his earlier attacks on this, Reid adds:] If external objects are perceived immediately, we have the same reason to believe in their existence as philosophers have to believe in the existence of ideas while they hold them to be the immediate objects of perception.

(6) We have some power over our actions and over the decisions of our will.

All power must be derived from ·God·, the source of power and of every good gift. Its continuance depends on his choosing to let it continue, and it is always subject to his control.

Beings to whom God has given any degree of power, along with understanding to direct their use of it, must be accountable to their maker. But those who are not entrusted with any power aren’t accountable to anyone, for all good conduct consists in the right use of power and all bad conduct in the misuse of it.

To call to account a being who was never entrusted with any degree of power is an absurdity, just as it would be to call to account an inanimate being. So we are sure that if we are in any way answerable to the author of our being, we must have some degree of power that entitles us to his approval when we use it properly, and to his displeasure when we misuse it.

How do we first get the idea of power? It isn’t easy to say. It isn’t an object of sense or of consciousness: we see events succeeding one another, but we don’t see the power by which they are produced. We are conscious of the operations of our minds; but power is not an operation of mind. If our only notions were ones provided by the external senses and by consciousness, it seems impossible that we should ever have any conception of power. That is why Hume, who has reasoned the most precisely on the basis of this •hypothesis—·namely, that all our ideas are copied from impressions·—says that we don’t have any idea of power, and he clearly refutes Locke’s account of the origin of this idea.

But it is futile to reason from a •hypothesis against a fact whose truth everyone can see by attending to his own thoughts. It is obvious that everyone, very early in life, not only has an idea of power but is sure that he has some degree of power in himself. For this belief is necessarily involved in many mental operations that are familiar to everyone and are part of the essential repertoire of a reasonable being. ·I shall cite three operations that essentially involve believing that one has some power·.

(a) It is involved in every act of •volition. ‘Clearly,’ writes Locke, ‘volition is an act of the mind knowingly exerting the control it takes itself to have over any part of the man. . . .’. Thus, every volition implies a belief that one has the power to do the action that is willed. A man may desire to visit the moon, but nothing but insanity could make him will to do so. And if insanity did produce this effect, it would have to be by making him think he did have the power.

(b) This belief is involved in all •deliberation; for no-one in his right mind deliberates about whether to do something that he believes isn’t within his power.

(c) The same belief is involved in any adoption of a planor policy that is reached through deliberation. A man may as well decide to pull the moon off-course as to lift his finger if he believes that it isn’t in his power to do so. The same holds for every promise or contract in which a man gives his word; for anyone who promises something that he doesn’t think he has the power to perform is not an honest man.

Just as these operations involve a belief that one has some power in oneself, so there are others—equally common and familiar—that involve a similar belief about others.

When we give approval or blame to a man for something he has done, or for not doing something he has not done, we must think he had the power to act otherwise. The same is belief is involved in all advice, encouragement, command, and rebuke, and in everything in which we trust someone to do what he has promised. . . .

The belief that there is some degree of power in ourselves and in other people resembles our belief in the existence of a material world in several respects, including this: even those who reject it as a matter of •philosophical theory find themselves having to be governed by it in their •everyday practice. That is what always happens when philosophy contradicts first principles.

(7) The natural faculties by which we distinguish truth from error are not deceptive. If anyone demands a proof of this, it is impossible to satisfy him. Even supposing this principle were mathematically demonstrated, this wouldn’t give the questioner what he wanted, because to judge a demonstration a man must trust his faculties, taking for granted the very thing that is in question. Trying to prove that our reason is not deceptive by any kind of reasoning is absurd in the same way as trying to settle whether a man is honest or not by asking him.

If a sceptic •builds his scepticism on the basis that all our powers of reasoning and judging are deceptive in their nature, or •resolves at least to withhold assent until it is proved that they aren’t deceptive, it is impossible to beat him out of this stronghold by argument, and we’ll have to leave him to enjoy his scepticism.

Descartes certainly made a false step in this matter. He put forward, among other doubts, this one:

However evident things might seem that he received from his consciousness, his senses, his memory, or his reason, perhaps some malignant being had given him those faculties on purpose to lead him astray; and therefore they shouldn’t be trusted without a proper certificate of trustworthiness.

To remove this doubt, Descartes tries to prove the existence of a God who is not a deceiver; from which he concludes that the faculties God had given him are trustworthy.

It is strange that such a sharp reasoner didn’t see that this reasoning obviously involves begging the question. [Reid uses that phrase in its original meaning of ‘trying to support P by an argument in which P lurks among the premises’.] For if our faculties are deceptive, why can’t they deceive us in this reasoning as well as in others? And if they are to be trusted here, without a certificate, why not elsewhere as well?

Every kind of reasoning for the truthfulness of our faculties amounts to no more than taking their own word for it that they are truthful; and that is what we must do, confidently, until God gives us new faculties to sit in judgment on the old ones. Why was Descartes satisfied with such a weak argument for the truthfulness of his faculties? Probably because he never seriously doubted it.

If any truth can be said to be prior to all others in the order of Nature, this one seems to have the best claim; because every time we assent to something that we find evident on the strength of intuition, demonstration, or probabilistic considerations, the truth of our faculties is taken for granted and is, as it were, one of the premises on which our assent is based.

Then how do we come to be assured of this fundamental truth on which all others rest? Well, •evidentness resembles •light in many respects, and one of them may be this: just as

•light, which is the revealer of all visible objects, reveals itself at the same time,

so also, perhaps,

•evidentness, which is the guarantor of all truth, guarantees itself at the same time.

[Reid repeats that it is just a fact about ‘the constitution of the human mind’ that we can’t help assenting to P with a strength corresponding to how evident P is to us. Someone who went against this compulsion would be an intellectually misshapen ‘monster’, like someone born without hands or feet. He compares the sceptic with a man walking on his hands: stop paying attention to him and he will start being sensible and get onto his feet! Then:]

The principle we are considering here, like many other first principles, has a property that is hardly ever possessed by principles that are based solely on reasoning, namely: in most men the principle produces its effect without ever being attended to or thought about. No man ever thinks ‘My natural faculties are not deceptive’ except when he is thinking about the case for scepticism; yet this principle invariably governs his opinions. . . .

Another property of this and many other first principles is that they compel assent •in particular instances more powerfully than •as general propositions. Many sceptics have denied every •general principle of science excepting perhaps the existence of our present thoughts; yet in •particular cases they reason and refute and prove, assent and dissent. They use reasoning to overturn all reasoning, judge that they ought to have no judgment, and see clearly that they are blind!

(8) There is life and thought in our fellow-men with whom we converse.

As soon as children are capable of asking a question or of answering one, as soon as they show signs of love, resentment, or any other feeling, they must be convinced that the people with whom they have these relationships are thinking beings. They are obviously capable of such relationships long before they can reason. Everyone knows that there is a social bond between the nurse and the child before it is a year old. It can at that age understand many things that are said to it.

It can by signs ask and refuse, threaten and beg. It clings to its nurse in danger, shares her grief and joy, is happy in her soothing and caresses and unhappy in her displeasure. I think it must be admitted that these things can’t be so unless the child believes that the nurse is a thinking being.

Well, then, how does a one-year-old child come by this belief? Not by reasoning, surely, because children don’t reason at that age. Nor is it through the external senses, for life and intelligence are not objects of the external senses.

It is hard to determine how or when Nature first gives this information to the infant mind. We can’t find out by remembering our own case, because our memory doesn’t extend that far back. We see it in those who are born blind, and in others who are born deaf; so Nature hasn’t tied it solely to anything visible or audible. When we grow up to the years of reason and reflection, this belief remains. No man thinks of asking himself ‘Why do I think that my friend is a living creature?’. Wouldn’t he be surprised if someone else asked him that absurd question? If he were asked, he might not be able to give any reason that wouldn’t equally be a reason to think that a watch or a puppet is a living creature. But even if you convince him of the weakness of the reasons he gives for his belief, you can’t make him in the least doubtful. This belief stands on a foundation other than that of reasoning. . . .

Setting aside this natural conviction, I think the best reason we can give to show that other men are living and thinking is that their words and actions indicate powers of understanding like those we are conscious of in ourselves. The very same argument, applied ·not to the behaviour of men but· to the works of Nature, leads us to conclude that there is a thinking author of Nature; and it seems just as strong and obvious in that case as in the other. So we may suspect that the mere use of reason can reveal to men •the existence of God as soon as it can reveal that •other men have life and thought. . . .

Our judgments concerning life and thought in other beings are not at first free from error. But the errors children make about this lie on the safe side: they are apt to attribute thought to inanimate things. These errors don’t matter much, and are gradually corrected by experience and mature judgment. But the belief that other men have life and thought is absolutely necessary for us before we are capable of reasoning, which is why the author of our being has given us this belief in advance of all reasoning.

(9) Certain features of the face, tones of voice, and physical gestures indicate certain thoughts and dispositions of mind.

I suppose everyone will admit that many operations of the mind have their natural signs in face, voice, and gesture. [Reid quotes Cicero as saying this. Then:] The only question is this: do we (a) understand the significance of those signs by the constitution of our nature, i.e. by a kind of natural perception similar to sense-perception; or do we rather (b) gradually learn the significance of such signs from experience, as we learn that smoke is a sign of fire and ice a sign of cold? I think (a) is the right answer.

I can’t believe that the notions we have about what is expressed by features, voice, and gesture are entirely the fruit of experience. Children very soon after birth can be frightened and thrown into fits by a threatening or angry tone of voice. I knew a man who could make an infant cry by whistling a sad tune within its hearing, and again by altering his key and melody could make the child leap and dance for joy.

It is not by experience, surely, that we learn what music expresses, for often a piece of music works on us most strongly at our first hearing of it. One tune expresses cheerfulness and festivity, so that when we hear it we can hardly forbear to dance. Another is sorrowful and solemn. One inspires the hearer with tenderness and love; another with rage and fury.

Hear how Timotheus’ varied lays surprise,

And bid alternate passions fall and rise;

While at each change, the son of Lybian Jove

Now burns with glory, and then melts with love.

Now his fierce eyes with sparkling fury glow,

Now sighs steal out, and tears begin to flow.

Persians and Greeks, like turns of Nature, found,

And the world’s victor stood subdu’d by sound.

(from Pope’s Essay on Criticism)

A man can feel these effects without having studied either music or the passions. The most ignorant and uncultivated people to whom Nature has given a good ear feel them as strongly as those who know most.

Face and gesture express things just as strongly and naturally as voice does. The first time someone sees a stern and fierce look, a contracted brow and a menacing posture, he concludes that the person is inflamed with anger. Are we to say that until experience teaches us better we find the most hostile facial expression to be as pleasant as the most gentle and benign? This surely would contradict all experience; for we know that an angry face will frighten a child in the cradle. Who hasn’t noticed that very young children can distinguish, going by tone of voice and facial expression, things said as jokes and things said in earnest? They judge by these natural signs, even when they seem to contradict the artificial signs.

[Reid speaks of our having no memory of first learning how to read faces, voices and gestures, and that we don’t observe children learning this—whereas we do observe them learning that fire burns and knives cut. Then:]

Indeed, I think that it is ·not just empirically unlikely, but downright· impossible that this should be learned from experience. When we •see the sign and •see the thing signified always conjoined with it, experience can teach us how that sign is to be interpreted. But how can experience instruct us when we •see only the sign, and •the thing signified is invisible? That’s what the case is here: the thoughts and passions of the mind, as well as the mind itself, are invisible, so their connection with any sensible sign can’t be first discovered by experience. There must be some earlier source for the knowledge of this connection.

Nature seems to have given men a faculty or sense by which this connection is perceived. And the operation of this sense is closely analogous to that of the external senses.

When I grasp an ivory ball in my hand, I feel a certain sensation of touch. In the sensation there is nothing external, nothing corporeal. The sensation isn’t round or hard; it is an act of feeling of the mind, from which I can’t by reasoning infer the existence of any body. But

by the constitution of my nature the sensation carries along with it the conception of and belief in a round hard body really existing in my hand.

Similarly, when I see the features of an expressive face, I see only various detailed shapes and colours. But

by the constitution of my nature the visible object brings along with it the conception of and belief in a certain passion or sentiment in the mind of the person.

In the former case a sensation of touch is the sign, and the hardness and roundness of the body I grasp is signified by it. In the latter case the facial expression is the sign, and the passion or sentiment is signified by it.

[Reid goes on at some length about the evidence that the significance of facial expressions and gesture is something we know instinctively, i.e. ‘by the constitution of our natures’; he cites the success of well-done pantomimes in communicating thoughts and emotions to people who have had no experience of pantomime. It takes hard work and practice to be a mime, he says, but not to understand a mime’s performance.]

(10) A certain respect should be accorded to human testimony in matters of fact, and even to human authority in matters of opinion.

Before we can reason about testimony or authority, there are many things we need to know, and we can’t know them except on the evidence of testimony and authority. ·God·, the wise author of Nature, has implanted in the human mind a propensity to rely on this evidence before we can give a reason for doing so. This does indeed, in the first period of life, put our judgment almost entirely in the power of those who are close to us; but this is necessary for our survival and for our growing up. If children were so built that they had no respect for testimony or authority, they would—I mean this literally—die for lack of knowledge. They have to •be instructed in many things before they can •discover them by their own judgment, just as they have to •be fed before they can •feed themselves.

But when our faculties mature, we find reason to check the propensity to yield to testimony and authority that was so necessary and so natural when we were very young. We learn to reason about the respect due to them, and see it as a childish weakness to give them more weight than reason justifies. And yet I think that all through life most men are more apt to over-rate testimony and authority than to under-rate them; ·which suggests that· the natural propensity still retains some force ·even when it could be replaced by reasoning·. . . .

(11) For many outcomes that will depend on the will of man, there is a self-evident probability, greater or less according to circumstances.

Some individuals may have such a degree of frenzy and madness that no-one can say what they may or may not do. We have to put such people under restraint, to keep them as far as possible from harming themselves or others. They aren’t regarded as reasonable creatures or as members of society. But with men of sound mind we depend on a certain degree of regularity in their conduct; and we could cite a thousand cases where we could bet ten to one that they will act thus and not so.

If we weren’t confident about how our fellow-men will act in such circumstances, it would be impossible to live in society with them. What makes it possible for men to live in society, and to unite in a political body under government, is that their actions will always be to a large extent governed by the common principles of human nature.

It can always be expected that they will care about their own interest and reputation, and that of their families and friends; that they will resent insults, have some feeling for being obligingly helpful, and have enough regard for truth and justice not to depart from them without temptation.

All political reasoning is based on such principles as these. It is never demonstrative, but it may have a high probability especially when applied to large numbers of men.

(12) In the phenomena of Nature, what happens will probably be like what has happened in similar circumstances.

We must have this conviction as soon as we are able to learn anything from experience, for all experience is based on the belief that the future will be like the past. Take away this principle and the experience of a hundred years makes us no wiser about what is to come.

This is one of the principles that we can confirm by reasoning when we have grown up and observe the course of Nature. We perceive that Nature is governed by fixed laws, and that if it weren’t there could be no such thing as prudence in human conduct: there would be no such thing as a good means to achieving such-and-such an end, because something that did once •lead to that end is just as likely to •block it next time.

But we need the principle before we can discover it by reasoning, which is why it has been built into our constitution and produces its effects before the use of reason.

When we come to the use of reason, this principle remains in full force but we learn to be more cautious in applying it. We observe more carefully the circumstances on which the past outcome depended, and learn to distinguish them from features of the situation that just happened to be there had no effect on the outcome.

To do this—·i.e. to sort out the causally relevant from the irrelevant details·—we often need to perform a number of experiments that vary in their details. Sometimes a single experiment is thought sufficient to establish a general conclusion. For example, when it was once found that at a certain temperature quicksilver became a hard and malleable metal, there was good reason to think that that temperature will always—for ever—produce this effect.

I need hardly mention that the whole structure of natural philosophy is built on this principle, and will collapse into rubble if the principle is taken away.

