G. E. MOORE, Litt.D.

Hon. LL.D. (St. Andrews), F.B.A.

Lecturer in Moral Science in the University of Cambridge Author of "Principia Ethica"

LONDON

ROUTLEDGE & KEGAN PAUL LTD

BROADWAY HOUSE: 68-74 CARTER LANE, E.C.4

1922

CONTENTS

I.THE REFUTATION OF IDEALISM 1

II.THE NATURE AND REALITY OF OBJECTS OF PERCEPTION 31

III.WILLIAM JAMES' "PRAGMATISM"97

IV.HUME'S PHILOSOPHY147

V.THE STATUS OF SENSE-DATA168

VI.THE CONCEPTION OF REALITY197

VII.SOME JUDGMENTS OF PERCEPTION220

VIII.THE CONCEPTION OF INTRINSIC VALUE253

IX.EXTERNAL AND INTERNAL RELATIONS276

X.THE NATURE OF MORAL PHILOSOPHY310

Those of the papers in this volume, which have been previously published, originally appeared as follows:—

I. "The Refutation of Idealism" in Mind, N.S. Vol. xii, 1903.

II. "The Nature and Reality of Objects of Perception" in Proceedings of the Aristotelian Society, 1905-6.

III. "Professor James' 'Pragmatism'" in Proceedings of the Aristotelian Society, 1907-8.

IV. "Hume's Philosophy" in The New Quarterly, November, 1909.

V. "The Status of Sense-Data" in Proceedings of the Aristotelian Society, 1913-14.

VI. "The Conception of Reality" in Proceedings of the Aristotelian Society, 1917-18.

VII. "Some Judgments of Perception" in Proceedings of the Aristotelian Society, 1918-19.

IX. "External and Internal Relations" in Proceedings of the Aristotelian Society, 1919-20.

PREFACE

All the papers contained in this volume, except the two ethical ones (VIII and X), have been previously published; and of those which have been previously published all, except that on "External and Internal Relations" (IX), are here re-printed without change. They were written at various dates between 1903 and 1921, and all are here printed in the order in which they were written, except that VIII on "The Conception of Intrinsic Value," which was written earlier than VI and VII, has been moved out of its proper place in order to bring it nearer to IX and X, to both of which it is closely related in subject.

All, except IV and X, were primarily intended for an audience familiar with the writings of philosophers; but I hope that they may nevertheless prove intelligible even to those who have read little or no philosophy, since I make little use of technical terms, and, where I have done so, have done my best to explain in ordinary language exactly what I mean by them. The tone of X is somewhat different from that of the rest, because it was written as a lecture for the Leicester Philosophical Society, with regard to which I was informed that I must not assume any previous acquaintance with philosophy in most of the audience. It accordingly bears marks throughout of the kind of audience for which it was intended.

An attentive reader will easily discover that some of the views expressed in some of the papers are inconsistent with views expressed in others. The fact is that some of the views expressed in some of the earlier ones are views with which I no longer agree; and I feel that some apology is needed for nevertheless republishing them exactly as they stood. In all cases, except one, my excuse is that the mistaken views in question are so embedded in the form and substance of the papers in which they occur, that it would have been impossible to correct them without practically substituting new papers for the old ones; and that, in spite of these mistakes, the old papers, as they stand, still seem to me, on the whole, to say things which are worth saying in a form which, however defective it may be, I doubt my own ability to improve upon. The only case in which I doubt whether this excuse applies is that of the first paper—"The Refutation of Idealism." This paper now appears to me to be very confused, as well as to embody a good many down-right mistakes; so I am doubtful whether I ought to have included it. But in this case I have another excuse: namely that it is a paper to which a good many allusions have been made by contemporary writers on philosophy; and I was told that, for some readers at all events, it would be a convenience that it should be re-printed along with the rest, if only for the sake of reference.

I said above that the only one of the previously published papers, in which changes have been made, is IX on "External and Internal Relations." In this case the changes are not due to any change in my views, but to the fact that, in that part of the paper in which symbols are used, I tried, when it was first published in the Proceedings of the Aristotelian Society, to use the symbols adopted by Whitehead and Russell in Principia Mathematica, and used them also without giving an explanation of their meaning which would be sufficient for readers not acquainted with that work. The symbols in question are symbols which it is difficult for printers to reproduce; and I have, therefore, thought it better, on this occasion, to use another set of symbols, which seem to me to be adequate for the limited purpose I had in view. I have tried to give an explanation of their meaning, which will enable anyone to understand them; and I have taken the opportunity of rewriting some of the parts of the paper in which they occur in a way which will, I hope, make some points clearer than they originally were.

I have to thank the Committee of the Aristotelian Society for permission to reprint the large number of papers (viz., II, III, V, VI, VII and IX), which originally appeared in the Proceedings of that Society; and the Editor of the New Quarterly for permission to reprint the article on Hume's Philosophy (IV), which appeared in that Journal in November, 1909.

G. E. MOORE.

CAMBRIDGE, January, 1922.

Philosophical Studies

THE REFUTATION OF IDEALISM

Modern Idealism, if it asserts any general conclusion about the universe at all, asserts that it is spiritual. There are two points about this assertion to which I wish to call attention. These points are that, whatever be its exact meaning, it is certainly meant to assert (1) that the universe is very different indeed from what it seems, and (2) that it has quite a large number of properties which it does not seem to have. Chairs and tables and mountains seem to be very different from us; but, when the whole universe is declared to be spiritual, it is certainly meant to assert that they are far more like us than we think. The idealist means to assert that they are in some sense neither lifeless nor unconscious, as they certainly seem to be; and I do not think his language is so grossly deceptive, but that we may assume him to believe that they really are very different indeed from what they seem. And secondly when he declares that they are spiritual, he means to include in that term quite a large number of different properties. When the whole universe is declared to be spiritual, it is meant not only that it is in some sense conscious, but that it has what we recognise in ourselves as the higher forms of consciousness. That it is intelligent; that it is purposeful; that it is not mechanical; all these different things are commonly asserted of it. In general, it may be said, this phrase 'reality is spiritual' excites and expresses the belief that the whole universe possesses all the qualities the possession of which is held to make us so superior to things which seem to be inanimate: at least, if it does not possess exactly those which we possess, it possesses not one only, but several others, which, by the same ethical standard, would be judged equal to or better than our own. When we say it is spiritual we mean to say that it has quite a number of excellent qualities, different from any which we commonly attribute either to stars or planets or to cups and saucers.

Now why I mention these two points is that when engaged in the intricacies of philosophic discussion, we are apt to overlook the vastness of the difference between this idealistic view and the ordinary view of the world, and to overlook the number of different propositions which the idealist must prove. It is, I think, owing to the vastness of this difference and owing to the number of different excellences which Idealists attribute to the universe, that it seems such an interesting and important question whether Idealism be true or not. But, when we begin to argue about it, I think we are apt to forget what a vast number of arguments this interesting question must involve: we are apt to assume, that if one or two points be made on either side, the whole case is won. I say this lest it should be thought that any of the arguments which will be advanced in this paper would be sufficient to disprove, or any refutation of them sufficient to prove, the truly interesting and important proposition that reality is spiritual. For my own part I wish it to be clearly understood that I do not suppose that anything I shall say has the smallest tendency to prove that reality is not spiritual: I do not believe it possible to refute a single one of the many important propositions contained in the assertion that it is so. Reality may be spiritual, for all I know; and I devoutly hope it is. But I take 'Idealism' to be a wide term and to include not only this interesting conclusion but a number of arguments which are supposed to be, if not sufficient, at least necessary, to prove it. Indeed I take it that modern Idealists are chiefly distinguished by certain arguments which they have in common. That reality is spiritual has, I believe, been the tenet of many theologians; and yet, for believing that alone, they should hardly be called Idealists. There are besides, I believe, many persons, not improperly called Idealists, who hold certain characteristic propositions, without venturing to think them quite sufficient to prove so grand a conclusion. It is, therefore, only with Idealistic arguments that I am concerned; and if any Idealist holds that no argument is necessary to prove that reality is spiritual, I shall certainly not have refuted him. I shall, however, attack at least one argument, which, to the best of my belief, is considered necessary to their position by all Idealists. And I wish to point out a certain advantage which this procedure gives me—an advantage which justifies the assertion that, if my arguments are sound, they will have refuted Idealism. If I can refute a single proposition which is a necessary and essential step in all Idealistic arguments, then, no matter how good the rest of these arguments may be, I shall have proved that Idealists have no reason whatever for their conclusion.

