Philosophical Studies · G. E. Moore
THE NATURE AND REALITY OF OBJECTS OF PERCEPTION
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.
But when I said I was going to ask the question: What reason have we for supposing that other people exist? you will certainly not have thought that I merely meant to ask the question which I have just answered. My words will have suggested to you something much more important than merely this. When, for instance, I said that to the question "How do you know that?" the answer "I saw it in the _Times"_ would be a satisfactory answer, you may have felt, as I felt, that it would not in all circumstances be regarded as such. The person who asked the question might, in some cases, fairly reply: "That is no answer: how do you know that, because you saw a thing in the _Times_, it is therefore true?" In other words he might ask fora _reason_ for supposing that the occurrence of a particular statement in the _Times_ was a reason for supposing that statement true. And this is a question to which we all believe that there may be an answer. We believe that, with some kinds of statements which the _Times_ makes--some kinds of statements with regard to Fiscal Policy for example--the fact that the _Times_ makes them is no reason for supposing them to be true: whereas with regard to other kinds of statements, which it makes, such a statement, for instance, as that the King was dead, the fact that it makes them _is_ a reason for supposing them true. We believe that there are some kinds of statements, which it is very unlikely the _Times_ would make, unless they were true; and others which it is not at all unlikely that the _Times_ might make, although they were not true. And we believe that a reason might be given for distinguishing, in this way, between the two different kinds of statement: for thinking that, in some cases (on points, for instance, which, as we should say, are not simple questions of fact) the _Times_ is fallible, whereas in other cases, it is, though not absolutely infallible, very unlikely to state what is not true.
Now it is precisely in this further sense that I wish to consider: what reason have we for believing that certain particular things, other than ourselves, our own perceptions, and what we directly perceive, are real? I have asserted that I do have certain perceptions, which it is very unlikely I should have, unless some other person had certain particular perceptions; that, for instance, it is very unlikely I should be having precisely those perceptions which I am now having unless someone else were hearing the sound of my voice. And I now wish to ask: What reason have I for supposing that this is unlikely? What reason has any of us for supposing that any such proposition is true? And I mean by "having a reason" precisely what I formerly meant. I mean: What other proposition do I know, which would not be true, unless my perception were connected with someone else's perception, in the manner in which I asserted them to be connected? Here again I am asking for _a good reason_; and am not asking a psychological question with regard to origin. Here again I am not asking for a reason, in the strict sense of Formal Logic; I am merely asking for a proposition which would probably not be true, unless what I asserted were true. Here again I am asking for some proposition of a kind which _each_ of us believes; I am asking: What reason has _each_ of us for believing that some of his perceptions are connected with particular perceptions of other people in the manner I asserted?--for believing that he would not have certain perceptions that he does have, unless some other person had certain particular perceptions? And here again I am asking for a _reason_--I am asking for some proposition _other_ than one which itself asserts: When one man has a perception of such and such a particular kind, it _is_ probable that another man has a perception or thought of this or that other kind.
But what kind of reason can be given for believing a proposition of this sort? For believing a proposition which asserts that, since one particular thing exists, it is probable that another particular thing also exists? One thing I think is plain, namely that we can have no good reason for believing such a proposition, unless we have good reason for believing some _generalisation._ It is commonly believed, for instance, that certain so-called flint arrow-heads, which have been discovered, were probably made by prehistoric men; and I think it is plain that we have no reason for believing this unless we have reason to suppose that objects which resemble these in certain particular respects are _generally_ made by men--are _more often_ made by men than by any other agency. Unless certain particular characteristics which those arrow-heads have were characteristics which belonged at least more frequently to articles of human manufacture than to any articles not made by men, it would surely be just as likely as not that these arrowheads were _not_ made by men--that they were, in fact not arrow-heads.