Therefore the great Newton lays it down as an axiom, or as one of his laws of philosophising, that ‘the causes assigned to natural effects of the same kind must be the same’ [Reid gives it in Latin]. Every man assents to this as soon as he understands it, and no-one asks for a reason for it. So it has the most genuine marks of a first principle.

It is very remarkable that although all our expectation of what will happen in the course of Nature is derived from our belief in this principle, it doesn’t occur to anyone to ask what the grounds are for this belief. I think Hume was the first person to raise this question; and he has shown clearly and conclusively that the belief isn’t •based on reasoning and isn’t •intuitively evident in the way mathematical axioms are. It isn’t a necessary truth.

He has tried to explain it on his own principles. I am not concerned here with examining his account of this universal belief of mankind. Whether or not that account is correct (and I don’t think it is), this belief •is universal among mankind and •is not based on any antecedent reasoning but on the constitution of the mind itself, so you must agree that it is a ‘first principle’ in my sense of that phrase.

Chapter 6: The first principles of necessary truths

There has been no dispute about most of the first principles of necessary truths, so there is less need to dwell on them. It will be sufficient to divide them into different classes, to present some examples of each class, and to make some remarks about the ones whose truth has been called in question.

They may I think most properly be divided according to the sciences to which they belong. ·On that basis they fall into six classes·.

(1) Some first principles could be called ‘grammatical’: every adjective in a sentence must relate to some noun, expressed or understood; every complete sentence must have a verb.

Those who have studied the structure of language, and formed clear notions of the nature and use of the various parts of speech, perceive without reasoning that these principles and others like them are necessarily true.

(2) There are logical axioms: any string of words that doesn’t make a proposition is neither true nor false; every proposition is either true or false; no proposition can be both true and false at the same time; reasoning in a circle proves nothing; whatever can be truly affirmed of a genus can be truly affirmed of all the species and all the individuals belonging to that genus.

(3) Everyone knows that there are mathematical axioms. Ever since Euclid, mathematicians have very wisely laid down the axioms or first principles on the basis of which they reason. And the effect this seems to have had on the stability and progress of this science strongly encourages us to try to lay the foundations of other sciences in a similar manner as far as we can.

Hume thinks he has discovered a weak side even in mathematical axioms; and thinks that it isn’t strictly true, for instance, that two straight lines can’t intersect twice.

The principle he reasons from is that every simple idea is a copy of a preceding impression and therefore can’t be more precise and detailed than that impression. From this he argues:

•No-one ever saw or felt a line that was so straight that it couldn’t cut another equally straight in two or more points.

•Therefore there can be no idea of such a line.

The ideas that are most essential to geometry, such as the ideas of equality of a straight line and a square surface, are, Hume says, far from being clear and determinate, and ·when they are defined· the definitions destroy the demonstrations that geometers put forward. So he finds mathematical demonstration to be a rope of sand.

I agree with this acute author that if we could form no notion of points, lines, and surfaces that were more precise than those we see and handle, there couldn’t be any mathematical demonstration. But everyone who has understanding can construct in his own mind those elegant and precise forms of mathematical lines, surfaces, and solids, doing this by analysing, abstracting, and compounding the raw materials presented to him by his senses

If a man finds that he can’t form a precise and determinate notion of the figure that mathematicians call a ‘cube’, he not only isn’t a mathematician but he can’t become one. But if he does have a precise and determinate notion of that figure, he must perceive that •it is bounded by six perfectly square and perfectly equal mathematical surfaces. He must perceive that •these surfaces are bounded by twelve perfectly straight and perfectly equal mathematical lines, and that •those lines are terminated by eight mathematical points.

When someone is aware of having these conceptions in a clear and determinate form, as every mathematician is, it is useless bring metaphysical arguments to convince him that they aren’t clear. You might as well try to argue a man who is racked with pain that he doesn’t feel any pain.

Every theory that implies that we don’t have precise notions of mathematical lines, surfaces, and solids must be false. So these notions are not copies of our impressions.

The Medici Venus is not a copy of the block of marble from which it was made. The elegant statue was formed out of the rough block, and this was done by a manual operation that could in a literal sense be called ‘abstraction’ [from Latin abstrahere = ‘pull away from’]. Mathematical notions are formed in the understanding, by abstraction of another kind, out of the rough perceptions of our senses.

The truths of natural philosophy are not necessary truths, but contingent ones, because they depend on the will of ·God·, the maker of the world. And so the principles from which they are deduced must also be contingent and therefore don’t belong to this class.

(4) I think there are axioms even in matters of taste. Despite the differences of taste that are found among men, I think there are some common principles even in matters of this kind. I never heard of anyone who thought it a beauty in a human face to lack a nose or an eye, or to have the mouth on one side. In all the centuries that have passed since the days of Homer, there has never been anyone who thought Thersites was beautiful. . . .

Homer and Virgil and Shakespeare and Milton had the same taste; and all men who have known their writings and agree in admiring them must have the same taste. The fundamental rules of poetry and music and painting and dramatic action and eloquence have been always the same and will be so to the end of the world. The variety we find among men in matters of taste is easily accounted for consistently with the views I have been presenting.

There is acquired taste and natural taste. This holds with respect both to the external sense of taste ·using the palate and tongue· and the internal sense of taste ·in judgments of beauty, ugliness etc.·. Habit and fashion have a powerful influence on both.

Some natural tastes can be called rational, while others are merely animal. Children are delighted with brilliant and gaudy colours, with romping and noisy fun, with feats of agility, strength, or cunning; and savages have much the same taste as children. But there are tastes that are more intellectual. It is the dictate of our rational nature that love and admiration are misplaced when there is no intrinsic worth in the object. In rational operations of taste we judge the real worth and excellence of the object, and our love or admiration is guided by that judgment. In such operations there is •judgment as well as •feeling, and the feeling depends on our judgment regarding the object.

Taste that is based on judgment can be brought under principles; I don’t say the same for taste that is acquired ·by habit and fashion· or taste that is merely animal.

The virtues, the graces, the muses, have an intrinsic beauty. It lies not in •the feelings of the spectator but in •the real excellence of the object. If we don’t perceive their beauty, that is because of some defect in us or some twist of our faculties.

And just as there is a •basic ·and intrinsic· beauty in certain moral and intellectual qualities, so there is a •borrowed and derived beauty in the natural signs and expressions of such qualities. The features of the human face, the shaping of the tones of the voice, and the proportions, attitudes, and gestures of the body are all natural expressions of good or bad qualities of the person, and have a beauty or an ugliness that is derived from ·the beauty or ugliness of· the qualities they express.

Works made by human skill may have two sources of derived or non-basic beauty: •some quality of the maker that they express, and •their usefulness, or fitness for the purpose for which they were made.

Some of these things ought to please, others ought to displease. If they don’t, that’s because of some defect in the spectator. Anything that has real excellence will always please people who have a correct judgment and a sound heart.

Here, in summary, is what I have said on this subject: Setting aside the tastes that men acquire through habit and fashion, there is a natural taste that is partly animal and partly rational. All we can say about animal taste is that ·God·, the author of Nature, for wise reasons has built us in such a way that we can

•receive pleasure from contemplating certain objects, and disgust from others, before we are able to

•perceive any real excellence in one or real defect in the other.

But the taste that we can call ‘rational’ is that part of our constitution by which we

•receive pleasure from contemplating what we judge to be excellent in its kind, the pleasure being tied to this judgment and governed by it.

Such rational taste can be true or false, depending on whether the judgment it is based on is true or false. And if it can be true or false, it must have first principles. [Essay 7 of this work is entitled ‘Taste’. It is not offered on the website from which the present text came.]

(5) There are also first principles in morals:

•An unjust action has more demerit than a ·merely· ungenerous one.

•A generous action has more merit than a merely just one.

•No man ought to be blamed for something that he didn’t have the power to prevent.

•We ought not to do to others what we would think unjust or unfair if it were done to us in similar circumstances.

These are moral axioms, and I could cite many more; they seem to me to be just as evident as the axioms of mathematics.

Some people may think this:

Our determinations in matters of taste and of morals ought not to be regarded as necessary truths. They are based on the constitution of •the faculty we call ‘taste’ and •the faculty we call ‘the moral sense’ or ‘conscience’, and these faculties could have been constituted in such a way that their output was different from, even contrary to, what they in fact deliver. We all know that things are sweet or bitter not in themselves but only according to whether they agree or disagree with •the external sense called ‘taste’. Well, similarly, things are beautiful or ugly not in themselves but according to whether they agree or disagree with •the internal sense that we also call ‘taste’; and nothing is morally good or bad in itself, but only according to whether they agree or disagree with •our moral sense.

This theory of morals and taste has been supported in modern times by great authorities. If it is true, it will follow that there can’t be any principles of taste or of morals that are •necessary truths. For according to this system, what we have to say about matters of taste and about morals come down to things like this:

•We are so built that when X is the case we have certain pleasant feelings,

•We are so built that when Y is the case we have certain unpleasant feelings.

And these ·are not necessary, because they· are matters of fact.

But I can’t help having the opposite opinion. I am convinced that a man who held that polite behaviour is very ugly, and that there is great beauty in rudeness and bad manners, would be •judging wrongly, whatever his •feelings were. Similarly, I can’t help thinking that a man who held that there is more moral worth in cruelty, treachery, and injustice than in generosity, justice, prudence, and temperance would be judging wrongly, whatever his constitution was.

And if it’s true that there is judgment in our determinations of taste and of morals, it must be granted that whatever is •true or •false in morals or in matters of taste is •necessarily true or necessarily false. That’s why I have classified the first principles of morals and of taste as necessary truths.

(6) The last class of first principles that I shall mention can be called ‘metaphysical’. I shall mainly attend to three of these that have been called into question by Hume.

The first is this: The qualities we perceive through our senses must have a subject that we call ‘body’, and the thoughts we are conscious of must have a subject that we call ‘mind’.

Shape can’t exist unless there is something that is shaped, and Motion can’t exist without something that is moved— these are as evident as Two and two make four. In perceiving shape and motion I perceive them to be qualities. They have a necessary relation to something in which they exist as their subject. It is only because of the theory of ideas that some philosophers have found it hard to accept this. A subject of the sensible qualities that we perceive through our senses is not an idea either of sensation or of consciousness, so they say that we have no such idea. . . .

The distinction between •sensible qualities and •the substance to which they belong, and between •thought and •the mind that thinks, wasn’t invented by philosophers. It shows up in the structure of all languages, so it must be common to all men who speak with understanding. And I don’t think that any man, however sceptical he may be in theory, can talk for half an hour about the common affairs of life without saying things that imply his belief in the reality of these distinctions.

Locke acknowledges that ‘because we can’t conceive how simple ideas of sensible qualities could exist alone, we think of these qualities as existing in and supported by some common subject’ (Essay II.xxiii.4). Some of his turns of phrase in the Essay seem to leave room for suspicion that this belief that sensible qualities must have a subject is regarded by Locke as a vulgar prejudice rather than a true judgment. But in his first letter to the Bishop of Worcester he clears this matter up, quoting many passages from the Essay to show that he neither denied nor doubted the existence of substances, both thinking and material; and that he believed in their existence on the same grounds that the bishop did, namely that ‘it is inconsistent with our conceptions to suppose that modes and accidents exist by themselves’. He offers no proof of this inconsistency; and I don’t think any proof of it can be given, because it is a first principle.

Locke is to be praised for his precise inquiries into the origin, certainty, and extent of human knowledge. I wish he had turned his attention more particularly to the origin of these two opinions, which he firmly believed: •Sensible qualities must have a subject that we call ‘body’; •Thought must have a subject that we call ‘mind’. These two opinions govern the beliefs of all men, even of sceptics, in the practice of life; and if Locke had properly attended to them he would probably have come to perceive •that sensation and consciousness—·which he wrongly called ‘reflection’·—are not the only sources of human knowledge; •that there are sources of belief in human nature that we can’t explain beyond saying that they necessarily result from the constitution of our faculties; and •that if we threw off their influence on our practice and conduct—if we could!—we would become unable to speak or act like reasonable men.

We can’t give a reason why we believe that our sensations are real and not deceptive, why we believe what we are conscious of, why we trust any of our natural faculties. We say it must be so, it can’t be otherwise. This ·doesn’t give a reason; it· merely expresses a strong belief; but that belief is the voice of Nature, which it is futile to try to resist. But, if in spite of Nature, we try to dig deeper and not trust our faculties unless we find a reason showing that they can’t be deceptive, I’m afraid that in seeking to become wise and to be like gods we shall become foolish, and in our dissatisfaction with the lot of humanity we shall throw off common sense.

The second metaphysical principle I shall discuss is: Anything that begins to exist must have a cause that produced it.

Philosophy is indebted to Hume for, among many other things, calling into question many of the first principles of human knowledge. This put theorisers to work inquiring, more carefully than they had done before, into the nature of the evidence on which those principles rest. Truth can never suffer by a fair enquiry; it can stand being seen naked in good light; and the strictest examination will always, eventually, work to truth’s advantage. Hume was the first, I believe, who ever called into question whether things that begin to exist must have a cause.

There are three lines we can take about this principle: •it is an opinion for which we have no evidence, which men have foolishly taken up without good reason; •it is capable of direct proof by argument; •it is self-evident and doesn’t need proof—it should be accepted as an axiom which reasonable men can’t call into question.

The first of these would put an end to all philosophy, all religion, all reasoning taking us beyond the objects of sense, and all prudence in the conduct of life.

As for the second supposition, namely that this principle can be proved by direct reasoning, I’m afraid we’ll find the proof extremely difficult if not altogether impossible.

I know only of three or four lines of abstract reasoning that philosophers have used to prove that things which begin to exist must have a cause. One is offered by Hobbes, another by Clarke, another by Locke. ·I’m not going to discuss them here·. Hume in his Treatise of Human Nature has examined them all, and in my opinion he has shown that they take for granted the thing to be proved. That kind of false reasoning is something that men are very apt to fall into when they try to prove something that is self-evident.

It has been thought that although this principle can’t be proved through •abstract reasoning, it can be proved from •experience, being validly inferred from instances that fall within our observation. But this method of proof will leave us in great uncertainty, I think, for these three reasons.

(a) The proposition to be proved is not contingent butnecessary. It is not that things that begin to exist usually have a cause or even that they always have a cause; it’s that they must have a cause and can’t begin to exist without one. Propositions of this kind can’t be proved by induction. . . .

That is why no mathematical proposition can be proved by induction. It could found by experience in a thousand cases that the area of a triangle is equal to the rectangle with the same height and half the width, but this wouldn’t prove that it must be so in all cases, which is what the mathematician affirms.

Similarly, even if we had abundant experimental evidence that things that have begun to exist had a cause, this wouldn’t prove that they must have a cause. Experience may show us what the established course of Nature is, but can never show what connections of things are inherently necessary.

(b) General maxims based on experience have only adegree of probability that is proportional to the extent of our experience, and they ought always to be understood as leaving room for exceptions if future experience comes up with any.

The law of gravitation has as much support from experience and induction as any principle can be supposed to have. But if any philosopher shows by clear experiment there is a kind of matter that doesn’t gravitate, the law of gravitation ought to be limited by that exception.

Now, it’s obvious that men have never considered the principle of the necessity of causes as a truth of this kind, one that could be restricted in some way; and that shows that it hasn’t been accepted on the basis of this kind of evidence.

(c) ·Even leaving aside the issue about necessity·, I can’t see that experience could satisfy us that every change in Nature does actually have a cause. For the vast majority of natural events that we observe, the causes are unknown; so we can’t know from experience whether they have causes or not.

Causation is not something we can sense. The only experience we can have of causation at work is in our consciousness of exerting some power when we order our thoughts and actions. This experience is surely too narrow a foundation for the general conclusion that all things that have had or shall have a beginning must have a cause.

For these ·three· reasons, this principle can’t be drawn from experience any more than from abstract reasoning.