Suppose we have a chain of argument which takes the form: Since A is B, and B is C, and C is D, it follows A is D. In such an argument, though 'B is C' and 'C is D' may both be perfectly true, yet if 'A is B' be false, we have no more reason for asserting A is D than if all three were false. It does not, indeed, follow that A is D is false; nor does it follow that no other arguments would prove it to be true. But it does follow that, so far as this argument goes, it is the barest supposition, without the least bit of evidence. I propose to attack a proposition which seems to me to stand in this relation to the conclusion 'Reality is spiritual.' I do not propose to dispute that 'Reality is spiritual;' I do not deny that there may be reasons for thinking that it is: but I do propose to show that one reason upon which, to the best of my judgment, all other arguments ever used by Idealists depend is false. These other arguments may, for all I shall say, be eminently ingenious and true; they are very many and various, and different Idealists use the most different arguments to prove the same most important conclusions. Some of these may be sufficient to prove that B is C and C is D; but if, as I shall try to show, their 'A is B' is false the conclusion A is D remains a pleasant supposition. I do not deny that to suggest pleasant and plausible suppositions may be the proper function of philosophy: but I am assuming that the name Idealism can only be properly applied where there is a certain amount of argument, intended to be cogent.

The subject of this paper is, therefore, quite uninteresting. Even if I prove my point, I shall have proved nothing about the Universe in general. Upon the important question whether Reality is or is not spiritual my argument will not have the remotest bearing. I shall only attempt to arrive at the truth about a matter, which is in itself quite trivial and insignificant, and from which, so far as I can see and certainly so far as I shall say, no conclusions can be drawn about any of the subjects about which we most want to know. The only importance I can claim for the subject I shall investigate is that it seems to me to be a matter upon which not Idealists only, but all philosophers and psychologists also, have been in error, and from their erroneous view of which they have inferred (validly or invalidly) their most striking and interesting conclusions. And that it has even this importance I cannot hope to prove. If it has this importance, it will indeed follow that all the most striking results of philosophy—Sensationalism. Agnosticism and Idealism alike—have, for all that has hitherto been urged in their favour, no more foundation than the supposition that a chimera lives in the moon. It will follow that, unless new reasons never urged hitherto can be found, all the most important philosophic doctrines have as little claim to assent as the most superstitious beliefs of the lowest savages. Upon the question what we have reason to believe in the most interesting matters, I do therefore think that my results will have an important bearing; but I cannot too clearly insist that upon the question whether these beliefs are true they will have none whatever.

The trivial proposition which I propose to dispute is this: that esse is percipi. This is a very ambiguous proposition, but, in some sense or other, it has been very widely held. That it is, in some sense, essential to Idealism, I must for the present merely assume. What I propose to show is that, in all the senses ever given to it, it is false.

But, first of all, it may be useful to point out briefly in what relation I conceive it to stand to Idealistic arguments. That wherever you can truly predicate esse you can truly predicate percipi, in some sense or other, is, I take it, a necessary step In all arguments, properly to be called Idealistic, and, what is more, in all arguments hitherto offered for the Idealistic conclusion. If esse is percipi, this is at once equivalent to saying that whatever is, is experienced; and this, again, is equivalent, in a sense, to saying that whatever is, is something mental. But this is not the sense in which the Idealist conclusion must maintain that Reality is mental. The Idealist conclusion is that esse is percipere; and hence, whether esse be percipi or not, a further and different discussion is needed to show whether or not it is also percipere. And again, even if esse be percipere, we need a vast quantity of further argument to show that what has esse has also those higher mental qualities which are denoted by spiritual. This is why I said that the question I should discuss, namely, whether or not esse is percipi, must be utterly insufficient either to prove or to disprove that reality is spiritual. But, on the other hand, I believe that every argument ever used to show that reality is spiritual has inferred this (validly or invalidly) from 'esse is percipere' as one of its premisses; and that this again has never been pretended to be proved except by use of the premiss that esse is percipi. The type of argument used for the latter purpose is familiar enough. It is said that since whatever is, is experienced, and since some things are which are not experienced by the individual, these must at least form part of some experience. Or again that, since an object necessarily implies a subject, and since the whole world must be an object, we must conceive it to belong to some subject or subjects, in the same sense in which whatever is the object of our experience belongs to us. Or again, that, since thought enters into the essence of all reality, we must conceive behind it, in it, or as its essence, a spirit akin to ours, who think: that 'spirit greets spirit' in its object. Into the validity of these inferences I do not propose to enter: they obviously require a great deal of discussion. I only desire to point out that, however correct they may be, yet if esse is not percipi, they leave us as far from a proof that reality is spiritual, as if they were all false too.

But now: Is esse percipi? There are three very ambiguous terms in this proposition, and I must begin by distinguishing the different things that may be meant by some of them.

And first with regard to percipi. This term need not trouble us long at present. It was, perhaps, originally used to mean 'sensation' only; but I am not going to be so unfair to modern Idealists—the only Idealists to whom the term should now be applied without qualification—as to hold that, if they say esse is percipi, they mean by percipi sensation only. On the contrary I quite agree with them that, if esse be percipi at all, percipi must be understood to include not sensation only, but that other type of mental fact, which is called 'thought '; and, whether esse be percipi or not, I consider it to be the main service of the philosophic school, to which modern Idealists belong, that they have insisted on distinguishing 'sensation' and 'thought' and on emphasising the importance of the latter. Against Sensationalism and Empiricism they have maintained the true view. But the distinction between sensation and thought need not detain us here. For, in whatever respects they differ, they have at least this in common, that they are both forms of consciousness or, to use a term that seems to be more in fashion just now, they are both ways of experiencing. Accordingly, whatever esse is percipi may mean, it does at least assert that whatever is, is experienced. And since what I wish to maintain is, that even this is untrue, the question whether it be experienced by way of sensation or thought or both is for my purpose quite irrelevant. If it be not experienced at all, it cannot be either an object of thought or an object of sense. It is only if being involves 'experience' that the question, whether it involves sensation or thought or both, becomes important. I beg, therefore, that percipi may be understood, in what follows, to refer merely to what is common to sensation and thought. A very recent article states the meaning of esse is percipi with all desirable clearness in so far as percipi is concerned.

'I will undertake to show,' says Mr. Taylor,[1] 'that what makes [any piece of fact] real can be nothing but its presence as an inseparable aspect of a sentient experience.' I am glad to think that Mr. Taylor has been in time to supply me with so definite a statement that this is the ultimate premiss of Idealism. My paper will at least refute Mr. Taylor's Idealism, if it refutes anything at all: for I shall undertake to show that what makes a thing real cannot possibly be its presence as an inseparable aspect of a senient experience.