That is to say, unless we have reason to assert a _generalisation_--the generalisation that objects of a certain kind are _generally_ made by men, we have no reason to suppose that these particular objects, which are of the kind in question, _were_ made by men. And the same, so far as I can see, is true universally. If we ever have any reason for asserting that, since one particular thing exists, another probably exists or existed or will exist also part of our reason, at least, must consist in reasons for asserting some generalisation--for asserting that the existence of things of a particular kind is, more often than not, accompanied or preceded or followed by the existence of things of another particular kind. It is, I think, sometimes assumed that an alternative to this theory may be found in the theory that the existence of one kind of thing "intrinsically points to," or is "intrinsically a sign or symbol of" the existence of another thing. It is suggested that when a thing which thus points to the existence of another thing exists, then it is at least probable that the thing "pointed to" exists also. But this theory, I think, offers no real alternative.
For, in the first place, when we say that the existence of one thing A is a "sign of" or "points to" the existence of another thing B, we very commonly actually mean to say that when a thing like A exists, a thing like B _generally_ exists too. We may, no doubt, mean something else _too_; but this we do mean. We say, for instance, that certain particular words, which we hear or read, are a "sign" that somebody has thought of the particular things which we call the meaning of those words. But we should certainly hesitate to admit that the hearing or reading of certain words could be called a "sign" of the existence of certain thoughts, unless it were true that when those words are heard or read, the thoughts in question _generally_ have existed. If when those words were heard or read, the thoughts had generally _not_ existed, we should say that, in one sense of the word at all events, the hearing of the words was _not_ a sign of the existence of the thoughts. In this sense, therefore, to say that the existence of A "points to" or "is a sign of" the existence of B is actually to say that when A exists, B _generally_ exists also.
But, no doubt, the words "points to" "is a sign of" may be used in some other sense: they may, for instance, mean only that the existence of A _suggests_ in some way the belief that B exists. And in such a case we certainly might know that the existence of A pointed to the existence of B, without knowing that when A existed B generally existed also. Let us suppose, then, that in some such sense A does "point to" the existence of B; can this fact give us a reason for supposing it even probable that B existed. Certainly it can, _provided_ it is true that when A _does_ point to the existence of B, B _generally_ exists. But surely it can do so, only on this condition. If when A _points_ to the existence of B, B, nevertheless, does _not_ generally exist, then surely the fact that A points to the existence of B can constitute no probability that B does not exist: on the contrary it will then be probable that, even though A "points to" the existence of B, B does _not_ exist. We have, in fact, only substituted the generalisation that A's _pointing to_ B is generally accompanied by the existence of B, for the generalisation that A's _existence_ is generally accompanied by the existence of B. If we are to have any reason for asserting that, when A _points to_ or is a sign of the existence of B, B probably exists, we must still have a reason for some generalisation--for a generalisation which asserts that when one thing points to the existence of another, that other _generally_ exists.
It is plain, then, I think, that if we are to find a reason for the assertion that some particular perception of mine would probably not exist, unless someone else were having or had had a perception of a kind which I can name, we must find a reason for _some_ generalisation. And it is also plain, I think, that in many cases of this kind the generalisation must consist in an assertion that when one man has a certain kind of perception, some other man generally has had some other perception or belief. We assume, for instance, that when we hear or read certain words, somebody besides ourselves has thought the thoughts, which constitute the meaning of those words; and it is plain, I think, that we have no reason for this assumption except one which is also a reason for the assumption that when certain words are heard or read, somebody generally has had certain thoughts. And my enquiry, therefore, at least includes the enquiry: What reasons have we for such generalisations as these? for generalisations which assert a connection between the existence of a certain kind of perception in one man, and that of a certain kind of perception or belief in another man?