·So much for the second supposition, namely that the causal principle can be demonstrated by abstract reasoning or by appeals to experience. Failing that, and failing the first supposition that the principle is rubbish which ought to be jettisoned·, there remains only the third supposition, namely that the causal principle is an underived, basic, self-evident principle. Two reasons can be urged for this.

(a) The universal consent of mankind, not merely of philosophers but also of the great unwashed multitudes.

As far as I know, Hume was the first person who ever expressed any doubt of this principle. And his doubts don’t carry much authoritative weight, given that he has rejected every principle of human knowledge except that of consciousness, not even sparing the axioms of mathematics! Indeed, when it comes to first principles there is no reason why the opinion of a philosopher should have more authority than that of any other sensible person who has been accustomed to judge in such cases. An illiterate plain man is a competent judge, and the philosopher has no privilege in matters of this kind. ·His only relevant difference from the plain man is that· he is more liable than the plain man is to be misled by a favourite theory, especially if it’s his theory!

Setting Hume aside, what philosophy has been busy with ever since men first began to philosophise is the investigation of the causes of things. [Remember that for Reid ‘philosophy’ includes natural science.]. . . . Before Hume it never occurred to anyone to wonder whether things have a cause or not. If anyone had thought that there might be uncaused events, that would surely have come up in the context of the variety of absurd and contradictory causes assigned some events. [Reid recites a couple of the absurdities, then:] We don’t know of any atheistic sect that denied the causal principle, though such a denial would have enabled them to evade every argument that could be brought against them and to answer all the objections to their system. But rather than adopt such an absurdity ·as the denial of the causal principle·, they contrived some imaginary cause for the universe—that it arose from a chance coming-together of atoms, or that it exists because it was necessary for it to exist.

[Reid quotes from Cicero and Plato passages showing their acceptance of the causal principle. He quotes Hume as questioning it, and remarks that what Hume says against it amounts to saying that the principle isn’t intuitively evident because it doesn’t fit Hume’s theory of intuitive certainty. He repeats that ‘the vulgar adhere to this maxim as firmly and universally as the philosophers’. Then:]

This universal belief of mankind is easily accounted for if we allow that the necessity of a cause for every event is obvious to the rational powers of a man. But it is impossible to account for it otherwise. It can’t be ascribed to education, to systems of philosophy, or to priestcraft. You might expect that a philosopher who takes the causal principle to be a general delusion or prejudice would try to show what the causes in human nature are from which such a general error could arise. But in writing that, I was forgetting that Hume might answer, on his own principles, that this error and delusion of men may have occurred right across the species without any cause!

(b) My second reason for holding the causal principle to be a first principle is that men in general don’t just •assent to it as a theoretical matter but •live their lives on the basis of it, applying it to the most important matters. . . .

In large families ·such as mine was·, so many bad things are done by a certain personage called ‘Nobody’ that it is proverbial that every house contains a Nobody who does a great deal of mischief; and even when there is exact inspection and tight parental control, many events will occur that can’t be attributed to anyone but Nobody! So if we trust merely to experience in this matter, Nobody will be found to be a very active person and to have a considerable share in the management of affairs. But however this theory may seem to be supported by experience, it is too offensive to common sense to take in even the most ignorant. A child knows that when his toy is taken away it must have been taken by somebody. . . .

[Reid illustrates the role of the causal principle in human life. Someone who suffers a robbery doesn’t entertain the thought that perhaps his goods disappeared with no cause. A coroner’s jury considers what caused a man’s death; it doesn’t consider that perhaps there was no cause. He comments on what an absurd figure Hume would cut if he intruded into one of those scenes with his challenge to the causal principle; and goes on to say that Hume himself sometimes shows his unconscious acceptance of the principle:] I shall mention only one such passage, in a part of the Treatise of Human Nature where he is engaged in fighting against the causal principle! He writes:

As for the impressions that arise from the senses: in my opinion their ultimate cause is utterly inexplicable by human reason; we will never be able to decide with certainty whether they arise immediately from the object, or are produced by the creative power of the mind, or are caused by God. (Treatise I.iii.5)

Among these alternatives he never thought of their not arising from any cause.

Hume has three arguments purporting to show that the causal principle is not self-evident. (a) All certainty arises from comparing ideas and discovering their unalterable relations; and none of those relations imply Whatever has a beginning must have a cause of existence. I have already examined this theory of certainty.

(b) Whatever we can conceive is possible, ·and we can conceive an uncaused actual event·. I have examined this too.

(c) What we call a ‘cause of x’ is only something thatoccurs before x and is always conjoined with it. This is another of the doctrines that Hume has all to himself; I may have occasion to consider it later. All I shall say here is that this doctrine implies that night is the cause of day and day the cause of night, because no two things have more constantly followed each other since the beginning of the world.

The third and last metaphysical principle I shall discuss—one that is also opposed by Hume—is: If something shows marks or signs of design and intelligence, we can infer with certainty that there was design and intelligence in its cause. ·I shall call this ‘the design principle’. It will be my topic to the end of this chapter·.

Intelligence, design, and skill are not objects of the external senses, and we can’t be conscious of them in anyone but ourselves. Even in ourselves we can’t properly be said to be conscious of our natural or acquired talents; all we are conscious of are the mental operations in which those talents are exerted. Indeed, a man comes to know his own mental abilities just as he knows another man’s, namely by the effects they produce when there is occasion to put them to work.

A man’s wisdom is known to us only by the signs of it in his conduct; his eloquence by the signs of it in his speech. And that is also how we judge someone’s virtue, his fortitude, and all his talents and virtues. But notice this: we judge men’s talents with as little doubt or hesitation as we judge concerning the immediate objects of sense. One person we are sure is a perfect idiot; another who feigns idiocy to screen himself from punishment is found when tested to have the understanding of a man and to be accountable for his conduct. We perceive one man to be open, another cunning; one to be ignorant, another very knowledgeable; one to be slow of understanding, another quick. Everyone forms such judgments regarding those he has any dealings with, and the affairs of everyday life depend on such judgments. . . .

From this it appears that it is just as thoroughly built into us

to judge men’s characters and their intellectual powers on the basis of the signs of them in their actions and talk

as it is

to judge concerning corporeal objects on the basis of our senses.;

that •such judgments are common to every human being who is capable of thinking, and that •they are absolutely necessary in the conduct of life.

Now, every judgment of this kind is just one application of ·the design principle·, the general principle that intelligence, wisdom, and other mental qualities in the cause can be inferred from their marks or signs in the effect. The things men say and do are effects, of which the speakers and doers are the causes. We perceive the effects through our senses, but the causes are behind the scene. We simply infer their existence and their degrees from what we observe in the effects. From wise conduct we infer wisdom in the cause, and so on.

[Reid goes on to remark that people make these inferences with perfect confidence. The design principle’s essentialness for everyday life is another sign of its being a first principle. We don’t get it through reasoning: it is too universal for that to be plausible; and we never find philosophers—even very good arguers—defending it on any other basis than common sense. Reid quotes a long passage in which Cicero constantly deploys the principle—not in arguments but rather in what amount to appeals to common sense. For example:] ‘Carneades imagined that in the stone quarries at Chios he found in a split stone a representation of the head of a little Pan or forest-god. And perhaps he did, but surely not one that you might think had been made by an excellent sculptor; for chance never perfectly imitates design.’ [Reid continues with a very long quotation from Tillotson, of which this is a part:]

I appeal to any man of reason whether anything can be more unreasonable than obstinately to attribute to •chance an effect that carries on the face of it all the signs of •design? Did it ever happen that a considerable work, needing a great variety of parts and an orderly and regular adjustment of them, was done by chance? Will chance fit means to ends in ten thousand instances without failing in any one?. . . . How long might twenty thousand blind men, sent out from the remote parts of England, wander up and down before they would all meet on Salisbury plains and fall into rank and file in the exact order of an army? Yet that is much easier to imagine than how the innumerable blind parts of matter should rendezvous themselves into a world.

[Reid remarks that through the whole long passage Tillotson doesn’t argue for the design principle; he merely exhibits what he thinks are the absurd consequences of denying it, this being an implicit appeal to common sense.]

I have met with one or two respect-worthy authors who appeal to probability theory to show how improbable it is that a regular arrangement of parts should be the effect of chance, or that it should not be the effect of design. I don’t object to this reasoning; but I would point out that probability theory is a branch of mathematics little more than a hundred years old, whereas the conclusion drawn from it—·the design principle·—has been held by all men from the beginning of the world. So it can’t be thought that men have been led to this principle by that reasoning. Also, one may question whether (a) the first principle on which all the mathematics of probability theory is based is more self-evident than (b) this conclusion drawn from it, or whether instead (a) is not a particular instance of (b) that general conclusion.

·So much for the suggestion that we accept the design principle on the strength of abstract reasoning·. Next we should consider whether we might have learned it from experience. . . . I have two reasons for thinking that we can’t have done so.

(a) The principle is a necessary truth, not a contingent one. ·The fact that it squares with our experience doesn’t mean that it can be learned from experience·. Here are two truths that square with the experience of mankind since the beginning of the world:

•The area of a triangle is equal to half the rectangle with the same width and height.

•The sun rises in the east and sets in the west.

So far as experience goes, these truths are on an equal footing. But everyone sees how they differ: one is a necessary truth that can’t possibly be untrue; the other is a contingent truth, depending on the will of ·God·, who made the world. . . . Experience informs us only of what •has been, never of what •must be.

(b) Experience can show a connection between a sign and the thing signified, but only in cases where both the sign and thing signified are perceived, and have always been perceived together. But in a case where only the sign is perceived, experience can’t show its connection with the thing signified. For example: thought is a sign of a thinking thing, a mind. But how do we know that thought can’t occur without a mind? If anyone claims to know this from experience, he is deceiving himself. He can’t possibly have any experience of this, because although we have an immediate knowledge of the existence of thought in ourselves by consciousness, we have no immediate knowledge of a mind. The mind is not an immediate object either of sense or of consciousness. So we are entitled to conclude that the necessary connection between thought and a mind or thinking thing is not learned from experience.

The same reasoning holds for the connection between •a work excellently fitted for some purpose and •design in the author or cause of that work. The work may be an immediate object of perception. But the design and purpose of the author can’t be an immediate object of perception; so experience can never inform us of any connection between the one and the other, let alone a necessary connection.

[Reid repeats that the design principle is a first principle, and then goes on to talk about its importance in ‘natural theology’—i.e. in the branch of theology that infers conclusions about God’s existence and nature from the signs of design in the natural world. Thus:]

The clear marks and signs of wisdom, power, and goodness in the constitution and government of the world constitute an argument for the existence and benevolence of God; and of all such arguments this is the one that has always made the strongest impression on honest and thinking minds. It has a special advantage ·that the others lack·, namely that it gets stronger as human knowledge advances, and is more convincing now than it was a few centuries ago.

King Alphonsus might say that he could devise a better planetary system than the one that the astronomers of his day believed in [he lived in the 13th century]. That system was not the work of God, but a fiction created by men. But since the true system of the sun, moon, and planets has been discovered, no-one, however atheistically inclined, has offered to show how a better one could be contrived.

When we attend to the signs of good design that appear in the works of God, every discovery we make. . . .becomes a hymn of praise to the great creator and governor of the world. Anyone who has the genuine spirit of philosophy will think that it would be impiety—·an insult to God·—to contaminate the divine workmanship by mixing it with those fictions of the human imagination called ‘theories’ and ‘hypotheses’, which will always carry the signs of human folly as much as the other does of divine wisdom.

I don’t know of anyone who ever called into question the ·design· principle as applied to the actions and speech of men. For this would be to deny that we have any means of telling a wise man from an idiot, or an utterly illiterate man from a learned one; and no-one has had the impudence to deny that these differences can be known.

But all through the centuries, people unfriendly to the principles of religion have tried to weaken the force of the argument for the existence and perfections of God that is based on this ·design· principle. That argument has come to be known as ‘the argument from final causes’ [= ‘the argument from purposes’]; and as the meaning of this name is well understood, I shall use it.

The argument from final causes, when expressed as a syllogism, looks like this:

•Design and intelligence in a cause can be inferred with certainty from marks or signs of it in the effect.

•There are in fact the clearest marks of design and wisdom in the works of Nature.

•Therefore the works of Nature are the effects of a wise and thinking cause.

The first premise is the ·design· principle that we have been considering; let us call it the major premise of the argument, and the other the minor premise’. One must either assent to the conclusion or deny one or other of the premises.

[Reid is here using technical terms from the theory of syllogisms. His argument has this form:

All D&I things are caused by W&T things.

Nature is a D&I thing.

Therefore Nature is caused by a W&T thing.

The first premise is the major premise because it contains the predicate of the conclusion; the other is the minor premise. The order in which they are written down is irrelevant.]

Those among the ancients who denied a God seem to me to have conceded the major premise and to have denied the minor, because they didn’t find in the constitution of things clear enough signs of wise design to put the conclusion beyond doubt. . . . The gradual advances in our knowledge of Nature has made this opinion quite untenable.

When the structure of the human body was much less known than it is now, the famous Galen saw such evident marks of wise design in it that, although he had been brought up as an Epicurean, he •renounced that system and •wrote his book The Use of the Parts of the Human Body specifically in order to convince others of what seemed so clear to him, namely that such admirably designed structures couldn’t possibly be the effect of chance. So people who have more recently been dissatisfied with the argument from final causes have left the stronghold of the ancient atheists, which had become untenable, and have chosen instead to defend their position against the major premise.

Descartes seems to have led the way in this, though he was no atheist. He had invented some new arguments for God’s existence, and that may have led him to belittle the arguments that had been used before, so that his own argument would look better. Or perhaps he was objecting to the way the Aristotelians often tried to explain the phenomena of Nature through a mixture of •physical causes and •final causes. [That is, a mixture of •what we would call ‘causes’ and •appeals to a thing’s purpose or ‘end’.] Descartes maintained that only physical causes should be assigned for phenomena, that philosophers ·should· have no use for final causes, and that we are getting above ourselves if we claim to have found out what the purpose was of any work of Nature. [Reid then reports that some Cartesians differed from him on this point, whereas others went the whole way with him. Then:] The most direct attack on the ·design· principle is Hume’s. He puts into the mouth of an Epicurean an argument on which he seems to lay great stress: The universe is a singular effect, so we can’t infer from it any conclusion about whether or not it was made by wisdom. (Treatise I.iv.5)

If I understand the force of this argument, it amounts to this:

If we had been accustomed to seeing ·many· worlds produced, some by wisdom and others without it, and had observed that any world like ours was always an effect of wisdom, then we could have inferred from past experience ·and the facts about our world· that our world was made by wisdom. But we haven’t had any such experience, so we have no way of reaching any conclusion about the causes of our world.

That’s the core of Hume’s argument: If the marks of wisdom seen in one world are not evidence of wisdom ·in the cause·, then similar marks seen in ten thousand ·worlds· won’t give evidence for that either, unless in the past we have perceived •wisdom itself along with the signs or marks of it, and can infer from their perceived conjunction in the past that although in the present world we see only one of the two the other must accompany it—i.e. though we see only •the signs, •the wisdom must accompany them, ·meaning that this world must have been caused by a wise being·.

So we see that Hume’s argument is built on the supposition that we could infer •design from •the strongest marks of it only if we had had experience of always finding these two things conjoined. But I hope I have made it evident that this is not the case—·i.e. that the inference from •the marks of design to •design does not depend on past experience·. Indeed, it is obvious that according to this reasoning we can’t have any evidence of mind or design in any of our fellow-men.

How do I know that some friend of mine has understanding? I never saw his understanding! All I see are certain effects that my judgment leads me to conclude are marks and signs of it. . . .

It seems, then, that the man who maintains that there is no force in the argument from final causes must in consistency think that he has no evidence for the existence of any thinking being other than himself.