But Mr. Taylor's statement though clear, I think, with regard to the meaning of percipi is highly ambiguous in other respects. I will leave it for the present to consider the next ambiguity in the statement: Esse is percipi. What does the copula mean? What can be meant by saying that Esse is percipi? There are just three meanings, one or other of which such a statement must have, if it is to be true; and of these there is only one which it can have, if it is to be important. (1) The statement may be meant to assert that the word 'esse' is used to signify nothing either more or less than the word 'percipi': that the two words are precise synonyms: that they are merely different names for one and the same thing: that what is meant by esse is absolutely identical with what is meant by percipi. I think I need not prove that the principle esse is percipi is not thus intended merely to define a word; nor yet that, if it were, it would be an extremely bad definition. But if it does not mean this, only two alternatives remain. The second is (2) that what is meant by esse, though not absolutely identical with what is meant by percipi, yet includes the latter as a part of its meaning. If this were the meaning of 'esse is percipi,' then to say that a thing was real would not be the same thing as to say that it was experienced. That it was real would mean that it was experienced and something else besides: 'being experienced' would be analytically essential to reality, but would not be the whole meaning of the term. From the fact that a thing was real we should be able to infer, by the law of contradiction, that it was experienced; since the latter would be part of what is meant by the former. But, on the other hand, from the fact a thing was experienced we should not be able to infer that it was real; since it would not follow from the fact that it had one of the attributes essential to reality, that it also had the other or others. Now, if we understand esse is percipi in this second sense, we must distinguish three different things which it asserts. First of all, it gives a definition of the word 'reality,' asserting that word stands for a complex whole, of which what is meant by 'percipi' forms a part. And secondly it asserts that 'being experienced' forms a part of a certain whole. Both these propositions may be true, and at all events I do not wish to dispute them. I do not, indeed, think that the word 'reality' is commonly used to include 'percipi': but I do not wish to argue about the meaning of words. And that many things which are experienced are also something else—that to be experienced forms part of certain wholes, is, of course, indisputable. But what I wish to point out is, that neither of these propositions is of any importance, unless we add to them a third. That 'real' is a convenient name for a union of attributes which sometimes occurs, it could not be worth any one's while to assert: no inferences of any importance could be drawn from such an assertion. Our principle could only mean that when a thing happens to have percipi as well as the other qualities included under esse, it has percipi: and we should never be able to infer that it was experienced, except from a proposition which already asserted that it was both experienced and something else. Accordingly, if the assertion that percipi forms part of the whole meant by reality is to have any importance, it must mean that the whole is organic, at least in this sense, that the other constituent or constituents of it cannot occur without percipi, even if percipi can occur without them. Let us call these other constituents x. The proposition that esse includes percipi, and that therefore from esse percipi can be inferred, can only be important if it is meant to assert that percipi can be inferred from x. The only importance of the question whether the whole esse includes the part percipi rests therefore on the question whether the part x is necessarily connected with the part percipi. And this is (3) the third possible meaning of the assertion esse is percipi: and, as we now see, the only important one. Esse is percipi asserts that wherever you have x you also have percipi that whatever has the property x also has the property that it is experienced. And this being so, it will be convenient if, for the future, I may be allowed to use the term 'esse' to denote x alone. I do not wish thereby to beg the question whether what we commonly mean by the word 'real' does or does not include percipi as well as x. I am quite content that my definition of 'esse' to denote x, should be regarded merely as an arbitrary verbal definition. Whether it is so or not, the only question of interest is whether from x percipi can be inferred, and I should prefer to be able to express this in the form: can percipi be inferred from esse? Only let it be understood that when I say esse, that term will not for the future include percipi: it denotes only that x, which Idealists, perhaps rightly, include along with percipi under their term esse. That there is such an x they must admit on pain of making the proposition an absolute tautology; and that from this x percipi can be inferred they must admit, on pain of making it a perfectly barren analytic proposition. Whether x done should or should not be called esse is not worth a dispute: what is worth dispute is whether percipi is necessarily connected with x.

We have therefore discovered the ambiguity of the copula in esse is percipi, so far as to see that this principle asserts two distinct terms to be so related, that whatever has the one, which I call esse, has also the property that it is experienced. It asserts a necessary connexion between esse on the one hand and percipi on the other; these two words denoting each a distinct term, and esse denoting a term in which that denoted by percipi is not included. We have, then in esse is percipi, a necessary synthetic proposition which I have undertaken to refute. And I may say at once that, understood as such, it cannot be refuted. If the Idealist chooses to assert that it is merely a self-evident truth, I have only to say that it does not appear to me to be so. But I believe that no Idealist ever has maintained it to be so. Although this—that two distinct terms are necessarily related—is the only sense which 'esse is percipi' can have if it is to be true and important, it can have another sense, if it is to be an important falsehood. I believe that Idealists all hold this important falsehood. They do not perceive that Esse is percipi must, if true, be merely a self-evident synthetic truth: they either identify with it or give as a reason for it another proposition which must be false because it is self-contradictory. Unless they did so, they would have to admit that it was a perfectly unfounded assumption; and if they recognised that it was unfounded, I do not think they would maintain its truth to be evident. Esse is percipi, in the sense I have found for it, may indeed be true; I cannot, refute it: but if this sense were clearly apprehended, no one, I think, would believe that it was true.

Idealists, we have seen, must assert that whatever is experienced, is necessarily so. And this doctrine they commonly express by saying that 'the object of experience is inconceivable apart from the subject.' I have hitherto been concerned with pointing out what meaning this assertion must have, if it is to be an important truth. I now propose to show that it may have an important meaning, which must be false, because it is self-contradictory.

It is a well-known fact in the history of philosophy that necessary truths in general, but especially those of which it is said that the opposite is inconceivable, have been commonly supposed to be analytic, in the sense that the proposition denying them was self-contradictory. It was in this way, commonly supposed, before Kant, that many truths could be proved by the law of contradiction alone. This is, therefore, a mistake which it is plainly easy for the best philosophers to make. Even since Kant many have continued to assert it; but I am aware that among those Idealists, who most properly deserve the name, it has become more fashionable to assert that truths are both analytic and synthetic. Now with many of their reasons for asserting this I am not concerned: it is possible that in some connexions the assertion may bear a useful and true sense. But if we understand 'analytic' in the sense just defined, namely, what is proved by the law of contradiction alone, it is plain that, if 'synthetic' means what is not proved by this alone, no truth can be both analytic and synthetic. Now it seems to me that those who do maintain truths to be both, do nevertheless maintain that they are so in this as well as in other senses. It is, indeed, extremely unlikely that so essential a part of the historical meaning of 'analytic' and 'synthetic' should have been entirely discarded, especially since we find no express recognition that it is discarded. In that case it is fair to suppose that modern Idealists have been influenced by the view that certain truths can be proved by the law of contradiction alone. I admit they also expressly declare that they can not: but this is by no means sufficient to prove that they do not also think they are; since it is very easy to hold two mutually contradictory opinions. What I suggest then is that Idealists hold the particular doctrine in question, concerning the relation of subject and object in experience, because they think it is an analytic truth in this restricted sense that it is proved by the law of contradiction alone.

I am suggesting that the Idealist maintains that object and subject are necessarily connected, mainly because he fails to see that they are distinct, that they are two, at all. When he thinks of 'yellow' and when he thinks of the 'sensation of yellow,' he fails to see that there is anything whatever in the latter which is not in the former. This being so, to deny that yellow can ever be apart from the sensation of yellow is merely to deny that yellow can ever be other than it is; since yellow and the sensation of yellow are absolutely identical. To assert that yellow is necessarily an object of experience is to assert that yellow is necessarily yellow—a purely identical proposition, and therefore proved by the law of contradiction alone. Of course, the proposition also implies that experience is, after all, something distinct from yellow—else there would be no reason for insisting that yellow is a sensation: and that the argument thus both affirms and denies that yellow and sensation of yellow are distinct, is what sufficiently refutes it. But this contradiction can easily be overlooked, because though we are convinced, in other connexions, that 'experience' does mean something and something most important, yet we are never distinctly aware what it means, and thus in every particular case we do not notice its presence. The facts present themselves as a kind of antinomy:

(1) Experience is something unique and different from anything else; (2) Experience of green is entirely indistinguishable from green; two propositions which cannot both be true. Idealists, holding both, can only take refuge in arguing from the one in some connexions and from the other in others.

But I am well aware that there are many Idealists who would repel it as an utterly unfounded charge that they fail to distinguish between a sensation or idea and what I will call its object. And there are, I admit, many who not only imply, as we all do, that green is distinct from the sensation of green, but expressly insist upon the distinction as an important part of their system. They would perhaps only assert that the two form an inseparable unity. But I wish to point out that many, who use this phrase, and who do admit the distinction, are not thereby absolved from the charge that they deny it. For there is a certain doctrine, very prevalent among philosophers nowadays, which by a very simple reduction may be seen to assert that two distinct things both are and are not distinct. A distinction is asserted; but it is also asserted that the things distinguished form an 'organic unity,' But, forming such a unity, it is held, each would not be what it is apart from its relation to the other. Hence to consider either by itself is to make an illegitimate abstraction. The recognition that there are 'organic unities' and 'illegitimate abstractions' in this sense is regarded as one of the chief conquests of modern philosophy. But what is the sense attached to these terms? An abstraction is illegitimate, when and only when we attempt to assert of a part—of something abstracted—that which is true only of the whole to which it belongs: and it may perhaps be useful to point out that this should not be done. But the application actually made of this principle, and what perhaps would be expressly acknowledged as its meaning, is something much the reverse of useful. The principle is used to assert that certain abstractions are in all cases illegitimate; that whenever you try to assert anything whatever of that which is part of an organic whole, what you assert can only be true of the whole. And this principle, so far from being a useful truth, is necessarily false. For if the whole can, nay must, be substituted for the part in all propositions and for all purposes, this can only be because the whole is absolutely identical with the part. When, therefore, we are told that green and the sensation of green are certainly distinct but yet are not separable, or that it is an illegitimate abstraction to consider the one apart from the other, what these provisos are used to assert is, that though the two things are distinct yet you not only can but must treat them as if they were not. Many philosophers, therefore, when they admit a distinction, yet (following the lead of Hegel) boldly assert their right, in a slightly more obscure form of words, also to deny it. The principle of organic unities, like that of combined analysis and synthesis, is mainly used to defend the practice of holding both of two contradictory propositions, wherever this may seem convenient. In this, as in other matters, Hegel's main service to philosophy has consisted in giving a name to and erecting into a principle, a type of fallacy to which experience had shown philosophers, along with the rest of mankind, to be addicted. No wonder that he has followers and admirers.