And to this question, I think, but one answer can be given. If we have any reason for such generalisations at all, some reason must be given, in one way or another, by observation--by observation, understood in the wide sense in which it includes "experiment." No philosopher, I think, has ever failed to assume that observation does give a reason for _some_ generalisations--for some propositions which assert that when one kind of thing exists, another generally exists or has existed in a certain relation to it. Even those who, like Hume, imply that observation cannot give a _reason_ for anything, yet constantly appeal to observation in support of generalisations of their own. And even those who hold that observation can give no reason for any generalisation about the relation of one man's perceptions to another's, yet hold that it _can_ give a reason for generalisations about the relation of some to others among a man's own perceptions. It is, indeed, by no means agreed _how_ observation can give a reason for any generalisation. Nobody knows what reason we have, if we have any, for supposing that it can. But _that_ it can, everyone, I think, assumes. I think, therefore, most philosophers will agree, that if we can find any reason at all for generalisations of the kind in which I am interested, a reason for _some_ of them at all events must be found in observation. And what I propose to ask is: What reason can be found in observation for even a single proposition of the kind I have described? for a proposition which asserts that when one man has one kind of perception, another man generally has or has had another.
But, when it is said that observation gives us a reason for generalisations, two things may be meant neither of which I mean. In the first place, we popularly use "observation" in a sense in which we can be said to _observe_ the perceptions, feelings and thoughts of other people: in which, therefore, we can be said to observe the very things with regard to which I am asking what reason we have for believing in their existence. But it is universally[1] agreed that there is a sense in which no man can observe the perceptions, feelings or thoughts of any other man. And it is to this strict sense that I propose to confine the word. I shall use it in a sense, in which we can certainly be said to observe nothing but ourselves, our own perceptions, thoughts and feelings, and what we directly perceive. And in the second place, it may be said that observations made by another person may give _me_ a reason for believing some generalisation.
And it is certainly the case that for many of the generalisations in which we all believe, if we have a reason in observation at all, it is not in _our own_ observation that we have it: part of our reason, at all events, lies in things which _other_ people have observed but which we ourselves have not observed. But in asking this particular question, I am not asking for reasons of this sort. The very question that I am asking is: What reason has any one of us for supposing that any other person whatever has ever made any observations? And just as, in the first meaning which I gave to this question, it meant: What thing, that any single man observes is such that it would probably not have existed, unless some other man had made a particular observation? So now I am asking: Which among the things, which _one single man observes_, are such that they would probably not have existed, unless it were true that some of them generally stood in certain relations to observations of some other person? I am asking: Which among _my own_ observations give me a reason for supposing that some of them are of a kind which are generally preceded or accompanied by observations of other people?
Which, for instance, among my own observations give a good reason for the generalisation that when I hear certain words, somebody else has generally had certain particular thoughts, or that whenever anyone hears certain words, somebody else has generally had the thoughts which constitute what we call the meaning of those words? I am asking: Which among the vast series of observations, which any one individual makes during his lifetime, give a good reason for any generalisation _whatever_ of this kind--a generalisation which asserts that some of them are generally preceded by certain thoughts, perceptions or feelings in other persons? I quite admit that there are some generalisations of this kind for which the observations of _some_ particular men will _not_ give a reason. All that I ask is: Is there even _one_ generalisation of this kind, for which the kind of observations, which (as we commonly assume) each man, or nearly every man does make, do give a reason? Among observations of the kind which (as we commonly assume) are common to you and to me, do yours, by themselves, give any reason for even _one_ such generalisation? And do mine, by themselves, give any reason for even _one_ such generalisation? And if they do, which, among these observations, is it which do so?
My question is, then: What reason do my own observations give me, for supposing that any perception whatever, which I have, would probably not occur, unless some other person had a certain kind of perception? What reason do my own observations give me for supposing, for instance, that I should not be perceiving what I do now perceive, unless someone were hearing the sound of my voice? What reason do your own observations give you for supposing that you would not be perceiving just what you are perceiving, unless I were perceiving more or less black marks on a more or less white ground? The question does, I think, appear to be a reasonable one; and most philosophers, I think, have assumed that there is an answer to it. Yet it may be said that there is no answer to it: that my own observations give me no reason whatever for any single proposition of this kind. There are certain philosophers (even apart from thorough sceptics, with whom, as I have said, I am not now arguing) who have denied that they do.
Ideas discussed in this chapter
Text from Project Gutenberg, public domain in the United States.