Chapter 7: Ancient and modern opinions about first principles

[This sixteen-page chapter focuses mainly on Aristotle, Descartes, and Locke. The main point about Aristotle is that he treated as first principles many propositions that were really ‘vulgar prejudices and rash judgments’, e.g. that Nature abhors a vacuum, that the heavenly bodies move in circles. Descartes, Reid says, went to the other extreme:]

The modern philosophy of which Descartes can fairly be regarded as the founder, though built on the ruins of the Aristotelian philosophy, has a quite opposite spirit that takes it to a contrary extreme. The Aristotelian system adopted as first principles not only •those that mankind have always relied on in their most important transactions but also •many vulgar prejudices; so that this system had a foundation that was broad but in many parts unsound. The modern system has made the foundation so narrow that every superstructure built on it appears top-heavy!

[Descartes, ‘that truly great reformer in philosophy’, was entitled to trust his own consciousness and treat ‘I think’ as a first principle, Reid says, but the case for accepting that is also a case for accepting other principles that Descartes refuses to take on board. He points out that Descartes initially suspended belief even concerning the propositions of mathematics, and adds: ‘And he didn’t allow that there are any necessary truths, maintaining that the truths that are commonly called “necessary” depend on the will of God ·and are therefore contingent·.’ (In sketching the views of some post-Descartes philosophers, Berkeley remarks that the system of Malebranche, with one doctrine deleted from it, is the same as Berkeley’s. He adds: ‘I offer this incidental remark in justice to a foreign author to whom British authors seem not to have given his due.’) Reid’s suggestion about why Descartes was drawn to parsimony in the foundations of his system is noteworthy:]

There is no doubt a beauty in building a large structure of knowledge on a few first principles. The stately edifice of mathematical knowledge, built on the foundation of a few axioms and definitions, charms everyone who sees it. Descartes, who was well acquainted with this beauty in the mathematical sciences, seems to have had the ambition of giving the same beautiful simplicity to his system of philosophy; and therefore sought only one first principle as the foundation of all our knowledge, at least of contingent truths.

[Reid says that Locke was the only Descartes-influenced modern to write explicitly about first principles as such, but he finds Locke’s handling of the topic to be inconsistent. (1) On the one hand, Locke uses first principles as load-bearing parts of his own arguments, for example in his argument in Essay IV.x for the existence of a god:]

If we consider the argument Locke gives for the existence of a first thinking cause, it is obviously based on two principles: •What begins to exist must have a cause of its existence. •An unintelligent and unthinking being can’t be the cause of beings that are thinking and intelligent. With the support of these two principles, he argues very convincingly for the existence of a first thinking cause of things. And if these principles are not true, we can’t have any proof of the existence of a first cause—whether from our own existence or from our experience of other things.

[(2) But on the other hand, Reid continues, Locke equates first principles with ‘maxims’, and under that label he attacks them as true and safe but empty and useless. Reid of course objects to this, not only as inconsistent with Locke’s practice but as wrong in itself. Most of Locke’s discussion of this theme focuses on the maxims

•Whatever exists exists, and

•The whole is larger than a part,

as though these were the only candidates. Locke remarks that Newton in his great work didn’t employ such trivialities as those. Reid replies that the first of them is an identity, and is indeed scientifically useless; and that Newton often used the second of them, because it lies at the heart of geometry. Reid winds up this discussion thus:]

In looking for examples to support his dislike of first principles, Locke couldn’t have made a worse choice than Newton. It was Newton who, by laying down the first principles on the basis of which he reasons in those parts of natural philosophy that he worked on, gave to that science a stability that it never had before, and that it will retain to the end of the world.

[The chapter ends with remarks about the treatment of first principles by other writers, especially Claude Buffier.]

Chapter 8: Prejudices, the cause of error

Our intellectual powers are wisely fitted by ·God·, the author of our nature, for the discovery of as much truth as is suitable for us in our present state. They don’t naturally produce error, any more than the natural structure of the body produces disease. But just as we are liable to various •bodily diseases from accidental causes, external and internal, so also we are from similar causes liable to •wrong judgments.

Medical writers have tried to list the diseases of the body, and to handle them systematically under the name ‘nosology’. If only we had also a ‘nosology’ of the human understanding!

It often happens that we know what is wrong with a body but don’t know how to remedy it; but usually the disorders of the understanding point so plainly to remedies that someone who knows what the trouble is must know the cure for it. Many authors have provided useful materials for this purpose, and some have tried to get them into a systematic form. The general classification that I like best is the one given by Bacon in his fifth book Scientific Advances, and more fully treated in his New Organon. He divides them into four classes:

idols of the tribe

idols of the cave

idols of the market-place

idols of the theatre.

[Reid gives these in Latin.] Perhaps the names are fanciful; but I think that the classification is judicious, like most of the productions of that wonderful genius. And since he invented this classification we can allow him the privilege of naming its classes.

In this chapter I shall explain the headings in this classification, according to Bacon’s own account of what they mean; and I’ll give examples of each, without confining myself to the ones that Bacon gave, and without claiming to have listed them all.

Bacon labels as an ‘idol’ every bias of the understanding by which a man can be misled or drawn into error in judging. The understanding in its natural and best state pays homage only to truth. He regards the causes of error as so many false gods ·or ‘idols’· who receive the homage which is due only to truth.

·IDOLS OF THE TRIBE·

The first class are the idols of the tribe. These are ones that attack the whole human species—·the whole ‘tribe’·—so that everyone is in danger from them. They arise from aspects of the human constitution that are highly useful and necessary for us in our present state, but they can lead us into error through •being taken to extremes or •having some defect or •being steered in the wrong direction.

The sources of action in the human frame are wisely contrived by God for the direction of our •actions, and yet they are apt to lead us astray if they aren’t properly regulated and restrained; and the same thing holds for the parts of our constitution that influence our •opinions. I shall present some examples of this—·six of them, occupying most of the rest of this chapter·.

(1) Men are apt to be led too much by authority in their opinions. In our early years we have no other guide, and we couldn’t learn and develop if we weren’t disposed to accept without question everything we are taught.

When our judgment has matured, there are ·still· many things in regard to which we are incompetent judges. In these matters it is most reasonable to rely on the judgment of those whom we believe to be competent and not selfinterested. The highest court of law in the nation relies on the authority of lawyers and physicians in matters belonging to their respective professions.

Even in matters of which we can have knowledge, authority always will and should have weight—more or less of it depending on •the evidence on which our own judgment is based and on •our opinion of the judgment and honesty of those who disagree with us and those who agree with us. A modest man, conscious of his own fallibility in judging, is in danger of giving too much weight to authority; an arrogant man risks giving too little.

In all matters relating to our knowledge, everyone must go by his own final judgment; otherwise he isn’t behaving like a rational being. Authority may add weight to one side of the scale; but the man holds the balance, and he judges what weight he should allow to authority.

Even confronted by someone claiming to be infallible, we must judge whether he is entitled to that privilege. If someone claims to be an ambassador from heaven, we must judge his credentials. No claim can deprive us of this right, or excuse us for neglecting to exercise it.

So our respect for authority may be too great or too small; the bias of human nature seems to lean towards ‘too great’, and I think it is good for men in general that it should do so.

When this bias is combined with indifference about truth, its operation will be all the more powerful. The love of truth is natural to man, and strong in every well-disposed mind. But it can be overwhelmed by party zeal, by vanity, by the desire to win, or even by laziness. When it is rises above these it is a manly virtue which demands that one work hard and exercise endurance, self-denial, honesty, and preparedness to change one’s mind.

Some people have such a poor and miserable spirit that they would rather owe their survival to the charity of others than to acquire property of their own by working for it; and similarly there are people—many more of them—who could be called mere ‘beggars’ with regard to their opinions. Through laziness and indifference to •truth they leave to others the drudgery of digging for •this commodity; for their purposes they can get enough of it second-hand. What they care about is not knowing what is true but what is said and thought on such subjects; and their understanding, like their clothing, is tailored to suit the current fashion.

This disease of the understanding has taken root so deeply in a great part of mankind that they can hardly be said to use their own judgment at all except in matters that concern their worldly interests. It is not just the ignorant who have the disease; it infects all ·social· ranks. To guess the opinions of people who have it, we need only know where they were born, of what parents, how they were educated, and what company they have kept. These circumstances determine their opinions in religion, in politics, and in philosophy.

(2) A second general prejudice arises from an inclination to think of things that are less well known to us in terms of things that we know better.

This is the foundation of analogical reasoning, which we are naturally inclined to indulge in, ·and not always wrongly·; indeed, we owe a great part of our knowledge to analogical reasoning. It would be absurd to lay it aside altogether, and it is hard to judge how far we may go with it. The bias of human nature is to ·go too far, i.e. to· judge on the basis of analogies that are too slight.

The objects of sense dominate our thoughts in our early years, and all through our lives they’re more familiar to us than anything else. That is why men all down the centuries have been apt to attribute human shape, and human passions and frailties, to superior intelligences and even to ·God·, the supreme being.

Men are inclined to materialize everything (to coin a term), i.e. to apply our notions of material objects to things that are not material. Thought is taken to be analogous to motion in a body. Because

bodies are set in motion by impulses and by impressions made on them by bodies that touch them,

we are inclined to think that

the mind is made to think by impressions that are made on it,

and that

the mind must somehow be in touch with the objects of thought.

And so we get the theories of ideas and impressions that have so generally prevailed.

Because the most perfect products of human skill are •made following a model and •made of materials that already existed, the ancient philosophers all thought that the world was made of a pre-existing uncreated matter; and many of them also thought that there were eternal and uncreated models for every species of things which God made.

Countless mistakes in everyday life come from this prejudice—you can’t have failed to notice them. Men judge other men by themselves or by the small circle of people they know. The selfish man writes off all claims to benevolence and public spirit as mere hypocrisy or self-deceit. The generous and open-hearted man is too vulnerable to sweet talk, and is apt to think men better than they really are. The abandoned and profligate person can hardly be persuaded that there is any such thing as real virtue in the world. The peasant gets his notions of the conduct and characters of men from the ones he experiences in his country village, so he is easily duped when he visits a great city.

It is commonly taken for granted that the only cure for this narrow way of judging men is to have extensive dealings with men of different ·social· ranks, professions, and nations; and that someone who knows only a narrow circle of people is bound to have many prejudices and narrow notions which a wider range of personal contacts would have cured.

(3) Men are often led into error by their love of simplicity, which inclines us to boil things down to a few principles and to think Nature to be much simpler than it really is.

Loving simplicity and being pleased with it wherever we find it—that isn’t an imperfection. On the contrary, it comes from good taste. We can’t help being pleased to see that all the changes of motion produced by the collision of bodies, whether hard, soft, or elastic, are governed by three simple laws of motion which have been discovered through the hard work of philosophers [here = ‘physicists’].

[Reid exclaims at some length over the way Nature presents ‘simplicity of cause and beauty and variety of effects’. Then:] No doubt every work of Nature exhibits all the beautiful simplicity that is consistent with the end for which it was made. But if we hope to discover how Nature brings about its ends merely from the principle that it operates in the simplest and best way, we deceive ourselves and forget that •the wisdom of Nature is further above •the wisdom of man than •man’s wisdom is above •that of a child. [He gives an example of a practical task that a child would get wrong because he doesn’t know enough. Then:]

From fact and observation we can learn something about how Nature operates; but if we conclude that it operates like that only because that appears to our minds to be the best and simplest manner, we shall always go wrong.

[Reid gives a historical example of an error that arose from an undue respect for simplicity, namely the view that all material things are compounded out of the four elements— earth, air, fire, water. Then:]

The Pythagoreans and Platonists were carried further by the same love of simplicity. Pythagoras by his skill in mathematics discovered that there can’t be more than five regular solid [= ‘three-dimensional’] figures bounded by plane surfaces with have the same shape and area. . . . As Nature works in the simplest and most regular way, he thought that all the elementary bodies must have one or other of those ·five· regular shapes; and that the discovery of the properties and relations of the regular solids would be a key to open the mysteries of Nature.

This notion of the Pythagoreans and Platonists undoubtedly has great beauty and simplicity, which is why it prevailed at least up to the time of Euclid. He was a Platonist philosopher, and it is said—and seems to be true—that he wrote the whole of his Elements in order to discover the properties and relations of the five regular solids. . . .

So that this most ancient mathematical work, whose admirable structure has served as a model for all later writers on mathematics, seems to have been intended by its author to exhibit the mathematical principles of natural philosophy—which is also what Newton intended the first two books of his Principia to do.

[Then more examples of simplicity leading scientists into believing things for which there was no real evidence. The handling of physiology in terms of moisture, dryness, heat, and cold. The classification of human body-types into sanguine, melancholy, bilious, and phlegmatic. The belief that all bodies are made up of salt, sulphur, and mercury. The belief that all the objects of thought fall into ten categories, and so on. Then:]

Of all the systems we know, Descartes’s was most remarkable for its simplicity. He builds the whole structure of human knowledge on one proposition, I think. And from mere •matter, together with a certain quantity of •motion given to matter at the outset, he accounts for all the phenomena of the material world. The physical part of this system was sheer hypothesis, with nothing to recommend it but its simplicity; yet it had enough force to end the thousand-year domination of Aristotle’s physics.

Through half a century, the majority of theorists in Europe rejected the principle of gravitation and other attracting and repelling forces, after Newton had given the strongest evidence of their real existence in Nature. They were rejected because they couldn’t be accounted purely in terms of •matter and •motion. That shows how deeply men were in love with the simplicity of Descartes’s system!

Indeed, I think it was this love of simplicity, more than real evidence, that led Newton himself to say about the phenomena of the material world:

Many things lead me to suspect that all phenomena may depend on certain forces by which the particles of bodies are, by causes not yet known, either •impelled toward one another and held together in regular shapes or •repelled from one another and pulled away. (Preface to the Principia)

·I suspect that simplicity is at work here·, because we certainly have no factual evidence that all the phenomena of the material world are produced by attracting or repelling forces. . . .

When a real cause is discovered, the same love of simplicity leads men to credit it with effects that are outside its sphere. It often happens that a medicine, having been found to be of great use for one disease, has its virtues multiplied till it becomes a panacea [= ‘cure for everything’]. . . . In other branches of knowledge the same thing often happens. . . .

(4) One of the richest sources of error in philosophy is the wrong application of our noblest intellectual power to purposes that are beyond its scope.

Of all the intellectual powers of man, that of invention carries the highest price. What it is most like is the power of creation, and sometimes it is honoured by being called just that.

We admire the man who •has a superior talent for finding the means for accomplishing a given end; who •can effectively bring things together so as to produce an effect or make a discovery beyond the reach of other men; who •can draw important conclusions from details that are usually not noticed; who •brings the greatest wisdom to his judgments on the plans of other men and the consequences of his own actions. We label as ‘genius’ this superiority of understanding, and we look up with admiration to everything that carries the signs of it. Yet this power, so valuable in itself and so useful in the conduct of life, can be misapplied; and men of genius in all ages have tended to apply their genius to purposes for which it is altogether incompetent.

The •works of men and the •works of Nature are not of the same order. The force of genius may enable a man perfectly to grasp •the former, and to see the whole way through them. What is designed and carried out by one man can be completely understood by another. On the basis of a part of such a work he can conjecture what the whole is like, or on the basis of its effects he can conjecture what the cause was; and these conjectures can have a high probability, because these works are effects of a wisdom down at his own level.

But the •works of Nature are designed and carried out by a wisdom and power that are infinitely superior to that of ·any· man; and when men try by the force of genius to discover the causes of the phenomena of Nature, all that they get ·from their genius· is a chance of going wrong more ingeniously ·than a less able man would·. Their conjectures may seem very probable to people no wiser than they are, but they have no chance to hit on the truth. They are like a child’s conjectures about how war-ship is built and how it is managed at sea.

Let the man of genius try to •make an animal, even the simplest and lowest kind of animal; or to •make a plant, or even a single leaf of a plant or feather of a bird. He’ll find that all his wisdom and intelligence can’t stand comparison with the wisdom of Nature, or his power with the power of Nature.