I have shown then, so far, that when the Idealist asserts the important principle 'Esse is percipi' he must, if it is to be true, mean by this that: Whatever is experienced also must be experienced. And I have also shown that he may identify with, or give as a reason for, this proposition, one which must be false, because it is self contradictory. But at this point I propose to make a complete break in my argument. 'Esse is percipi,' we have seen, asserts of two terms, as distinct from one another as 'green' and 'sweet,' that whatever has the one has also the other: it asserts that 'being' and 'being experienced' are necessarily connected: that whatever is is also experienced. And this, I admit, cannot be directly refuted. But I believe it to be false; and I have asserted that anybody who saw that 'esse and percipi' were as distinct as 'green' and 'sweet' would be no more ready to believe that whatever is is also experienced, than to believe that whatever is green is also sweet. I have asserted that no one would believe that 'esse is percipi' if they saw how different esse is from percipi: but this I shall not try to prove. I have asserted that all who do believe that 'esse is percipi' identify with it or take as a reason for it a self-contradictory proposition: but this I shall not try to prove. I shall only try to show that certain propositions which I assert to be believed, are false. That they are believed, and that without this belief 'esse is percipi' would not be believed either, I must leave without a proof.

I pass, then, from the uninteresting question 'Is 'esse percipi?' to the still more uninteresting and apparently irrelevant question 'What is a sensation or idea?'

We all know that the sensation of blue differs from that of green. But it is plain that if both are sensations they also have some point in common. What is it that they have in common? And how is this common element related to the points in which they differ?

I will call the common element 'consciousness' without yet attempting to say what the thing I so call is. We have then in every sensation two distinct terms, (1) 'consciousness,' in respect of which all sensations are alike; and (2) something else, in respect of which one sensation differs from another. It will be convenient if I may be allowed to call this second term the 'object' of a sensation: this also without yet attempting to say what I mean by the word.

We have then in every sensation two distinct elements, one which I call consciousness, and another which I call the object of consciousness. This must be so if the sensation of blue and the sensation of green, though different in one respect, are alike in another: blue is one object of sensation and green is another, and consciousness, which both sensations have in common, is different from either.

But, further, sometimes the sensation of blue exists in my mind and sometimes it does not; and knowing, as we now do, that the sensation of blue includes two different elements, namely consciousness and blue, the question arises whether, when the sensation of blue exists, it is the consciousness which exists, or the blue which exists, or both. And one point at least is plain: namely that these three alternatives are all different from one another. So that, if any one tells us that to say 'Blue exists' is the same thing as to say that 'Both blue and consciousness exist,' he makes a mistake and a self-contradictory mistake.

But another point is also plain, namely, that when the sensation exists, the consciousness, at least, certainly does exist; for when I say that the sensations of blue and of green both exist, I certainly mean that what is common to both and in virtue of which both are called sensations, exists in each case. The only alternative left, then, is that either both exist or the consciousness exists alone. If, therefore, any one tells us that the existence of blue is the same thing as the existence of the sensation of blue he makes a mistake and a self-contradictory mistake, for he asserts either that blue is the same thing as blue together with consciousness, or that it is the same thing as consciousness alone.

Accordingly to identify either "blue" or any other of what I have called "objects" of sensation, with the corresponding sensation is in every case, a self-contradictory error. It is to identify a part either with the whole of which it is a part or else with the other part of the same whole. If we are told that the assertion "Blue exists" is meaningless unless we mean by it that "The sensation of blue exists," we are told what is certainly false and self-contradictory. If we are told that the existence of blue is inconceivable apart from the existence of the sensation, the speaker probably means to convey to us, by this ambiguous expression, what is a self-contradictory error. For we can and must conceive the existence of blue as something quite distinct from the existence of the sensation. We can and must conceive that blue might exist and yet the sensation of blue not exist. For my own part I not only conceive this, but conceive it to be true. Either therefore this terrific assertion of inconceivability means what is false and self-contradictory or else it means only that as a matter of fact blue never can exist unless the sensation of it exists also.

And at this point I need not conceal my opinion that no philosopher has ever yet succeeded in avoiding this self-contradictory error: that the most striking results both of Idealism and of Agnosticism are only obtained by identifying blue with the sensation of blue: that esse is held to be percipi, solely because what is experienced is held to be identical with the experience of it. That Berkeley and Mill committed this error will, perhaps, be granted: that modern Idealists make it will, I hope, appear more probable later. But that my opinion is plausible, I will now offer two pieces of evidence. The first is that language offers us no means of referring to such objects as "blue" and "green" and "sweet," except by calling them sensations: it is an obvious violation of language to call them "things" or "objects" or "terms." And similarly we have no natural means of referring to such objects as "causality" or "likeness" or "identity," except by calling them "ideas" or "notions" or "conceptions." But it is hardly likely that if philosophers had clearly distinguished in the past between a sensation or idea and what I have called its object, there should have been no separate name for the latter. They have always used the same name for these two different "things" (if I may call them so): and hence there is some probability that they have supposed these "things" not to be two and different, but one and the same. And, secondly, there is a very good reason why they should have supposed so, in the fact that when we refer to introspection and try to discover what the sensation of blue is, it is very easy to suppose that we have before us only a single term. The term "blue" is easy enough to distinguish, but the other element which I have called "consciousness"—that which sensation of blue has in common with sensation of green—is extremely difficult to fix. That many people fail to distinguish it at all is sufficiently shown by the fact that there are materialists. And, in general, that which makes the sensation of blue a mental fact seems to escape us: it seems, if I may use a metaphor, to be transparent—we look through it and see nothing but the blue; we may be convinced that there is something but what it is no philosopher, I think, has yet clearly recognised.

But this was a digression. The point I had established so far was that in every sensation or idea we must distinguish two elements, (1) the "object," or that in which one differs from another; and (2) "consciousness," or that which all have in common—that which makes them sensations or mental facts. This being so, it followed that when a sensation or idea exists, we have to choose between the alternatives that either object alone, or consciousness alone, or both, exist; and I showed that of these alternatives one, namely that the object only exists, is excluded by the fact that what we mean to assert is certainly the existence of a mental fact. There remains the question: Do both exist? Or does the consciousness alone? And to this question one answer has hitherto been given universally: That both exist.

This answer follows from the analysis hitherto accepted of the relation of what I have called "object" to "consciousness" in any sensation or idea. It is held that what I call the object is merely the "content" of a sensation or idea. It is held that in each case we can distinguish two elements and two only, (1) the fact that there is feeling or experience, and (2) what is felt or experienced; the sensation or idea, it is said, forms a whole, in which we must distinguish two "inseparable aspects," "content" and "existence." I shall try to show that this analysis is false; and for that purpose I must ask what may seem an extraordinary question: namely what is meant by saying that one thing is "content" of another? It is not usual to ask this question; the term is used as if everybody must understand it. But since I am going to maintain that "blue" is not the content of the sensation of blue, and what is more important, that, even if it were this analysis would leave out the most important element in the sensation of blue, it is necessary that I should try to explain precisely what it is that I shall deny.

What then is meant by saying that one thing is the "content" of another? First of all I wish to point out that "blue" is rightly and properly said to be part of the content of a blue flower. If, therefore, we also assert that it is part of the content of the sensation of blue, we assert that it has to the other parts (if any) of this whole the same relation which it has to the other parts of a blue flower—and we assert only this: we cannot mean to assert that it has to the sensation of blue any relation which it does not have to the blue flower. And we have seen that the sensation of blue contains at least one other element beside blue—namely, what I call "consciousness," which makes it a sensation. So far then as we assert that blue is the content of the sensation, we assert that it has to this "consciousness" the same relation which it has to the other parts of a blue flower: we do assert this, and we assert no more than this. Into the question what exactly the relation is between blue and a blue flower in virtue of which we call the former part of its "content" I do not propose to enter. It is sufficient for my purpose to point out that it is the general relation most commonly meant when we talk of a thing and its qualities; and that this relation is such that to say the thing exists implies that the qualities also exist. The content of the thing is what we assert to exist, when we assert that the thing exists.