The experience of all the ages shows how prone ingenious men have been to invent hypotheses to explain the phenomena of Nature; how eager to ‘discover’ her secrets by guessing at them in advance. Instead of a slow and gradual ascent in the scale of natural causes, by a sound induction from very many particular facts, they want to shorten their task and get straight to the top by a flight of genius. This gratifies the pride of human understanding, but it is an attempt to do something that is beyond us. . . .

When a man has spent all his ingenuity in devising a system, he views it with the eye of a parent; he tugs phenomena around to •make them fit it and •make it look like the work of Nature.

The slow and patient method of induction—the only way to attain any knowledge of Nature’s work—was little understood until it was described by Bacon, and it hasn’t been much followed since his time. It humbles a man’s pride, constantly reminding him that his cleverest conjectures about the works of God are pitiful and childish.

There is no room here for the favourite talent of invention. We must get all our knowledge of Nature by the humble method of reading in the great book of Nature. Anything that isn’t •in that book, or •part of a sound interpretation of it, is the work of man; and the work of God ought not to be contaminated by any mixture with it.

To a man of genius, self-denial is difficult. . . . To bring his fine imaginings and cleverest conjectures to the fiery trial of experiment and induction, by which most if not all of them will be found to be dross, is a humiliating task. This is to condemn him to dig in a mine when he would rather fly with the wings of an eagle.

In all the •fine arts whose purpose is to please, genius is deservedly supreme. In the conduct of •human affairs it often does wonders. But in all •enquiries into the constitution of Nature, genius must play a minor role that doesn’t fit with the superiority it boasts of. It may •combine, but it mustn’t •make. It may •collect evidence, but it mustn’t •make up for the lack of evidence by conjectures. It may display its powers by •putting questions to Nature in well-designed experiments, but it mustn’t •add anything to Nature’s answers.

(5) In avoiding one extreme, men are very apt to rush into the opposite. [Reid illustrates this with the move from primitive animism, which saw gods and demons at work in just about everything, to modern atheism, which doesn’t see gods anywhere. His other example concerns ‘occult qualities’: the Aristotelians brought them in far too much, whereas the Cartesians have gone to the other extreme and ruled them out entirely, making the very label ‘occult quality’ a term of abuse.]

(6) Men’s judgments are often perverted by their affections and emotions. This is so commonly observed and so universally acknowledged that it doesn’t need to be proved or illustrated.

·IDOLS OF THE CAVE·

The second class of idols in Bacon’s classification are the idols of the cave. These are prejudices that arise not from the constitution of human nature but from something special to the individual. Just as objects in a cave vary in their appearance according to the shape of the cave and the way light gets into it, Bacon regards each individual person’s mind as being like a cave that has •its own particular shape and •its own particular way of letting in light; and these two features of the cave often give false colours and a misleading appearance to objects seen in it.

For this reason he labels as ‘idols of the cave’ the prejudices that arise from •the individual man’s training, from •his being a member of some particular profession, or from •some individual quirk of his mind. A man whose thoughts have been kept on track by his profession or manner of life is very apt to judge wrongly when he risks going off that track. He is apt to draw everything into the sphere of •his profession, using •its maxims as a basis for judging things that have nothing to do with it.

The mere mathematician is apt to apply measurement and calculation to things that can’t be measured or calculated. Direct and inverse ratios have been applied by an ingenious author to measure human affections and the moral worth of actions. An eminent mathematician tried to discover by calculation the answer to the question:

By how much per year does the evidential force of facts decrease?

On this basis he purported to fix the time at which •the evidential force of the facts on which Christianity is based will have vanished, so that •no faith will be found on the earth. . . .

I think it was Locke who mentioned an eminent musician who believed that God created the world in six days and rested the seventh because there are only seven notes in music. I knew a musician who thought that there could be only three parts in harmony—bass, tenor, and treble—because there are only three persons in the Trinity! [Reid throws in one more example, involving Henry More. Then:] Thus even very ingenious men are apt to cut a ridiculous figure by pulling onto the track in which their thoughts have long run things that have nothing to do with it. . . .

•Someone—anyone—may, because of his temperament or his upbringing, have particular tendencies in his thinking, and if they are carried to excess they will get in the way of sound judgment. •Some people have too much admiration for antiquity and contempt for anything modern; others go as far into the opposite extreme. . . . •Some are afraid to venture a step off their beaten track, and think it safest to go with the multitude; others are fond of special cases and of everything that has the air of paradox. •Some are slack and changeable in their opinions; others are unduly tenacious. Most men have a liking for the doctrines of their sect or party, and still more for their own inventions.

·IDOLS OF THE MARKET-PLACE·

The idols of the market-place are the fallacies arising from the imperfections and the misuse of language, which is an instrument of thought as well as of the communication of our thoughts. [Bacon gave them that name because a market is a place where men meet and talk to one another.]

No man can pursue a train of thought or reasoning without the use of language. Is this because of our •constitution or rather because of •habits that we have acquired? I shan’t try to answer that. From one or both of •those causes it happens that words are the signs of our thoughts; and the sign is so tightly linked with the thing signified that the thing can hardly present itself to the imagination without drawing the word along with it.

A man who wants to write in some language must think in that language. If he thinks in one language something that he wants to express in another, that will double his work and lead to a final product that will read more like a translation than like an original.

This shows that our thoughts are coloured by the language we use; and that although language ought always to be subservient to thought, thought is sometimes compelled to be subservient to language.

Consider how a servant who is extremely useful and necessary to his master gradually comes to have authority over him, so that the master must often do what the servant wants him to do. Well, language is like such a servant. Its intention is to be a servant to the understanding; but it is so useful and so necessary that we can’t avoid sometimes being led by it, when it ought to follow. We can’t shake off this burden; we have to drag it along with us, and direct our course and regulate our pace as it permits.

Language is bound have many imperfections when it is applied to philosophy, because it wasn’t made for that use. In the early periods of society, rough and ignorant men use certain forms of speech to express their wants, their desires, and their transactions with one another. Their language can’t reach further than their speculations and notions; and if their notions are vague and ill-defined, the words by which they express them must also be vague and ill-defined.

Wilkins had a grand and noble project, namely inventing a philosophical language that would be free from the imperfections of everyday speech. Whether this attempt will ever have enough success to be generally useful I shan’t try to determine, ·but the omens aren’t good·. All the trouble taken by that excellent man in this design have so far produced no effect. Very few people have ever looked closely at all into his views; far less has his philosophical language. . . .been brought into use.

He bases his philosophical language. . . .on a systematic division and subdivision of all the things that may be expressed by language; and instead of the ancient division into •ten categories Wilkins has made •forty categories or highest classes. This classification was made by a very comprehensive mind, but there is room for doubt that it will always suit •the various systems that may be introduced and •all the real growth that may come in human knowledge. The difficulty is still greater when we come to dividing into subclasses. So it is to be feared that this noble attempt of a great genius will prove to be abortive until philosophers have the same opinions and the same systems in the various branches of human knowledge.

There is more reason to hope that the languages used by philosophers may gradually become richer and clearer, and that improvements in knowledge and improvements in language may go hand in hand, and help each other. But I’m afraid that the imperfections of language can never be perfectly remedied while our knowledge is imperfect. [This is one of the places where it is good to remember that for Reid ‘perfect’ can mean ‘complete’.]. . . .

Locke found it necessary to employ one of the four Books of his Essay Concerning Human Understanding to words— their various kinds, their imperfections and misuses and the remedies for both—and his many observations on these subjects are well worth attentive study.

·IDOLS OF THE THEATRE·

The fourth class of prejudices are the idols of the theatre, by which Bacon means prejudices arising from the systems or sects in which we have been trained or which we have adopted. [Bacon wrote: ‘I call them “idols of the theatre” because I regard every one of the accepted systems as the staging and acting out of a fable, presenting its own fictitious staged world.’]

A false theory, once fixed in the mind, becomes (as it were) the medium through which we see objects. They are tinted by it, and seem to have a colour other than the one they have when seen by a pure light. A Platonist, an Aristotelian, and an Epicurean will think differently about a single subject, even when the subject is quite remote from the special doctrines of each of those systems.

A judicious history of the different sects of philosophers, and of the different methods of philosophising that have been followed among mankind, would help men considerably in their search for truth. What would matter most in such a history is not the fine details of each sect’s doctrines, but rather a good account of •the spirit of each sect and of •the point of view from which its founder saw things. Adam Smith in his Theory of the Moral Sentiments perfectly understood this, and applied it to the theories of morals with great judgment and fairness.

Some constitutions of the body make a man more likely to contract one class of diseases than to contract another; and on the other hand when diseases of that kind happen by accident, they are apt to create the bodily constitution that is suited to them. ·I mention this because· there is something analogous to it in the diseases of the understanding.

A certain cast of mind can make a man more likely to accept one system of opinions than another; and, in the other direction, when a system of opinions is fixed in the mind by education or otherwise, it puts the understanding into a condition that is suited to it.

It would be good if the different systems that have held sway could be classified according to their spirit, as well as named after their founders. Bacon distinguished false philosophy into the •sophistical, the •empirical, and the •superstitious, and has made wise observations on each of these kinds. But I think that this subject deserves to be treated more fully by someone like Bacon, if such a person can be found.

Essay 7: Reasoning

Chapter 1: Reasoning in general, and demonstration

Chapter 2: Can morality be demonstrated?

Chapter 3: Probable reasoning

Chapter 4: Hume’s scepticism with regard to reason

Chapter 1: Reasoning in general, and demonstration

The power of reasoning is closely allied to the power of judging, and in everyday life there is no great need to distinguish them precisely—which is why the same name, ‘reason’, is often given to both. The assent we give to a proposition is called ‘judgment’, whether the proposition is self-evident or derives its evidentness from other propositions by reasoning.

Yet reasoning and judging are not the same. Reasoning is the process by which we pass from one judgment to another that follows from it. Accordingly, our judgments are distinguished into •intuitive judgments, which are not based upon any preceding judgment, and •discursive judgments, which are deduced from some preceding judgment by reasoning.

In all reasoning, therefore, there must be •a proposition that is inferred and •one or more from which it is inferred. And this power of ‘inferring’, or ‘drawing a conclusion’, is simply reasoning under another name. The inferred proposition is called ‘the conclusion’ and the propositions from which it is inferred are called ‘the premises’.

Reasoning may consist of many steps, with the first conclusion being a premise for inferring a second conclusion, which in turn serves as a premise for inferring a third, and so on until we come to the last conclusion. Such a many-step process is so easily distinguished from •judgment that it is never called by •that name. But when there is only a single step to the conclusion, the distinction is less obvious and the process is sometimes called ‘judgment’ sometimes ‘reasoning’.

It isn’t surprising that in ordinary speech judgment and reasoning are not very precisely distinguished from one another, because they are sometimes run together even by logicians. We are taught in logic that judgment is expressed by one proposition whereas reasoning requires two or three. But language offers so many different ways of doing things that something that can be expressed by two or three propositions can also be expressed by one. [Remember that Reid often uses ‘proposition’ to mean ‘sentence’—a bit of language rather than something expressed by a bit of language.] For example, I may say

•God is good; therefore good men will be happy.

This is reasoning of that sort that logicians call an ‘enthymeme’ [= ‘argument in which one or more of the premises are left unstated’], consisting of an antecedent proposition and a conclusion drawn from it. But this reasoning can be expressed by a single proposition thus:

Because God is good, men will be happy.

This is what they call a ‘causal proposition’, and therefore it expresses judgment; yet the enthymeme that is reasoning expresses no more.

Reasoning, as well as judgment, must be true or false; both are based on evidentness that may be probable or demonstrative; and both are accompanied by assent or belief.

[The word ‘evidentness’ replaces some of Reid’s uses of ‘evidence’. As well as speaking of

the evidence for proposition P

(using ‘evidence’ in our sense), he will speak of

P’s evidence,

meaning the strength of its candidacy for the label ‘true’, i.e. how evident it is, how much evidentness it has. A self-evident proposition has the highest degree of ‘evidence’ (in this sense), and has it without help from any other proposition; a demonstratively evident proposition may have just as much ‘evidence’, but it gets that from its relation to other propositions. Probabilistic considerations may give a proposition a lower degree of evidence. The clumsy term ‘evidentness’ seems to be the only alternative to following Reid in using ‘evidence’ in two radically different senses.]

The power of reasoning is rightly regarded as one of the special privileges of human nature, because it can lead us—and has led us—to many important truths that would otherwise have been beyond our reach; yet it seems to be only a kind of crutch for a limited understanding. We can conceive of an understanding, superior to what humans have, to which truths that we can only discover by reasoning would appear intuitively—·i.e. wouldn’t need to be reached by reasoning because they would be self-evident·. So although we must ascribe •judgment to God, we don’t ascribe •reasoning to him, because that would imply some defect or limitation of his understanding. And even among men, reasoning one’s way to a conclusion that is self-evident is just fooling around, like a man using crutches when he can walk upon his legs.

What is reasoning? That can be known only by those who •have reasoned and •are capable of reflecting on this operation of their own minds. We can define it only by synonymous words or phrases, such as ‘inferring’, ‘drawing a conclusion’, and the like. The very notion of reasoning, therefore, can enter the mind by only one route—namely, reflecting on the operation of reasoning in our own minds. And such notions as those of

premise

conclusion

syllogism

enthymeme

sorites

demonstration

paralogism

and many others have the same origin.

It is of course Nature that gives us the ability to reason. If someone lacks that ability, he can’t be given it through any kind of therapy or education. But the ability may lie dormant throughout a person’s life, like the seed of a plant that doesn’t ever vegetate because it is too cold and too dry. This is probably the case with some savages.

Although the ability is purely a gift of Nature, and is probably given in very different degrees to different persons, the power of reasoning seems to be acquired by habit as much as the power of walking or running. We can’t recollect our own first exercises of reason, and we can’t clearly identify such first reasonings in others. They’re very feeble, and need to be led by example and supported by authority. The power of reasoning gradually gains strength, chiefly through imitation and exercise.

The exercise of reasoning on various topics not only strengthens the faculty but also provides the mind with a store of materials. Every chain of reasoning that is familiar becomes a beaten track that can lead us to many others. It removes many obstacles that lay in our way, and smoothes many roads that we may want to travel in future inquiries.

If two men whose natural intellectual equipment is the same apply their reasoning power to some subject, the man who has often reasoned on the same subject or on similar ones will do better than one has not, just as a carpenter who has a set of tools for his work will do better than one who still has to make his tools, or even to invent them.

In a chain of reasoning where nothing is left to be supplied by the reader or hearer, the evidentness of each step must be immediately discernible to everyone of mature understanding who has a clear grasp of the premises and the conclusion, and who holds them together in his mind. It is harder, and seems to require a superior natural ability, to take in and hold together in one’s mind a combination of steps of this kind. Anyone can become better at this through practice.

But the highest talent in reasoning is the invention of proofs, by which truths that are ·seemingly· remote from the premises are brought to light. In all works of understanding, invention receives the highest praise; it requires a comprehensive view of what relates to the subject, and alertness in spotting the affinities and relations that may be exploited in a proof.

In all invention there must be some end in view; and skill in finding the road that leads to this end is, I think, what we call ‘invention’ ·or ‘inventiveness’·. I think that the superiority of understanding that we call ‘genius’ chiefly consists in clear and distinct conceptions together with skill in invention. [In Reid’s day ‘genius’ had a less strong meaning than it does today.]

In every chain of reasoning, the evidentness of the final conclusion can’t be greater than that of the weakest link in the chain, however strong the other links are.

The most noteworthy line through reasonings has •probable reasonings on one side of it and •demonstrative reasonings on the other.

In every step of •demonstrative reasoning, the inference is necessary and we see that it is impossible for the conclusion ·of that step· not to follow from the premises. In •probable reasoning, the premises are not connected by necessity to the conclusion, and we don’t see it to be impossible for the premises to be true while the conclusion is false.

So there are no degrees in demonstrative reasoning: one demonstration can’t be stronger than another, though one may be more easily grasped (by minds like ours) than another is. Every demonstration ·from true premises· gives equal strength to the conclusion, leaving no possibility of its being false.

All the ancient philosophers held, I think, that demonstrative reasoning can be applied only to necessary truths, not to contingent ones. I think they were right about this. The existence of all created things is contingent, and so are their attributes and (therefore) the relations resulting from those attributes. Those all depend on the will and power of ·God· who made them. These are matters of fact, which can’t be demonstrated.

What demonstrative reasoning is concerned with, therefore, are the various relations amongst abstract things, i.e. things that we conceive without regard to their existence. Because these are conceived by the mind, and are nothing except what they are conceived to be, we can have a clear and adequate grasp of them. Their relations and attributes are necessary and unchangeable. They are the things that the Pythagoreans and Platonists called ‘ideas’. Let me borrow this meaning of ‘idea’ from those ancient philosophers, and then I have to agree with them that ideas are the only objects about which we can reason demonstratively.

Some of our ideas won’t support any long chain of reasoning. However well defined they are, and however perfectly grasped, ·we can’t reason from them at any length because· their agreements and disagreements are few, and we spot them at once. We may go a step or two in forming a conclusion about such objects, but we can’t go further. There are other ideas about which we can reach very remote and unexpected conclusions through a long chain of demonstrative reasoning.

The reasonings I have met with that can be called strictly demonstrative fall into two classes: •metaphysical and •mathematical.

In metaphysical reasoning the process is always short. The conclusion is a mere step or two—seldom more—from the first principle or axiom on which it is based; and ·though there may be several conclusions that can be drawn from the same axiom·, there is no dependence among these conclusions, ·so they can’t be strung together into a long demonstrative chain·.

It’s not like that with mathematical reasoning. Here the field has no limits. One proposition leads on to another, that to a third, and so on without end.

Why does demonstrative reasoning have such a wide field in mathematics while in other abstract subjects it is held within very narrow limits? I think that this is chiefly because of the nature of quantity, which is the object of mathematics.

Because every quantity has magnitude, and is divisible into parts without end, its magnitude stands in a certain ratio to ·the magnitudes of· every quantity of that same kind. The ratios of quantities are innumerable:

a half

a third

a tenth

double

triple

(Indeed, all the resources of numbers are insufficient to express the variety of ratios, for there are countless ratios that can’t be perfectly expressed by numbers—for example the ratio of the side of a square to its diagonal, the ratio of the circumference of a circle to its diameter.) Every one of this infinity of ratios can be clearly conceived, and clearly expressed, in such a way that there is no risk of one of them being mistaken for another.

Extended quantities such as lines, surfaces, solids, besides the various magnitude-relations they have to one another, also vary just as much in respect of shape; and every mathematical figure ·or shape· can be precisely defined so as to distinguish it from all others.

There is nothing like this with other objects of abstract reasoning. Some of them have various degrees; but they can’t be measured, and can’t be said to have specifiable ratios to others of the same kind. They are either •simple or •compounded out of a few indivisible parts; and so they have (if I may put it this way) only a few points of contact. But mathematical quantities, being made up of countlessly many parts, can be •in contact at countless points and be •compared in countless different ways.

Attempts have been made to measure the merit of an action by the ratio between two of its sources—•affections and feelings, and •principles of action. This may serve in an analogical way to illustrate things that we already knew, but I don’t think that any truth can be discovered in this way. No doubt there are degrees of benevolence, self-love, and other affections, but I don’t think there is any meaningful way of assigning ratios to them.

Some demonstrations are called ‘direct’, others ‘indirect’. The direct ones lead directly to the conclusion to be proved. Some of the indirect ones are so-called ‘demonstrations ad absurdum’. In a demonstration ad absurdum of P, it is demonstrated that not-P is false or leads to an absurdity; from which it follows that P is true. This inference is based on the logical axiom: Of two contradictory propositions, if one is false the other must be true.

Another kind of indirect demonstration proceeds by enumerating all the alternatives to the proposition P and demonstrating that all they are all false. From this it follows that P is true. For example, one line is proved to be equal to another by proving (1) that it can’t be greater and then (2) that it can’t be less; for it must be either •greater or •less or •equal; and when two of these have been knocked out the one left standing must be true. . . .

Chapter 2: Can morality be demonstrated?

What I have said about demonstrative reasoning may help us to judge an opinion that Locke advanced in several places in his Essay, namely that ‘morality is capable of demonstration, as well as mathematics’. In Essay III.xi.15 he remarks that ‘mixed modes’, especially the ones belonging to morality, are combinations of ideas that the mind chooses to put together, and for that reason the meanings of their names can be perfectly and exactly defined. In the next section he writes:

That is why I venture to think that morality is capable of demonstration, as well as mathematics. The precise real essences of the things that moral words stand for can be perfectly known; and so the congruity and incongruity of the things themselves can be certainly discovered, which is to say that there can be perfect knowledge of them. It may be objected that as well as the names of modes the names of substances are often used in morality, and that they will introduce obscurity; but they won’t. When substances are involved in moral discourses, their various natures are not being inquired into but presupposed. For example, when we say that man is subject to law, all we mean by ‘man’ is a corporeal rational creature, with no concern for what the real essence or other qualities of that creature are.

And again:

Here are two ideas that are clear in us: •the idea of a supreme being who made us and •the idea of ourselves. If we thought hard about these and explored them, I think they would provide foundations for our duty and rules of action, in such a way as to make morality one of the sciences capable of demonstration. Relations concerning number and extension are not the only relations between modes that can be perceived with certainty, and I don’t see why the others shouldn’t also be capable of demonstration, if we devised good methods for examining their agreements and disagreements. (Essay IV.iii.18)

He goes on to offer two examples of moral propositions of which we can be as certain as of any in mathematics; and he considers at length what it is about the ideas of quantity that made people think that they are more capable of certainty and demonstration. Later on he writes:

I will say this much: if other ideas that are the real as well as the nominal essences of their species were pursued in the way familiar to mathematicians, they would carry our thoughts further, with results that are more evident and clearer than we are apt to imagine. This gave me the confidence to offer my conjecture (in chapter iii) that not only mathematics but also morality is open to demonstration. (Essay IV.xii.7,8)

From all these passages it appears that this opinion wasn’t a mere passing thought, but something that Locke had turned over in his mind on different occasions. He offers his reasons for it, illustrates it by examples, and considers at length the causes that have led men to think that mathematics is more capable of demonstration than are the principles of morals.

Some of his learned acquaintances, especially his friend Molyneux, urged and nagged him to compose a system of morals according to the idea he had advanced in the Essay; and in answering these requests he only pleads that he has too much else to do, without suggesting any change of his opinion or any great difficulty in doing what was wanted.

The reason Locke gives for this opinion is ingenious; and his regard for virtue—the highest privilege of the human species—made him fond of an opinion that seemed to be favourable to virtue and to have a solid basis in reason.

But we needn’t be afraid that the interests of virtue will suffer from a free and honest examination of this question, or indeed of any question whatever. For the interests of truth will never be in conflict with the interests of virtue. Darkness and error may make friends with vice, but they can never be favourable to virtue.

The philosophers who think that our determinations in morals are not real judgments, that right and wrong in human conduct are only certain feelings or sensations in the person who contemplates the action, must reject Locke’s opinion out of hand. For if the principles of morals are not a matter of •judgment but merely of •feeling, they can’t possibly be demonstrated; and no reason can be given for them except that men are so constituted by ·God·, the author of their being, that they contemplate with pleasure the actions we call ‘virtuous’ and with disgust the ones we call ‘vicious’. . . .

But if our determinations in morality are real judgments, and like all other judgments are either true or false, it is of some importance to understand what kind of basis there is for those judgments.

Here is Locke’s argument for his thesis that morality is capable of demonstration: ‘The precise real essences of the things that moral words stand for can be perfectly known; and so the congruity and incongruity of the things themselves can be certainly discovered, which is to say that there can be perfect knowledge of them.’ (Essay III.xi.16)

It is true that demonstration has to do with the various relations of •things conceived abstractly, of which we can have perfect and adequate conceptions. And Locke, taking all the •things that moral words stand for to be of this kind, concluded that morality is as capable of demonstration as mathematics.

I agree that the names of the virtues and vices, of right and obligation, of liberty and property, stand for abstract things that can be precisely defined, or at least conceived as distinctly and adequately as mathematical quantities. From this it does indeed follow that their mutual relations can be perceived as clearly and certainly as mathematical truths.

Locke gives two relevant examples of this. (1) ‘Where there is no property there is no injustice’, which he calls ‘a proposition as certain as any demonstration in Euclid’ (Essay IV.iii.18). When ‘injustice’ is defined as a violation of property, it is indeed a necessary truth that there can be no injustice where there is no property—it’s as necessary as the truth that you can’t take from a man something that he doesn’t have. (2) ‘No government allows absolute liberty.’ This is just as certain and necessary as the other.

I would call such abstract truths ‘metaphysical’ rather than ‘moral’. We label as ‘mathematical’ all truths that express the relations of quantities, considered abstractly; and all other abstract truths can be called ‘metaphysical’. But if Locke’s two are to be called ‘moral’ truths, then I agree with him that many moral truths are necessarily true and are just as evident as the most evident mathematical truths are.

But something I said earlier should be remembered here: there aren’t many relations among things that are abstractly perceivable by us—except for relations among mathematical quantities—and what few there are can be seen immediately and don’t have to found through a chain of reasoning, a demonstration. They are evident in the manner of mathematical •axioms rather than of mathematical •propositions.

You can see this in Locke’s two examples. (1) follows immediately from the definition of ‘injustice’; (2) follows immediately from the definition of ‘government’. Their evidentness is really intuitive rather than demonstrative; and I think that this, or something close to it, holds for all non-mathematical abstract truths. I gave the reasons for this in chapter 1.

The propositions that I think are properly called ‘moral’ are the ones saying that one or more individual persons have (or don’t have) a certain moral obligation. Locke’s reasoning doesn’t apply to such propositions, because the propositions’ subjects are not things whose real essence can be perfectly known. God made them; their obligation results from the constitution God has given them and the circumstances in which he has placed them. That an individual has such-and-such a constitution and is placed in such-and-such circumstances is not an abstract and necessary truth, but a contingent one. It is a matter of fact, and therefore not capable of demonstrative evidentness, which only necessary truths have.

To each person his own existence is irresistibly evident, but not demonstratively evident. And the same holds for the evidentness to each person that he is a moral agent and under certain moral obligations. Nor is it demonstratively evident—·though it is very evident·—that people other than oneself exist and are endowed with faculties that make them moral and accountable agents.

If man didn’t have the God-given faculty of perceiving certain things in conduct to be right and others to be wrong, and of perceiving his obligation to do what is right and not to do what is wrong, he would not be a moral and accountable being.

If man is endowed with such a faculty, it will enable him to see immediately the rightness of some things and the wrongness of others; so there must be in morals, as in other sciences, first principles that don’t derive their evidentness from any antecedent principles but can be said to be intuitively known.

So moral truths can be divided into two classes—•those that are self-evident to every man whose understanding and moral faculty are mature, and •those that are deduced by reasoning from those that are self-evident. If the •former weren’t known without reasoning, no amount of reasoning could take us to the •latter.

If any man could sincerely say that he isn’t conscious of any obligation

to consult his own present and future happiness,

to keep his promises,

to obey ·God·, his maker, and

to injure no man,

I don’t know what reasoning—whether probable or demonstrative—I could use to convince him of any moral duty. Just as you can’t reason in mathematics with a man who denies the axioms, so also you can’t reason in morals with a man who denies the first principles of morals. The man who doesn’t perceive, by the light of his own mind, some actions to be right and others to be wrong is as incapable of reasoning about morals as a blind man is about colours. If there ever were such a man, he wouldn’t be a moral agent and couldn’t have any moral obligations.

Some first principles of morals must be immediately known, otherwise we have no foundation on which others can rest, no axioms from which we can reason.

Everyone knows for sure that what he approves in other men he ought to do himself in similar circumstances, and that he ought not to do what he condemns other men for doing. Everyone knows that he ought honestly to do the best he can to know what his duty is. To everyone who has a conscience these things are self-evident. They are •immediate dictates of our moral faculty, which is a part of the human constitution; and every man condemns himself, whether he wants to or not, when he knowingly acts contrary to them. So the evidentness of these basic principles of morals—and of others that I could name—appears to me to be •intuitive rather than demonstrative.

The man who acts according to the dictates of his conscience, and takes trouble to learn what his duty is, is a morally perfect man who doesn’t deserve any blame, no matter what errors his understanding may commit. Someone who knowingly acts contrary to the dictates of his conscience is conscious of guilt, and condemns himself. Every particular action that falls evidently within the basic rules of morals is evidently his duty, and it doesn’t take any reasoning to convince him that this is so.

What I think emerges from this is that •everyone of common understanding knows certainly and without reasoning the ultimate ends that he ought to pursue, and that •reasoning is necessary only to discover the best means for attaining them; and with regard to this a good man may indeed often be in doubt.

Thus a law-maker knows that it is his duty to promote •the good of the community, which has entrusted him with authority; and it would be insulting to offer to prove this to him by reasoning. But will •that end be best served by this proposed policy or by that? He may often be in doubt about questions of that sort, and will very rarely find some answer to be demonstratively evident. His •conscience determines what end he ought to pursue, and it is •intuitively evident to him that that end is good; but •prudence has to show him the means for attaining that end—and prudence can almost never use demonstrative reasoning, and must fall back on what appears most probable.

I think that this holds for every kind of duty that we owe to God or man. That is: •the obligation of the most general rules of duty is self-evident; •the application of those rules to particular actions is often equally evident; and •when it isn’t evident but requires reasoning, the reasoning must nearly always be of the probable rather than the demonstrative kind. Sometimes it depends on the temperament and talents and circumstances of the man himself, sometimes on the character and circumstances of others, sometimes on both; and none of these are things that admit of demonstration. . . .

It is commonly and rightly said that the •man of virtue is in a more secure position regarding the achieving of his end than is the •man of the world. This isn’t because he reasons better concerning means to his end (he probably doesn’t), but because mishaps that deeply affect all the concerns of the present world—I mean such things as involuntary errors, unforeseen accidents, and unavoidable ignorance—have no effect on virtue or its reward.

In the common occurrences of life, a man of integrity who has exercised his moral faculty in judging what is right and what is wrong sees his duty without reasoning. . . . The cases that require reasoning are few compared with those that don’t, and a man can be very honest and virtuous without being able to reason and without knowing what ‘demonstration’ means.

The power of reasoning in those who have it can be misused in morals as in other matters. Reasoning will be enormously useful to a man who uses it with an upright heart and an eye focussed on finding what his duty is; but when it is used to justify what a man has a strong ·nonmoral· inclination to do, it will only serve to deceive the man himself and others. When a man can reason, his passions will reason; and they are the most cunning sophists—·the cleverest performers of argumentative trickery·—that we meet with.

If the rules of virtue had to be discovered by demonstrative reasoning, or by reasoning of any kind, that would be a sad thing for the great majority of men, who don’t have the means for developing the power of reasoning. Virtue is the business of all men, and its first principles are written in their hearts in letters so legible that no-one can claim to be ignorant of them or of his obligation to practice them.

Some knowledge of duty and of moral obligation is necessary to all men. Without it they couldn’t be moral and accountable creatures, or capable of being members of civil society. It may therefore be presumed that Nature has put this knowledge within the reach of all men. [Reid continues with this line of thought, stressing the importance of his thesis that moral intuitions are equally available to everyone. Then:]

On the whole I agree with Locke that •propositions expressing the congruities and incongruities of the abstract things that moral words stand for may be as evident as •mathematical truths. But this holds for abstract propositions of every kind, not merely ones that moral words stand for. [Reid gives two examples that are very close to Locke’s two [here], and remarks that it would be better to call them ‘evident’ in the way that mathematical axioms are’ than to say that they are ‘capable of demonstration’. Then:]

Propositions that deserve to be called ‘moral propositions’ are of another kind. They are ones that affirm something to be the duty of persons who really exist. These are not abstract propositions, and so Locke’s reasoning doesn’t apply to them. . . .