When, therefore, blue is said to be part of the content of the "sensation of blue," the latter is treated as if it were a whole constituted in exactly the same way as any other "thing." The "sensation of blue," on this view, differs from a blue bead or a blue beard, in exactly the same way in which the two latter differ from one another: the blue bead differs from the blue beard, in that while the former contains glass, the latter contains hair; and the "sensation of blue" differs from both in that, instead of glass or hair, it contains consciousness. The relation of the blue to the consciousness is conceived to be exactly the same as that of the blue to the glass or hair: it is in all three cases the quality of a thing.

But I said just now that the sensation of blue was analysed into "content" and "existence," and that blue was said to be the content of the idea of blue. There is an ambiguity in this and a possible error, which I must note in passing. The term "content" may be used in two senses. If we use "content" as equivalent to what Mr. Bradley calls the "what"—if we mean by it the whole of what is said to exist, when the thing is said to exist, then blue is certainly not the content of the sensation of blue: part of the content of the sensation is, in this sense of the term, that other element which I have called consciousness. The analysis of this sensation into the "content" "blue," on the one hand, and mere existence on the other, is therefore certainly false; in it we have again the self-contradictory identification of "Blue exists" with "The sensation of blue exists," But there is another sense in which "blue" might properly be said to be the content of the sensation—namely, the sense in which "content," like εἴδος is opposed to "substance" or "matter." For the element "consciousness," being common to all sensations, may be and certainly is regarded as in some sense their "substance," and by the "content" of each is only meant that in respect of which one differs from another. In this sense then "blue" might be said to be the content of the sensation; but, in that case, the analysis into "content" and "existence" is, at least, misleading, since under "existence" must be included "what exists" in the sensation other than blue.

We have it, then, as a universally received opinion that blue is related to the sensation or idea of blue, as its content, and that this view, if it is to be true, must mean that blue is part of what is said to exist when we say that the sensation exists. To say that the sensation exists is to say both that blue exists and that "consciousness," whether we call it the substance of which blue is the content or call it another part of the content, exists too. Any sensation or idea is a "thing," and what I have called its object is the quality of this thing. Such a "thing" is what we think of when we think of a mental image. A mental image is conceived as if it were related to that of which it is the image (if there be any such thing) in exactly the same way as the image in a looking-glass is related to that of which it is the reflection; in both cases there is identity of content, and the image in the looking-glass differs from that in the mind solely in respect of the fact that in the one case the other constituent of the image is "glass" and in the other case it is consciousness. If the image is of blue, it is not conceived that this "content" has any relation to the consciousness but what it has to the glass: it Is conceived merely to be its content. And owing to the fact that sensations and ideas are all considered to be wholes of this description—things in the mind—the question: What do we know? is considered to be identical with the question: What reason have we for supposing that there are things outside the mind corresponding to these that are inside it?

What I wish to point out is (1) that we have no reason for supposing that there are such things as mental images at all—for supposing that blue is part of the content of the sensation of blue, and (2) that even if there are mental images, no mental image and no sensation or idea is merely a thing of this kind: that 'blue,' even if it is part of the content of the image or sensation or idea of blue, is always also related to it in quite another way, and that this other relation, omitted in the traditional analysis, is the only one which makes the sensation of blue a mental fact at all.

The true analysis of a sensation or idea is as follows. The element that is common to them all, and which I have called "consciousness," really is consciousness. A sensation is, in reality, a case of 'knowing' or 'being aware of' or 'experiencing' something. When we know that the sensation of blue exists, the fact we know is that there exists an awareness of blue. And this awareness is not merely, as we have hitherto seen it must be, itself something distinct and unique, utterly different from blue: it also has a perfectly distinct and unique relation to blue, a relation which is not that of thing or substance to content, nor of one part of content to another part of content. This relation is just that which we mean in every case by 'knowing.' To have in your mind 'knowledge' of blue, is not to have in your mind a 'thing' or 'image' of which blue is the content. To be aware of the sensation of blue is not to be aware of a mental image—of a "thing," of which 'blue' and some other element are constituent parts in the same sense in which blue and glass are constituents of a blue bead. It is to be aware of an awareness of blue; awareness being used, in both cases, in exactly the same sense. This element, we have seen, is certainly neglected by the 'content' theory: that theory entirely fails to express the fact that there is, in the sensation of blue, this unique relation between blue and the other constituent. And what I contend is that this omission is not mere negligence of expression, but is due to the fact that though philosophers have recognised that something distinct is meant by consciousness, they have never yet had a clear conception of what that something is. They have not been able to hold it and blue before their minds and to compare them, in the same way in which they can compare blue and green. And this for the reason I gave above: namely that the moment we try to fix our attention upon consciousness and to see what, distinctly, it is, it seems to vanish: it seems as if we had before us a mere emptiness. When we try to introspect the sensation of blue, all we can see is the blue: the other element is as if it were diaphanous. Yet it can be distinguished if we look attentively enough, and if we know that there is something to look for. My main object in this paragraph has been to try to make the reader see it; but I fear I shall have succeeded very ill.

It being the case, then, that the sensation of blue includes in its analysis, beside blue, both a unique element 'awareness' and a unique relation of this element to blue, I can make plain what I meant by asserting, as two distinct propositions, (1) that blue is probably not part of the content of the sensation at all, and (2) that, even it were, the sensation would nevertheless not be the sensation of blue, if blue had only this relation to it. The first hypothesis may now be expressed by saying that, if it were true, then, when the sensation of blue exists, there exists a blue awareness: offence may be taken at the expression, but yet it expresses just what should be and is meant by saying that blue is, in this case, a content of consciousness or experience. Whether or not, when I have the sensation of blue, my consciousness or awareness is thus blue, my introspection does not enable me to decide with certainty: I only see no reason for thinking that it is. But whether it is or not, the point is unimportant, for introspection does enable me to decide that something else is also true: namely that I am aware of blue, and by this I mean, that my awareness has to blue a quite different and distinct relation. It is possible, I admit, that my awareness is blue as well as being of blue: but what I am quite sure of is that it is of blue; that it has to blue the simple and unique relation the existence of which alone justifies us in distinguishing knowledge of a thing from the thing known, indeed in distinguishing mind from matter. And this result I may express by saying that what is called the content of a sensation is in very truth what I originally called it—the sensation's object.

But, if all this be true, what follows?

Idealists admit that some things really exist of which they are not aware: there are some things, they hold, which are not inseparable aspects of their experience, even if they be inseparable aspects of some experience. They further hold that some of the things of which they are sometimes aware do really exist, even when they are not aware of them: they hold for instance that they are sometimes aware of other minds, which continue to exist even when they are not aware of them. They are, therefore, sometimes aware of something which is not an inseparable aspect of their own experience. They do know some things which are not a mere part or content of their experience. And what my analysis of sensation has been designed to show is, that whenever I have a mere sensation or idea, the fact is that I am then aware of something which is equally and in the same sense not an inseparable aspect of my experience. The awareness which I have maintained to be included in sensation is the very same unique fact which constitutes every kind of knowledge: "blue" is as much an object, and as little a mere content, of my experience, when I experience it, as the most exalted and independent real thing of which I am ever aware. There is, therefore, no question of how we are to "get outside the circle of our own ideas and sensations." Merely to have a sensation is already to be outside that circle. It is to know something which is as truly and really not a part of my experience, as anything which I can ever know.

Now I think I am not mistaken in asserting that the reason why Idealists suppose that everything which is must be an inseparable aspect of some experience, is that they suppose some things, at least, to be inseparable aspects of their experience. And there is certainly nothing which they are so firmly convinced to be an inseparable aspect of their experience as what they call the content of their ideas and sensations. If, therefore, this turns out in every case, whether it be also the content or not, to be at least not an inseparable aspect of the experience of it, it will be readily admitted that nothing else which we experience ever is such an inseparable aspect. But if we never experience anything but what is not an inseparable aspect of that experience, how can we infer that anything whatever, let alone everything, is an inseparable aspect of any experience? How utterly unfounded is the assumption that "esse is percipi" appears in the clearest light.

But further I think it may be seen that if the object of an Idealist's sensation were, as he supposes, not the object but merely the content of that sensation, if, that is to say, it really were an inseparable aspect of his experience, each Idealist could never be aware either of himself or of any other real thing. For the relation of a sensation to its object is certainly the same as that of any other instance of experience to its object; and this, I think, is generally admitted even by Idealists: they state as readily that what is judged or thought or perceived is the content of that judgment or thought or perception, as that blue Is the content of the sensation of blue. But, if so, then when any Idealist thinks he is aware of himself or of any one else, this cannot really be the case. The fact Is, on his own theory, that himself and that other person are in reality mere contents of an awareness, which is aware of nothing whatever. All that can be said is that there is an awareness in him, with a certain content: it can never be true that there is in him a consciousness of anything. And similarly he is never aware either of the fact that he exists or that reality is spiritual. The real fact, which he describes in those terms, is that his existence and the spirituality of reality are contents of an awareness, which is aware of nothing—certainly not, then, of it own content.

And further if everything, of which he thinks he is aware, is in reality merely a content of his own experience he has certainly no reason for holding that anything does exist except himself: it will, of course, be possible that other persons do exist; solipsism will not be necessarily true; but he cannot possibly infer from anything he holds that it is not true. That he himself exists will of course follow from his premiss that many things are contents of his experience. But since everything, of which he thinks himself aware, is in reality merely an inseparable aspect of that awareness; this premiss allows no inference that any of these contents, far less any other consciousness, exists at all except as an inseparable aspect of his awareness, that is, as part of himself.

Such, and not those which he takes to follow from it, are the consequences which do follow from the Idealist's supposition that the object of an experience is in reality merely a content or inseparable aspect of that experience. If, on the other hand, we clearly recognise the nature of that peculiar relation which I have called "awareness of anything"; if we see that this is involved equally in the analysis of every experience—from the merest sensation to the most developed perception or reflexion, and that this is in fact the only essential element in an experience—the only thing that is both common and peculiar to all experiences—the only thing which gives us reason to call any fact mental; if, further, we recognise that this awareness is and must be in all cases of such a nature that its object, when we are aware of it, is precisely what it would be, if we were not aware: then it becomes plain that the existence of a table in space is related to my experience of it in precisely the same way as the existence of my own experience is related to my experience of that. Of both we are merely aware: if we are aware that the one exists, we are aware in precisely the same sense that the other exists; and if it is true that my experience can exist, even when I do not happen to be aware of its existence, we have exactly the same reason for supposing that the table can do so also. When, therefore, Berkeley, supposed that the only thing of which I am directly aware is my own sensations and ideas, he supposed what was false; and when Kant supposed that the objectivity of things in space consisted in the fact that they were "Vorstellungen" having to one another different relations from those which the same "Vorstellungen" have to one another in subjective experience, he supposed what was equally false. I am as directly aware of the existence of material things in space as of my own sensations; and what I am aware of with regard to each is exactly the same—namely that in one case the material thing, and in the other case my sensation does really exist. The question requiring to be asked about material things is thus not: What reason have we for supposing that anything exists corresponding to our sensations? but: What reason have we for supposing that material things do not exist, since their existence has precisely the same evidence as that of our sensations? That either exist may be false; but if it is a reason for doubting the existence of matter, that it is an inseparable aspect of our experience, the same reasoning will prove conclusively that our experience does not exist either, since that must also be an inseparable aspect of our experience of it. The only reasonable alternative to the admission that matter exists as well as spirit, is absolute Scepticism—that, as likely as not nothing exists at all. All other suppositions—the Agnostic's, that something, at all events, does exist, as much as the Idealist's, that spirit does—are, if we have no reason for believing in matter, as baseless as the grossest superstitions.

THE NATURE AND REALITY OF OBJECTS OF PERCEPTION

There are two beliefs in which almost all philosophers, and almost all ordinary people are agreed. Almost everyone believes that he himself and what he directly perceives do not constitute the whole of reality: he believes that something other than himself and what he directly perceives exists or is real. I do not mean to say that almost everyone believes that what he directly perceives is real: I only mean that he does believe that, whether what he directly perceives is real or not, something other than it and other than himself certainly is so. And not only does each of us thus agree in believing that something other than himself and what he directly perceives is real: almost everyone also believes that among the real things, other than himself and what he directly perceives, are other persons who have thoughts and perceptions in some respects similar to his own. That most people believe this I think I need scarcely try to show. But since a good many philosophers may appear to have held views contradictory of this one, I will briefly point out my reason for asserting that most philosophers, even among those (if any) who have believed the contradictory of this, have yet held this as well. Almost all philosophers tell us something about the nature of human knowledge and human perception. They tell us that we perceive so and so; that the nature or origin of our perceptions is such and such; or (as I have just been telling you) that men in general have such and such beliefs. It might, indeed, be said that we are not to interpret such language too strictly: that, though a philosopher talks about human knowledge and our perceptions, he only means to talk about his own. But in many cases a philosopher will leave no doubt upon this point, by expressly assuming that there are other perceptions, which differ in some respects from his own: such, for instance, is the case when (as is so common nowadays) a philosopher introduces psycho-genetic considerations into his arguments —considerations concerning the nature of the perceptions of men who existed before and at a much lower stage of culture than himself. Any philosopher, who uses such arguments, obviously assumes that perceptions other than his own have existed or been real. And even those philosophers who think themselves justified in the conclusion that neither their own perceptions nor any perceptions like theirs are ultimately real, would, I think admit, that phenomenally, at least, they are real, and are certainly more real than some other things.

Almost everyone, then, does believe that some perceptions other than his own, and which he himself does not directly perceive, are real; and believing this, he believes that something other than himself and what he directly perceives is real. But how do we know that anything exists except our own perceptions, and what we directly perceive? How do we know that there are any other people, who have perceptions in some respects similar to our own?

I believe that these two questions express very exactly the nature of the problem which it is my chief object, in this paper, to discuss. When I say these words to you, they will at once suggest to your minds the very question, to which I desire to find an answer; they will convey to you the very same meaning which I have before my mind, when I use the words. You will understand at once what question it is that I mean to ask. But, for all that, the words which I have used are highly ambiguous. If you begin to ask yourselves what I do mean by them, you will find that there are several quite different things which I might mean. And there is, I think, great danger of confusing these different meanings with one another. I think that philosophers, when they have asked this question in one sense, have often answered it in quite a different sense; and yet have supposed that the answer which they have given is an answer to the very same question which they originally asked. It is precisely because there is this ambiguity—this danger of confusion, in the words which I have used, that I have chosen to use them. I wish to point out as clearly as I can, not only what I do mean by them, but also some things which I do not mean; and I wish to make it clear that the questions which I do not mean to ask, are different questions from that which I do mean to ask.

I will take the second of my two questions, since there is in the other an additional ambiguity to which I do not now wish to call attention. My second question was: How do we know that there exist any other people who have perceptions in some respects similar to our own? What does this question mean?

Now I think you may have noticed that when you make a statement to another person, and he answers "How do you know that that is so?" he very often means to suggest that you do not know it. And yet, though he means to suggest that you do not know it, he may not for a moment wish to suggest that you do not believe it, nor even that you have not that degree or kind of conviction, which goes beyond mere belief, and which may be taken to be essential to anything which can properly be called knowledge. He does not mean to suggest for a moment that you are saying something which you do not believe to be true, or even that you are not thoroughly convinced of its truth. What he does mean to suggest is that what you asserted was not true, even though you may not only have believed it but felt sure that it was true. He suggests that you don't know it, in the sense that what you believe or feel sure of is not true.

Now I point this out, not because I myself mean to suggest that we don't know the existence of other persons, but merely in order to show that the word "know" is sometimes used in a sense in which it is not merely equivalent to "believe" or "feel sure of." When the question "How do you know that?" is asked, the questioner does not merely mean to ask "how do you come to believe that, or to be convinced of it?" He sometimes, and I think generally, means to ask a question with regard to the truth, and not with regard to the existence of your belief. And similarly when I ask the question "How do we know that other people exist?" I do not mean to ask "How do we come to believe in or be convinced of their existence?" I do not intend to discuss this question at all. I shall not ask what suggests to us our belief in the existence of other persons or of an external world; I shall not ask whether we arrive at it by inference or by "instinct" or in any other manner, which ever has been or may be suggested: I shall discuss no question of any kind whatever with regard to its origin, or cause, or the way in which it arises. These psychological questions are not what I propose to discuss. When I ask the question "How do we know that other people exist?" I do not mean:

"How does our belief in their existence arise?"