Some such propositions are self-evident to everyone who has a conscience, and these are the principles from which all moral reasoning must start. They could be called the ‘axioms’ of morals. But it is very rare for us to be able to reason demonstratively from •these axioms to •any duty that is not self-evident. This does no harm to the cause of virtue, because •acting against •what appears most probable in a matter of duty is as real a trespass against the first principles of morality as •acting against demonstration; and because •someone who has only a little ability at reasoning and makes proper use of it will be accepted ·into heaven· as well as someone to whom God has given ten times as much reasoning ability.

Chapter 3: Probable reasoning

Demonstration’s territory (to repeat myself) is necessary truth; the domain of probable reasoning is contingent truth— not what necessarily must be at all times, but what is or was or will be.

No contingent truth can be strictly demonstrated, but necessary truths can sometimes be merely probable.

Wallis discovered many important mathematical truths by the kind of induction that draws a general conclusion from particular premises. This isn’t strict demonstration, but in some cases it convinces us as completely as demonstration does, and a man can be certain that a truth is demonstrable before anyone has actually demonstrated it. In other cases, induction or analogy can make a mathematical proposition sufficiently probable for a mathematician to be encouraged to look for a way to demonstrate it. Still, the reasoning that is particularly appropriate for mathematical and other necessary truths is •demonstration; and the reasoning that is particularly appropriate for contingent truths is •probable reasoning.

These two kinds of reasoning differ in other respects. In demonstrative reasoning, one argument is as good as a thousand. One demonstration may be more elegant than another, easier to grasp, or more suitable for some further purpose; and any of these may make it preferable to its rivals. But once it has been selected, it is sufficient by itself; it doesn’t need and can’t receive help from any other demonstration. To add more demonstrations of the same conclusion would be a kind of tautology in reasoning. . . .

·In stark contrast with that·, the strength of probable reasoning mostly depends not on any one argument but on many arguments that combine their strengths and lead to the same conclusion. Any one of them by itself would be insufficient to convince; but the whole taken together can have an irresistible force, so that it would be absurd to want something to make their conclusion even more evident. Would anyone ·these days· look for new arguments to prove that there were such persons as Charles I and Oliver Cromwell?

This ·combined-strength· kind of evidentness might be compared to a rope made up of many slender fibres twisted together. The rope is more than strong enough to take the stress that it is subjected to, though no one of its fibres is strong enough for that.

It is often said that it is unreasonable

•to require demonstration for things that don’t admit of it.

It is equally unreasonable

•to require reasoning of any kind for things that are known without reasoning.

All reasoning must start from truths that are known without reasoning. In every branch of real knowledge there must be first principles whose truth is known intuitively, without probable or demonstrative reasoning. They aren’t based on reasoning, but all reasoning is based on them. I have shown that there are first principles of necessary truths and first principles of contingent truths. Demonstrative reasoning is based on the former, and probable reasoning on the latter.

To avoid getting into tangles because of the ambiguity of words, I ought to point out that there is a popular meaning of ‘probable evidentness’, which ought not to be confused with the philosophical meaning that I have explained.

In common language, ‘probable evidentness’ is regarded as a lower degree of evidentness, and is contrasted with certainty: what is certain is more than probable, and what is only probable is not certain. Philosophers regard probable evidentness not as a degree of evidentness but as a kind of evidentness; and it stands in contrast not to certainty but to another kind of evidentness called ‘demonstration’.

Demonstrative evidentness has no degrees; but probable evidentness, taking that phrase it its philosophical sense, has every degree from the very least to the greatest, which we call certainty.

There is such a city as Rome—I’m as certain of that as of anything in Euclid; but its evidentness is not demonstrative but only ‘probable’ (as the philosophers call it). But it would ordinarily sound odd to say ‘It is probable that there is such a city as Rome’, because that implies that one isn’t sure. . . .

In most cases, I think, we measure the degrees of evidentness by the effect they have on a sound understanding when grasped clearly and without prejudice. Every degree of •evidentness that the mind perceives produces a corresponding degree of •assent or •belief. One’s judgment may be in perfect suspense between two conflicting opinions, when neither is evident at all, or when they are equally evident. The least preponderance on one side inclines the judgment in proportion. Belief is mixed with varying amounts of doubt right up to (but not including) the highest degree of evidentness, where all doubt vanishes and the belief is firm and immovable. This degree of evidentness—the highest the human faculties can attain—we call ‘certainty’.

[In the rest of this chapter, most occurrences of Reid’s word ‘evidence’ are left untouched. Up to here he has been writing about evidentness— about a proposition’s candidacy for the label ‘true’—with different degrees of it, ranging from long-shots to shoo-ins. But his next topic is ‘different kinds of probable evidence’, and you’ll see that his topic is not kinds of ‘evidentness’ but rather kinds of basis for a proposition’s having whatever degree of evidentness it does have. And we have a good word for that—it is Reid’s word ‘evidence’!]

There are different kinds of probable evidence. I shall mention the ·seven· main ones, though there may be others.

(1) There is human testimony, on which most human knowledge is built. The credibility of history depends on it, as does the judgment of solemn courts concerning •men’s civil rights and •their guilt or innocence when they are charged with crimes. . . . And no man can act with common prudence in matters that arise in everyday life if he doesn’t have some competence in evaluating human testimony.

Our acceptance of testimony in many cases is not based solely on ·our thinking that· the testifier is a truthful person. In a single testimony, we consider the motives a man might have to falsify. If there seems to be no such motive—and even more if there are motives going the other way—his testimony has weight, independently of his moral character. If the testimony is highly detailed, we consider how well the details square with one another and with things that we know independently. It is very difficult to concoct a story that can’t be detected by a careful examination of the details—so difficult that testimony acquires evidentness by being able to survive such a test. There is an art in detecting false evidence in judicial proceedings, and judges and lawyers know it well; so that I believe few false witnesses leave the bar without anyone suspecting that they have lied.

When many witnesses agree in a great variety of details, without the possibility of their having agreed on a story in advance, the proposition that they testify to may be as evident as if it had been demonstrated.

(2) There is the authority of people who are good judges in the matter in question. The highest law-courts of the British nation often steer by the opinion of lawyers on a point of law, of physicians on a point of medicine, and of other skilled people on matters that relate to their various professions. And in ordinary everyday life we often rely on the judgment of others in matters on which we are not proper judges ourselves.

(3) There is the evidence by which we recognise the identity of things and persons of our acquaintance: It may be abstractly possible that two swords, two horses, or two persons, should be so perfectly alike that they couldn’t be told apart by the people who know them best. But we learn—either from Nature or from experience—that it never happens; or so very rarely that a person or thing we know well is immediately recognised by us, without any doubt, when we perceive the marks or signs that we have been using to distinguish it (·or him or her·) from all other things (·or persons·) of that kind.

We rely on this evidence in the most important affairs of life; and it is by this evidence that the identity of things and of persons is determined in courts of law.

(4) There is the evidence we have regarding men’s future actions and conduct, from the general sources of action in man or from our knowledge of the individuals.

Despite the •folly and •vice that are to be found among men, there’s a certain degree of •prudence and •honesty that we rely upon in everyone who isn’t insane. If this weren’t so, no-one would be safe in the company of anyone else, and men couldn’t form any kind of society. If men were as much disposed to hurt as to do good, to lie as to speak truthfully, they couldn’t live together; they would keep as far as possible from one another, and the human race would soon die out.

We expect that men will take some care of themselves, of their family, friends, and reputation; that they won’t injure others for no reason; that they will have some gratitude for favours and some resentment of injuries.

Such maxims concerning human conduct are the foundation for all political reasoning, and for ordinary prudence in the conduct of life. It isn’t easy for a man to have, in public or in private life, a project that doesn’t depend on the conduct of other men as well as his own, and that doesn’t rely on the supposition that men will do A in circumstances B. This evidence may be probable in a very high degree, but it can’t ever be demonstrative. The best group project may fail, and wise counsels may be frustrated, because some individual acted in a way that couldn’t reasonably have been expected.

(5) A counterpart to that is the evidence that men’s actions, speech, and other external signs provide regarding their characters and plans.

We don’t see men’s hearts or the principles on which they act; but there are external signs of their principles and inclinations; and though these are not certain, we sometimes trust them more than we do what they say. And it is from external signs that we must get all the knowledge we can attain of men’s characters.

(6) There is the evidence that mathematicians call the ‘probability of chances’. We sometimes attribute an outcome O_1 to chance because •we know a remote cause that was bound to produce some one outcome out of the set O_1,. . . ,On but •we don’t know the more immediate cause that settled on O_1 in particular.

I think all the chances that we reason about in mathematics are of this kind. [Reid applies this to the six possible outcomes of the throw of an unbiased die. Then:] Upon such principles as these, the doctrine of chances has provided a very wide field of demonstrative reasoning, although the outcomes that this reasoning focuses on are not necessary but contingent, and not certain but probable.

This may seem to contradict the principle that contingent truths can’t be demonstrated; but it doesn’t. In mathematical reasonings about chance, the conclusion that is demonstrated is not that outcome O will happen, but only that the probability of its happening bears ratio R to the probability of its failing; and this conclusion is necessary, given the suppositions on which it is based.

(7) Finally, there is the evidence by which men have discovered •the known laws of Nature, and the •effects that have been produced by them in former ages or that may be expected in time to come.

The laws of Nature are the rules by which God governs the world. We infer them only from facts that we have observed or that are properly attested by those who have observed them.

Everyone in the course of his ordinary everyday life needs to know some of the laws of Nature. These are soon discovered, even by savages. They know that fire burns, that water drowns, that bodies gravitate towards the earth. They know that day and night, summer and winter, regularly succeed each other. They know that these have happened regularly as far back as their experience and information reach; and this leads them, because of the constitution of human nature, to expect that they will happen in the future in similar circumstances.

The knowledge of the laws of Nature that the philosopher [here = ‘scientist’] gets differs from that of the common man, not in the first principles on which it is based but in its extent and accuracy. He collects with care the phenomena that lead to the same conclusion and compares them with those that seem to contradict or to limit it. He observes the details on which every phenomenon depends, and distinguishes them carefully from the details that are accidentally conjoined with it. He puts natural bodies into various situations, and applies them to one another in various ways, on purpose so as to observe the effect; and in this way he acquires through his senses a more extensive knowledge of the course of Nature in a short time than could be gathered by centuries of casual observation.

But what is the result of his laborious researches? It is that as far as he has been able to observe, W things have always happened in X circumstances, and Y bodies have always been found to have properties Z. These are matters of fact, attested by sense, memory, and testimony, which are also the source of the few facts that the plain man knows.

And what conclusions does the philosopher draw from the facts he has collected? They are that similar events have happened in former times in similar circumstances, and will happen in time to come; and these conclusions have the very same basis as the simple peasant’s belief that the sun will rise tomorrow.

All that we really know of the material world are •facts put into the form of general rules, and •the consequences of those general rules. And the thesis that such general rules have no exceptions, as well as the thesis that they will be the same in the future as in the past, can never be demonstratively evident. It is only evident in the way that philosophers call ‘probable’. General rules may have exceptions or limitations that no-one has happened to observe. The laws of Nature may be changed by God, who established them. But our constitution leads us to rely on their continuance, with as little doubt as if it were demonstrable.

I don’t claim to have listed all the kinds of probable evidence; but those I have mentioned are sufficient to show that by far the greatest and the most interesting part of our knowledge must rest on evidence of this kind; and that many things are certain for which we have only the kind of evidence that philosophers call ‘probable’.

Chapter 4: Hume’s scepticism with regard to reason

In his Treatise of Human Nature I.iv.1 Hume sets out to prove two things: (1) Everything that is called human ‘knowledge’ (meaning demonstrative knowledge) is only probability. (2) When this probability is properly examined, it gradually vanishes until all evidentness is gone. The upshot is that there is no basis for believing any one proposition rather than its contrary, and ‘all those who reason or believe anything are certainly fools’ (I.iv.7).

According to this account, reason—that boasted privilege of man, the light of his mind—is a will-o’-the-wisp which misleads the wandering traveler and eventually leaves him in absolute darkness.

What a miserable condition a man is in if he has a built-in compulsion to •believe contradictions and to •trust a guide—·reason·—who admits to being a false one!

It is some comfort that this doctrine can never be seriously adopted by any man in his senses. After Hume had shown that ‘all the rules of logic require a total extinction of belief and evidentness‘ (I.iv.1), he himself, like all sane men, must have believed many things and given in to the evidentness which he had ·supposedly· extinguished.

He openly admits this. ‘I find myself absolutely and necessarily made to live and talk and act like other people in the common affairs of life. Most fortunately it happens that since reason can’t scatter these clouds, Nature herself suffices for that purpose and cures me of this philosophical gloom and delirium’ [adapted from I.iv.7; all remaining quotations from Hume are from I.iv.1].

This was surely a very kind and friendly thing for Nature to do! For if this philosophical delirium were carried into ·ordinary everyday· life, it would indeed have produced gloomy results.

But what a pity it is that Nature (whoever ‘she’ is), who is so kind as to cure this delirium, should ·first· be so cruel as to cause it! Does the same fountain send forth sweet waters and bitter? Isn’t it more probable that if the cure was the work of •Nature, the disease came from elsewhere and was the work of •the philosopher?

To claim to prove by reasoning that there is no force in reason does indeed look like a philosophical delirium. It is like a man’s claiming to see clearly that he himself and all other men are blind. . . .

Whatever was the cause of this delirium, we must admit that if it were real and not feigned, it couldn’t be cured by reasoning; for if a man disowns the authority of reason, nothing could be more absurd than to try to convince him by reasoning. So it was very fortunate that Nature found other means of curing it.

However, we are entitled to ask this: Was the delirium produced by a soundly applying the rules of logic or rather by misapplying and misusing them? Hume thinks it was the former; others may be apt to think it was the latter.

·Hume’s argument for scepticism about reason has two main parts, which are unsatisfactory in different ways·. First, because we are fallible, Hume concludes that all knowledge degenerates into probability.

We ought to grant that man, and probably every created being, is fallible, and that a fallible being can’t have that perfect grasp and assurance of truth that an infallible being has. It is fitting for a fallible being to be modest, open to new light, and aware that he may be misled by some false bias or by rushing to judgment. Call this a degree of ‘scepticism’, if you like. I can’t help approving of it, being convinced that the man who makes the best use he can of the faculties God has given him, without thinking them more perfect than they really are, may have all the beliefs he needs for his daily life and all he needs to be acceptable to ·God·, his maker.

I grant, then, that human judgments ought always to be formed with a humble sense of our fallibility in judging. That is all that can be inferred by the rules of logic from our being fallible. And if it is all that is meant by our knowledge degenerating into probability, I don’t know of anyone who thinks otherwise.

But I should point out that Hume here uses the word ‘probability’ in a sense for which I know no authority but his own. Philosophers understand probability as opposed to •demonstration; the vulgar understand it as opposed to •certainty; but Hume understands it as opposed to something that no man claims to have, namely •infallibility.

Someone who believes himself to be fallible can still hold it to be certain that two and two make four, and that two contradictory propositions can’t both be true. He can believe some things to be merely probable, and others to be demonstrable, without making any claim to infallibility.

If we use words in their proper meanings, it is impossible that demonstration should degenerate into probability because of the imperfection of our faculties. Our judgment can’t change the nature of the things about which we judge. Something that really is a demonstration will remain so, whatever judgment we form concerning it. Also, when we think that something is a demonstration when really it isn’t, the consequence of this mistake is not that demonstration degenerates into probability, but that what we took to be demonstration is no proof at all; for one false step in a demonstration destroys the whole thing, but can’t turn it into another kind of proof. [Here, as almost everywhere, Reid uses ‘proof’ to stand for something like ‘argument’, with no implication of validity. What he is saying here is that a logically invalid demonstration isn’t a not-very-strong argument; it is no argument.]