But if I do not mean this what do I mean P I have said that I mean to ask a question with regard to the truth of that belief; and the particular question which I mean to ask might be expressed in the words: What reason have we for our belief in the existence of other persons? But these are words which themselves need some explanation, and I will try to give it.

In the first place, then, when I talk of "a reason," I mean only a good reason and not a bad one. A bad reason is, no doubt, a reason, in one sense of the word; but I mean to use the word "reason" exclusively in the sense in which it is equivalent to "good reason." But what, then, is meant by a good reason for a belief? I think I can express sufficiently accurately what I mean by it in this connection, as follows:—A good reason for a belief is a proposition which is true, and which would not be true unless the belief were also true. We should, I think, commonly say that when a man knows such a proposition, he has a good reason for his belief; and, when he knows no such proposition, we should say that he has no reason for it. When he knows such a proposition, we should say he knows something which is a reason for thinking his belief to be true—something from which it could be validly inferred. And if, in answer to the question "How do you know so and so?" he were to state such a proposition, we should, I think, feel that he had answered the question which we meant to ask. Suppose, for instance, in answer to the question "How do you know that?" he were to say "I saw it in the Times." Then, if we believed that he had seen it in the Times, and also believed that it would not have been in the Times, unless it had been true, we should admit that he had answered our question. We should no longer doubt that he did know what he asserted, we should no longer doubt that his belief was true. But if, on the other hand, we believed that he had not seen it in the Times—if, for instance, we had reason to believe that what he saw was not the statement which he made, but some other statement which he mistook for it; or if we believed that the kind of statement in question was one with regard to which there was no presumption that, being in the Times, it would be true: in either of these cases we should, I think, feel that he had not answered our question. We should still doubt whether what he had said was true. We should still doubt whether he knew what he asserted; and since a man cannot tell you how he knows a thing unless he does know that thing, we should think that, though he might have told us truly how he came to believe it, he had certainly not told us how he knew it. But though we should thus hold that he had not told us how he knew what he had asserted, and that he had given us no reason for believing it to be true; we must yet admit that he had given us a reason in a sense—a bad reason, a reason which was no reason because it had no tendency to show that what he believed was true; and we might also be perfectly convinced that he had given us the reason why he believed it—the proposition by believing which he was induced also to believe his original assertion.

I mean, then, by my question, "How do we know that other people exist?" what, I believe, is ordinarily meant, namely, "What reason have we for believing that they exist?" and by this again I mean, what I also believe is ordinarily meant, namely, "What proposition do we believe, which is both true itself and is also such that it would not be true, unless other people existed?" And I hope it is plain that this question, thus explained, is quite a different question from the psychological question, which I said I did not mean to ask—from the question, "How does our belief in the existence of other people arise?" My illustration, I hope, has made this plain. For I have pointed out that we may quite well hold that a man has told us how a belief of his arises, and even what was the reason which made him adopt that belief, and yet may have failed to give us any good reason for his belief—any proposition which is both true itself, and also such that the truth of his belief follows from it. And, indeed, it is plain that if any one ever believes what is false, he is believing something for which there is no good reason, in the sense which I have explained, and for which, therefore, he cannot possibly have a good reason; and yet it plainly does not follow that his belief did not arise in anyway whatever, nor even that he had no reason for it—no bad reason. It is plain that false beliefs do arise in some way or other—they have origins and causes: and many people who hold them have bad reasons for holding them—their belief does arise (by inference or otherwise) from their belief in some other proposition, which is not itself true, or else is not a good reason for holding that, which they infer from it, or which, in some other way, it induces them to believe. I submit, therefore, that the question, "What good reason have we for believing in the existence of other people?" is different from the question, "How does that belief arise?" But when I say this, I must not be misunderstood; I must not be understood to affirm that the answer to both questions may not, in a sense, be the same. I fully admit that the very same fact, which suggests to us the belief in the existence of other people, may also be a good reason for believing that they do exist. All that I maintain is that the question whether it is a good reason for that belief is a different question from the question whether it suggests that belief: if we assert that a certain fact both suggests our belief in the existence of other persons and is also a good reason for holding that belief, we are asserting two different things and not one only. And hence, when I assert, as I shall assert, that we have a good reason for our belief in the existence of other persons, I must not be understood also to assert either that we infer the existence of other persons from this good reason, or that our belief in that good reason suggests our belief in the existence of other persons in any other way. It is plain, I think, that a man may believe two true propositions, of which the one would not be true, unless the other were true too, without, in any sense whatever, having arrived at his belief in the one from his belief in the other; and it is plain, at all events, that the question whether his belief in the one did arise from his belief in the other, is a different question from the question whether the truth of the one belief follows from the truth of the other.

I hope, then, that I have made it a little clearer what I mean by the question: "What reason have we for believing in the existence of other people?" and that what I mean by it is at all events different from what is meant by the question: "How does our belief in the existence of other people arise?"

But I am sorry to say that I have not yet reached the end of my explanations as to what my meaning is. I am afraid that the subject may seem very tedious. I can assure you that I have found it excessively tedious to try to make my meaning clear to myself. I have constantly found that I was confusing one question with another, and that, where I had thought I had a good reason for some assertion, I had in reality no good reason. But I may perhaps remind you that this question, "How do we know so and so?" "What reason have we for believing it?" is one of which philosophy is full; and one to which the most various answers have been given. Philosophy largely consists in giving reasons; and the question what are good reasons for a particular conclusion and what are bad, is one upon which philosophers have disagreed as much as on any other question. For one and the same conclusion different philosophers have given not only different, but incompatible, reasons; and conversely different philosophers have maintained that one and the same fact is a reason for incompatible conclusions. We are apt, I think, sometimes to pay too little attention to this fact. When we have taken, perhaps, no little pains to assure ourselves that our own reasoning is correct, and especially when we know that a great many other philosophers agree with us, we are apt to assume that the arguments of those philosophers, who have come to a contradictory conclusion, are scarcely worthy of serious consideration. And yet, I think, there is scarcely a single reasoned conclusion in philosophy, as to which we shall not find that some other philosopher, who has, so far as we know, bestowed equal pains on his reasoning, and with equal ability, has reached a conclusion incompatible with ours. We may be satisfied that we are right, and we may, in fact, be so; but it is certain that both cannot be right: either our opponent or we must have mistaken bad reasons for good. And this being so, however satisfied we may be that it is not we who have done so, I think we should at least draw the conclusion that it is by no means easy to avoid mistaking bad reasons for good; and that no process, however laborious, which is in the least likely to help us in avoiding this should be evaded. But it is at least possible that one source of error lies in mistaking one kind of reason for another—in supposing that, because there is, in one sense, a reason for a given conclusion, there is also a reason in another, or that because there is, in one sense, no reason for a given conclusion, there is, therefore, no reason at all. I believe myself that this is a very frequent source of error: but it is at least a possible one. And where, as disagreements show, there certainly is error on one side or the other, and reason, too, to suppose that the error is not easy to detect, I think we should spare no pains in investigating any source, from which it is even possible that the error may arise. For these reasons I think I am perhaps doing right in trying to explain as clearly as possible not only what reasons we have for believing in an external world, but also in what sense I take them to be reasons.

I proceed, then with my explanation. And there is one thing, which, I think my illustration has shown that I do not mean. I have defined a reason for a belief as a true proposition, which would not be true unless the belief itself—what is believed—were also true; and I have used, as synonymous with this form of words, the expressions: A reason for a belief is a true proposition from which the truth of the belief follows from which it could be validly inferred. Now these expressions might suggest the idea that I mean to restrict the word "reason," to what, in the strictest sense, might be called a logical reason—to propositions from which the belief in question follows, according to the rules of inference accepted by Formal Logic. But I am not using the words "follow," "validly inferred," in this narrow sense; I do not mean to restrict the words "reason for a belief" to propositions from which the laws of Formal Logic state that the belief could be deduced. The illustration which I gave is inconsistent with this restricted meaning. I said that the fact that a statement appeared in the Times might be a good reason for believing that that statement was true. And I am using the word "reason" in the wide and popular sense, in which it really might be. If, for instance, the Times stated that the King was dead, we should think that was a good reason for believing that the King was dead; we should think that the Times would not have made such a statement as that unless the King really were dead. We should, indeed, not think that the statement in the Times rendered it absolutely certain that the King was dead. But it is extremely unlikely that the Times would make a statement of this kind unless it were true; and, in that sense, the fact of the statement appearing in the Times would render it highly probable—much more likely than not—that the King was dead. And I wish it to be understood that I am using the words "reason for a belief" in this extremely wide sense. When I look for a good reason for our belief in the existence of other people, I shall not reject any proposition merely on the ground that it only renders their existence probable—only shows it to be more likely than not that they exist. Provided that the proposition in question does render it positively probable that they exist, then, if it also conforms to the conditions which I am about to mention, I shall call it a "good reason."

But it is not every proposition which renders it probable that other people exist, which I shall consider to be a good answer to my question. I have just explained that my meaning is wide in one direction—in admitting some propositions which render a belief merely probable; but I have now to explain that it is restricted in two other directions. I do mean to exclude certain propositions which do render that belief probable. When I ask: What reason have we for believing in the existence of other people? a certain ambiguity is introduced by the use of the plural "we." If each of several different persons has a reason for believing that he himself exists, then it is not merely probable, but certain, according to the rules of Formal Logic, that, in a sense, they "have a reason for believing" that several people exist; each has a reason for believing that he himself exists; and, therefore, all of them, taken together, have reasons for supposing that several persons exist. If, therefore, I were asking the question: What reason have we for believing in the existence of other persons? in this sense, it would follow that if each of us has a reason for believing in his own existence, these reasons, taken together, would be a reason for believing in the existence of all of us. But I am not asking the question in this sense: it is plain that this is not its natural sense. What I do mean to ask is: Does each single one of us know any proposition, which is a reason for believing that others exist? I am using "we," that is to say, in the sense of "each of us." But again I do mean each of us: I am not merely asking whether some one man knows a proposition which is a reason for believing that other men exist. It would be possible that some one man, or some few men, should know such a proposition, and yet the rest know no such proposition. But I am not asking whether this is the case. I am asking whether among propositions of the kind which (as we commonly suppose) all or almost all men know, there is any which is a reason for supposing that other men exist. And in asking this question I am not begging the question by supposing that all men do exist. My question might, I think, be put quite accurately as follows. There are certain kinds of belief which, as we commonly suppose, all or almost all men share. I describe this kind of belief as "our" beliefs, simply as an easy way of pointing out which kind of belief I mean, but without assuming that all men do share them. And I then ask: Supposing a single man to have beliefs of this kind, which among them would be a good reason for supposing that other men existed having like beliefs?

This, then, is the first restriction which I put upon the meaning of my question. And it is, I think, a restriction which, in their natural meaning, the words suggest. When we ask: What reason have we for believing that other people exist? we naturally understand that question to be equivalent to: What reason has each of us for that belief? And this question again is naturally equivalent to the question: Which among the propositions that a single man believes, but which are of the kind which (rightly or wrongly) we assume all men to believe, are such that they would not be true unless some other person than that man existed? But there is another restriction which, I think, the words of my question also naturally suggest. If we were to ask anyone the question: How do you know that you did see that statement in the Times? and he were to answer "Because I did see it in the Times and in the Standard too," we should not think that he had given us a reason for the belief that he saw it in the Times. We should not think his answer a reason, because it asserts the very thing for which we require a reason. And similarly when I ask: How do we know that any thing or person exists, other than ourselves and what we directly perceive? What reason have we for believing this? I must naturally be understood to mean: What proposition, other than one which itself asserts or presupposes the existence of something beyond ourselves and our own perceptions, is a reason for supposing that such a thing exists? And this restriction obviously excludes an immense number of propositions of a kind which all of us do believe. We all of us believe an immense number of different propositions about the existence of things which we do not directly perceive, and many of these propositions are, in my sense, good reasons for believing in the existence of still other things. The belief in the existence of a statement in the Times, when we have not seen that statement, may, as I implied, be a good reason for believing that someone is dead. But no such proposition can be a good answer to my question, because it asserts the very kind of thing for which I require a reason: it asserts the existence of something other than myself and what I directly perceive. When I am asking: What reason have I for believing in the existence of anything but myself, my own perceptions, and what I do directly perceive? you would naturally understand me to mean: What reason, other than the existence of such a thing, have I for this belief?

Each of us, then, we commonly assume, believes some true propositions, which do not themselves assert the existence of anything other than himself, his own perceptions, or what he directly perceives. Each of us, for instance, believes that he himself has and has had certain particular perceptions: and these propositions are propositions of the kind I mean—propositions which do not themselves assert the existence of anything other than himself, his own perceptions, and what he directly perceives: they are, I think, by no means the only propositions of this kind, which most of us believe: but they are propositions of this kind. But, as I say, I am not assuming that each of us—each of several different people—does believe propositions of this kind. All that I assume is that at least one man does believe some such propositions. And then I ask: Which among those true propositions, which one man believes, are such that they would probably not be true, unless some other man existed and had certain particular perceptions? Which among them are such that it follows (in the wide sense, which I have explained) from their truth, that it is more likely than not that some other man has perceptions? This is the meaning of my question, so far as I have hitherto explained it: and I hope this meaning is quite clear. It is in this sense that I am asking: What reason have we for believing that other people exist? How do we know that they exist? This, indeed, is not all that I mean by that question: there is one other point—the most important one—which remains to be explained. But this is part of what I mean to ask; and before I go on to explain what else I mean, I wish first to stop and enquire what is the answer to this part of my question. What is the answer to the question: Which among the true propositions, of a kind which (as we commonly assume) each of us believes, and which do not themselves assert the existence of anything other than that person himself, his own perceptions, or what he directly perceives, are such that they would probably not be true unless some other person existed, who had perceptions in some respects similar to his own?

Now to this question the answer is very obvious. It is very obvious that in this sense we have reasons for believing in the existence of other persons, and also what some of those reasons are. But I wish to make it quite plain that this is so: that in this sense one man has a reason for believing that another has certain perceptions. All that I am asking you to grant, is, you see, that some of you would not be having just those perceptions which you now have, unless I, as I read this paper, were perceiving more or less black marks on a more or less white ground; or that I on the other hand, should not be having just those perceptions which I now have, unless some other persons than myself were hearing the sounds of my voice. And I am not asking you even to grant that this is certain—only that it is positively probable—more likely than not. Surely it is very obvious that this proposition is true. But I wish to make it quite clear what would be the consequences of denying that any such propositions are true—propositions which assert that the existence of certain perceptions in one man are a reason for believing in the existence of certain perceptions in another man—which assert that one man would probably not have had just those perceptions which he did have, unless some other man had had certain particular perceptions. It is plain, I think, that, unless some such propositions are true, we have no more reason for supposing that Alexander the Great ever saw an elephant, than for supposing that Sindbad the Sailor saw a Roc; we have no more reason for supposing that anybody saw Julius Caesar murdered in the Senate House at Rome, than for supposing that somebody saw him carried up to Heaven in a fiery chariot. It is plain, I think, that if we have any reason at all for supposing that in all probability Alexander the Great did see an elephant, and that in all probability no such person as Sindbad the Sailor ever saw a Roc, part of that reason consists in the assumption that some other person would probably not have had just those perceptions which he did have, unless Alexander the Great had seen an elephant, and unless Sindbad the Sailor had not seen a Roc. And most philosophers, I think, are willing to admit that we have some reason, in some sense or other, for such propositions as these. They are willing to admit not only that some persons probably did see Julius Caesar murdered in the Senate House; but also that some persons, other than those who saw it, had and have some reason for supposing that some one else probably saw it. Some sceptical philosophers might, indeed, deny both propositions; and to refute their views, I admit, other arguments are needed than any which I shall bring forward in this paper. But most philosophers will, I think, admit not only that facts, for which there is, as we say, good historical evidence, are probably true; but also that what we call good historical evidence really is in some sense a good reason for thinking them true. Accordingly I am going to assume that many propositions of the following kind are true. Propositions, namely, which assert that one man would probably not have certain perceptions which he does have, unless some other man had certain particular perceptions. That some of you, for instance, would probably not be having precisely the perceptions which you are having, unless I were having the perception of more or less black marks on a more or less white ground. And, in this sense, I say, we certainly have reasons for supposing that other people have perceptions similar, in some respects, to those which we sometimes have.