I conclude that Hume’s first conclusion, that the fallibility of human judgment turns all knowledge into probability, if understood •literally, is absurd. And if it is only a •figure of speech, and means merely that in all our judgments we ought to remain aware of our fallibility and ought to hold our opinions with the modesty that is fitting for fallible creatures—and I think that this is what Hume meant—then it’s something that nobody denies, and there was no need to enter into a laborious proof of it.

One is never in greater danger of offending against the rules of logic than when trying to prove something that doesn’t need proof. Our present case is an example of this. For Hume begins his proof that all human judgments are fallible by asserting that some are infallible: ‘In all demonstrative sciences the rules are certain and infallible; but when we apply them, our fallible and uncertain faculties are very apt to depart from them and fall into error.’ He must have forgotten that the rules of demonstrative sciences are discovered by our ‘fallible and uncertain’ faculties, and have no authority but that of human judgment! If they are infallible, some human judgments are infallible; and many rules in various branches of human knowledge have as good a claim to infallibility as the rules of the demonstrative sciences.

We have reason here to find fault with Hume •for not being sceptical enough, as well as •for a mistake in reasoning when he claims infallibility for certain decisions of the human faculties in order to prove that all their decisions are fallible!

The second thing that he tries to prove is that this probability, when properly examined, undergoes a continual lessening until eventually it is wiped out altogether.

The obvious consequence of this is that no fallible being can have good reason to believe anything at all. But let us hear the proof:

In every judgment we ought always to correct the •first judgment derived from the nature of the object by a •second judgment derived from the nature of the understanding. Besides •the original uncertainty inherent in the subject, •a second uncertainty arises, derived from the weakness of our judgment ·in arriving at the first probability·. When we have put the two together ·to get a single over-all probability·, we are obliged by our reason to add •a third doubt derived from the possibility of error ·at the second stage· where we estimated the reliability of our faculties. This third doubt is one that immediately occurs to us, and if we want to track our reason closely we can’t get out of giving a decision about it. But even if this decision is favourable to our second judgment, it is itself based only on probability and must weaken still further our first level of confidence. And it must itself be weakened by a •fourth doubt of the same kind, and so on ad infinitum.

Every one of these uncertainties takes away some of the first probability; till at last nothing remains of the first probability; and, however great that was, it must eventually be reduced to zero, by these repeated diminishments. Nothing that is finite can survive an infinity of repeated decreases.

When I reflect on the natural fallibility of my judgment, I have less confidence in my opinions than when I consider only the topic that I am reasoning about; and when I go still further and scrutinize every successive estimation that I make of my faculties, all the rules of logic require a continual lessening and eventually a total extinction of belief and evidentness.

This is Hume’s Achillean argument against the evidentness of reason, from which he concludes that •a man who wants to govern his belief by reason must believe nothing at all and that •belief is an act not of the cogitative but of the sensitive part of our nature. [Reid describes the ancient story about Achilles running a race against an old man, who is given a start. By the time Achilles reaches the old man’s starting-point P_1, the old man has moved on to P_2; by the time Achilles reaches P_2, the old man has moved to P_3, and so on ad infinitum. The spurious conclusion is that Achilles can never catch up with the old man. Then:]

The reasoning of the modern sceptic against reason is equally ingenious, and equally convincing! Indeed they are very similar.

If we trace Achilles’ journey for an appropriate distance, we’ll find the very point where he does overtake the old man. But this short journey is made to appear infinite, by dividing it into an infinite number of stages with corresponding estimations. Similarly, Hume by subjecting every judgment to an infinite number of successive probable estimations, reduces the evidentness to nothing.

To return, then, to the argument of the modern sceptic. I examine the proof of a theorem of Euclid. It appears to me to be a strictly valid demonstration. But I may have overlooked some fallacy; so I examine it again and again, but can find nothing wrong with it. Everyone else who has examined it agrees with me. I have now the evidentness of the truth of the proposition which I and all men call ‘demonstration’, and the belief of it that we call ‘certainty’.

Here my sceptical friend interrupts. and assures me that the rules of logic reduce this demonstration to no evidentness at all. I am willing to hear what step in it he thinks fallacious, and why. He doesn’t object to any part of the demonstration, but pleads my fallibility in judging. I have made the proper allowance for this already, by being open to correction. The conversation continues like this:

My friend: But there are two uncertainties: the •first is inherent in the subject, which I have already shown to have only probable evidentness; the •second arises from the weakness of the judging faculty.

Myself: It is only the weakness of the faculty that reduces this demonstration to what you call ‘probability’. You mustn’t turn it into a second uncertainty; it is the same as the first. To take credit twice for the same article is not agreeable to the rules of logic. So far, then, there is only one uncertainty, namely my fallibility in judging.

My friend: But you are obliged by reason to add a new uncertainty derived from the possibility of error in your estimation of the truth and fidelity of your faculties.

Myself: This estimation ·that you speak of· is ambiguously expressed. It could mean

•an estimation of my liableness to err through the misapplication and misuse of my faculties,

or it could mean

•an estimation of my liableness to err through conceiving my faculties to be true and faithful while they may be false and deceptive in themselves, even when applied in the best manner.

I shall consider this estimation in each of these senses.

[At this point, Reid stops presenting his material in the form of a debate with a friend. He will come to the second resolution of the ambiguity.]

·PERHAPS I MISUSED MY FACULTIES·

If the estimation in question is the first of the two I have listed, then it is true that reason directs us as fallible creatures to carry along with us in all our judgments a sense of our fallibility. It is true also that •how much danger of erring we are in varies from case to case, that •in a given case we may—depending on the details of the case—be able to estimate the danger, and that •we ought also to carry this estimate along with us in every judgment we form.

·What details of the case? Well·, when a demonstration is short and plain, when the point to be proved doesn’t involve our self-interest or our emotions, when the faculty of judging in such cases has grown strong from being much used, there is •less danger of erring; and when the opposite of any of these obtains, there is •more.

In the case now under discussion, every detail is favourable to the judgment I have formed. The danger of going wrong could never be less, except perhaps when I affirm a self-evident axiom.

The sceptic persists, claiming that this decision, though favourable to •my first judgment, must still reduce how evident •it is, because the decision is based merely on probability.

Here I can’t help having a quite contrary opinion, and I can’t imagine how a clever writer could deceive himself so grossly. ·I am sure he deceived himself ·, for surely he didn’t intend to deceive his readers.

After repeated examination of a proposition of Euclid, I judge that:

(1) The proposition has been strictly demonstrated.

Because I am liable to err from various causes, I consider how far I may have been misled by any of these causes in my judgment (1), and about this I judge that:

(2) It is highly unlikely that I went astray in arriving at (1).

To say that because (2) is only probable, it must reduce the evidentness of (1) seems to me contrary to all rules of logic and to common sense.

Compare (1) with the testimony of a credible witness, and (2) with ·the outcome of· an examination of the witness’s character, removing every objection that can be made to it. Surely, (2) must confirm (1) rather than weakening it.

But let us suppose that in another case I examine my first judgment about something, and find that some details of the situation are unfavourable ·to my first judgment’s being right·. What, in reason and according to the rules of logic, ought to be the effect of this discovery?

The effect surely will be, and ought to be, to make me less confident of my first judgment until I re-examine the matter in more favourable circumstances. If it is an important matter, I weigh again the evidentness of my first judgment. If I had rushed to it the first time around, I must now slow down and take every point carefully. If at first I was in a state of high emotion, I must now be cool. If I had an interest in the decision, I must place the interest on the other side. [That sentence is exactly what Reid wrote.]

Despite the suspicious features of the case, it is obvious that my review of the subject may confirm my first judgment. Though the judge was biased or corrupted, it doesn’t follow that the sentence was unjust. Whether the decision was right doesn’t depend on the character of the judge but on the nature of the case—that and nothing else must settle whether the decision was right. The details that made it suspect are mere presumptions, which have no force against direct evidence. [‘Presumption’ was a technical legal term. Example: someone’s not having been heard of for seven years might create a ‘legal presumption’ that he had died, meaning that the courts would take it that he had died unless positive evidence to the contrary turned up.]

Thus, I have considered the effect of this estimate of our liableness to err in our first judgment, allowing it all the effect that reason and the rules of logic permit. In every case where we can’t find any cause of error, ·the outcome of the estimate of our liableness to err· creates a presumption •in favour of the first judgment. In cases where we do uncover a possible source of error, ·the outcome of the estimate of our liableness to err· may create a presumption •against the first judgment. it. But the rules of logic forbid us to judge by presumptions when we have direct evidence. The effect of an unfavourable presumption should only be to make us examine the evidence with the greater care.

The sceptic insists that this estimation must be subjected to another estimation, that to a third, and so on ad infinitum; and as every new estimation reduces somewhat •the evidentness of the first judgment, •it must eventually be totally annihilated. ·I have three things to say about this·.

(1) I have shown that the first estimation, supposing it to be unfavourable, can afford only a presumption against the first judgment; the second, supposing it to be unfavourable, will be only the presumption of a presumption. . . . and so on. This infinite series of presumptions resembles an infinite series of quantities decreasing in geometrical proportion, which amounts only to a finite sum—·as the sum of the infinite series of fractions ½, ¼,. . . has a sum = 1·. The infinite series of stages of Achilles’s journey following the old man amounts to only two thousand paces; and this infinite series of presumptions, even if they are all unfavourable to the first judgment, ·also has a finite sum·: the totality of them can’t outweigh one solid argument in favour of the first judgment.

(2) I have shown that the estimation of our first judgment may strengthen it; and the same thing may be said of each subsequent estimation. So it would be as reasonable to conclude that the first judgment will be brought to •infallible certainty when the series of estimations is wholly in its favour as to conclude its evidentness will be brought to •nothing by such a series if they are wholly unfavourable to it! But in reality one serious and cool re-examination of the evidence by which our first judgment is supported has and ought to have more force to strengthen or weaken the first judgment than an infinite series of estimations of the sort that Hume requires.

(3) I know no reason, and no rule in logic, that requires that such a series of estimations should be conducted after every particular judgment.

A wise man who has done a great deal of reasoning knows that he is fallible, and carries this conviction along with him in every judgment he makes. He also knows that he is more liable to err in some cases than in others. He has a scale in his mind by which he estimates his liableness to err, and he adjusts how strongly he assents to his first judgment to where the case stands on that scale.

Hume’s reasoning supposes that when a man forms his first judgment he thinks of himself as infallible; that by a second and subsequent judgment he discovers that he is not infallible; and that by a third judgment subsequent to the second he estimates his liableness to err in such a case as the present.

If the man does go about things in this way, I agree that his second judgment will with good reason bring down the first from supposed infallibility to fallibility; and that his third judgment will in some degree either strengthen or weaken the first as adjusted in the light of the second.

But every intelligent man goes about things in the opposite way. When about to judge concerning some particular point, he knows already that he isn’t infallible. He knows which are the cases in which he is most or least liable to err. The conviction of these things is always present to his mind, and it influences the strength of his assent in his first judgment, influencing it as much as seems to him reasonable.

If he should later find reason to suspect his first judgment, and wants to have all the satisfaction his faculties can give, reason will direct him not to form a series of estimations upon estimations such as Hume requires, but rather to examine the evidentness of his first judgment carefully and coolly; and this review may, according to its result, either strengthen or weaken or totally overturn his first judgment.

So this infinite series of estimations is not the method that reason directs us to follow in arriving at a judgment in any case. It is introduced without necessity, without any use except to puzzle the understanding and make us think that judging even in the simplest and plainest cases is a matter of insurmountable difficulty and endless labour; just as the ancient sceptic made a journey of two thousand paces appear endless by dividing it into an infinite number of stages.

·PERHAPS MY FACULTY OF JUDGMENT IS DEFECTIVE·

I remarked [here] that the estimation that Hume requires can be understood in another way—one that •better fits his ·and my friend’s· phrase ‘the possibility of error in your estimation of the truth and fidelity of your faculties’, but •is inconsistent with what he has said earlier.

By the ‘possibility of error in the estimation of the truth and trustworthiness of our faculties’ one could be referring to the possibility that we may err by trusting our faculties to be true and faithful when they may be false and deceptive even if used according to the rules of reason and logic.

If this is Hume’s meaning, I answer first that the truth and trustworthiness of our faculty of judging is and must be taken for granted in every judgment and in every estimation.

If the sceptic can seriously doubt the truth and trustworthiness of his faculty of judging when it is properly used, and suspend his judgment about that until he finds proof, his scepticism can’t be cured by reasoning, and he must stay with it until he is given new faculties that are authorized to sit in judgment on the old! And there’s no need for an endless succession of doubts on this subject, for the very first one puts an end to all judgment and reasoning, and to the possibility of convincing him by that means. The sceptic has here established himself in a stronghold that is impregnable to •reasoning, and we must leave him in possession of it until Nature by some •other means makes him give it up.

Secondly, I note that this way of basing scepticism on the supposedly untrustworthy nature of our faculties contradicts what Hume said earlier in this very same argument, namely that ‘The rules of the demonstrative sciences are certain and infallible’, and that ‘Truth is the natural effect of reason ,and error arises from the intrusion of other causes’.

But perhaps he made these concessions carelessly. If so, then he is free to retract them and to base his scepticism solely upon this: No reasoning can prove the truth and trustworthiness of our faculties. Here he stands on firm ground. . . .

All that I ask of this kind of sceptic is that he be uniform and consistent, and that his practice in life not belie his announced scepticism concerning the trustworthiness of his faculties: For just as •faith is best shown by works, so also is •lack of faith! If a sceptic avoids the fire as much as those who believe that entering it would be dangerous, we can hardly avoid thinking his scepticism to be pretended and not real.

Hume indeed was aware that neither his scepticism nor that of any other person could endure this trial, and therefore he covers himself against this point. He writes:

Neither I nor anyone else was ever sincerely and constantly of that ·sceptical· opinion. Nature, by an absolute and uncontrollable necessity, makes us judge as well as breathe and feel. . . . Then why did I display so carefully the arguments of that fantastic sect (·the total sceptics·)? It was to make you aware of the truth of my hypotheses that •all our reasonings about causes and effects are derived from nothing but custom, and that •belief is strictly an act of the sensitive part of our natures rather than of the cogitative part.

I have already considered the first part of this hypothesis, namely that our reasoning about causes is derived only from custom. [This presumably refers to Essay 1 in Reid’s Essays on the Active Powers of Man.]

The other part of Hume’s hypothesis here mentioned is obscurely expressed, though he seems to have thought about how to put it, because it is in italics. Surely it can’t mean that belief is not an act of thinking. So what he is calling ‘the cogitative part of our nature’ isn’t •the power of thinking. And it can’t be •the power of judging, because all belief implies judgment—believing a proposition is the same thing as judging it to be true. So it is presumably •the power of reasoning that he calls ‘the cogitative part of our nature’.

If that’s his meaning, I agree with it in part. The belief in first principles is not an act of our reasoning power, for all reasoning must be based on such principles. We judge them to be true and believe them without reasoning. But I don’t understand why this power of judging of first principles should be called the ‘sensitive part of our nature’.

As our belief in first principles is an act of pure judgment, without reasoning, so also our belief in the conclusions drawn by reasoning from first principles may, I think, be called ‘an act of the reasoning faculty’.

Summing up this chapter: I see only two conclusions that can be fairly drawn from this deep and intricate reasoning against reason. (1) We are fallible in all our judgments and in all our reasonings. (2) The truth and trustworthiness of our faculties can never be proved by reasoning; and therefore our belief in it can’t be based on reasoning. If (2) is what Hume is calling his ‘hypothesis’, I accept it (and think that it isn’t an hypothesis but an obvious truth); though I think it to be very poorly expressed by saying that belief is strictly an act of the sensitive rather than of the cogitative part of our nature.