Chapter II. The Existence of Matter

by Bertrand Russell

　　In this chapter we have to ask ourselves whether, in any sense at all,there is such a thing as matter. Is there a table which has a certainintrinsic nature, and continues to exist when I am not looking, or is thetable merely a product of my imagination, a dream-table in a veryprolonged dream? This question is of the greatest importance. For if wecannot be sure of the independent existence of objects, we cannot be sureof the independent existence of other people's bodies, and therefore stillless of other people's minds, since we have no grounds for believing intheir minds except such as are derived from observing their bodies. Thusif we cannot be sure of the independent existence of objects, we shall beleft alone in a desert—it may be that the whole outer world isnothing but a dream, and that we alone exist. This is an uncomfortablepossibility; but although it cannot be strictly proved to be false, thereis not the slightest reason to suppose that it is true. In this chapter wehave to see why this is the case.

　　Before we embark upon doubtful matters, let us try to find some more orless fixed point from which to start. Although we are doubting thephysical existence of the table, we are not doubting the existence of thesense-data which made us think there was a table; we are not doubtingthat, while we look, a certain colour and shape appear to us, and while wepress, a certain sensation of hardness is experienced by us. All this,which is psychological, we are not calling in question. In fact, whateverelse may be doubtful, some at least of our immediate experiences seemabsolutely certain.

　　Descartes (1596-1650), the founder of modern philosophy, invented a methodwhich may still be used with profit—the method of systematic doubt.He determined that he would believe nothing which he did not see quiteclearly and distinctly to be true. Whatever he could bring himself todoubt, he would doubt, until he saw reason for not doubting it. Byapplying this method he gradually became convinced that the only existenceof which he could be quite certain was his own. He imagined adeceitful demon, who presented unreal things to his senses in a perpetualphantasmagoria; it might be very improbable that such a demon existed, butstill it was possible, and therefore doubt concerning things perceived bythe senses was possible.

　　But doubt concerning his own existence was not possible, for if he did notexist, no demon could deceive him. If he doubted, he must exist; if he hadany experiences whatever, he must exist. Thus his own existence was anabsolute certainty to him. 'I think, therefore I am,' he said (Cogito,ergo sum); and on the basis of this certainty he set to work to buildup again the world of knowledge which his doubt had laid in ruins. Byinventing the method of doubt, and by showing that subjective things arethe most certain, Descartes performed a great service to philosophy, andone which makes him still useful to all students of the subject.

　　But some care is needed in using Descartes' argument. 'I think, thereforeI am' says rather more than is strictly certain. It might seem as thoughwe were quite sure of being the same person to-day as we were yesterday,and this is no doubt true in some sense. But the real Self is as hard toarrive at as the real table, and does not seem to have that absolute,convincing certainty that belongs to particular experiences. When I lookat my table and see a certain brown colour, what is quite certain at onceis not 'I am seeing a brown colour', but rather, 'a brown colour isbeing seen'. This of course involves something (or somebody) which (orwho) sees the brown colour; but it does not of itself involve that more orless permanent person whom we call 'I'. So far as immediate certaintygoes, it might be that the something which sees the brown colour is quitemomentary, and not the same as the something which has some differentexperience the next moment.

　　Thus it is our particular thoughts and feelings that have primitivecertainty. And this applies to dreams and hallucinations as well as tonormal perceptions: when we dream or see a ghost, we certainly do have thesensations we think we have, but for various reasons it is held that nophysical object corresponds to these sensations. Thus the certainty of ourknowledge of our own experiences does not have to be limited in any way toallow for exceptional cases. Here, therefore, we have, for what it isworth, a solid basis from which to begin our pursuit of knowledge.

　　The problem we have to consider is this: Granted that we are certain ofour own sense-data, have we any reason for regarding them as signs of theexistence of something else, which we can call the physical object? Whenwe have enumerated all the sense-data which we should naturally regard asconnected with the table, have we said all there is to say about thetable, or is there still something else—something not a sense-datum,something which persists when we go out of the room? Common senseunhesitatingly answers that there is. What can be bought and sold andpushed about and have a cloth laid on it, and so on, cannot be a merecollection of sense-data. If the cloth completely hides the table, weshall derive no sense-data from the table, and therefore, if the tablewere merely sense-data, it would have ceased to exist, and the cloth wouldbe suspended in empty air, resting, by a miracle, in the place where thetable formerly was. This seems plainly absurd; but whoever wishes tobecome a philosopher must learn not to be frightened by absurdities.

　　One great reason why it is felt that we must secure a physical object inaddition to the sense-data, is that we want the same object for differentpeople. When ten people are sitting round a dinner-table, it seemspreposterous to maintain that they are not seeing the same tablecloth, thesame knives and forks and spoons and glasses. But the sense-data areprivate to each separate person; what is immediately present to the sightof one is not immediately present to the sight of another: they all seethings from slightly different points of view, and therefore see themslightly differently. Thus, if there are to be public neutral objects,which can be in some sense known to many different people, there must besomething over and above the private and particular sense-data whichappear to various people. What reason, then, have we for believing thatthere are such public neutral objects?

　　The first answer that naturally occurs to one is that, although differentpeople may see the table slightly differently, still they all see more orless similar things when they look at the table, and the variations inwhat they see follow the laws of perspective and reflection of light, sothat it is easy to arrive at a permanent object underlying all thedifferent people's sense-data. I bought my table from the former occupantof my room; I could not buy his sense-data, which died when he wentaway, but I could and did buy the confident expectation of more or lesssimilar sense-data. Thus it is the fact that different people have similarsense-data, and that one person in a given place at different times hassimilar sense-data, which makes us suppose that over and above thesense-data there is a permanent public object which underlies or causesthe sense-data of various people at various times.

　　Now in so far as the above considerations depend upon supposing that thereare other people besides ourselves, they beg the very question at issue.Other people are represented to me by certain sense-data, such as thesight of them or the sound of their voices, and if I had no reason tobelieve that there were physical objects independent of my sense-data, Ishould have no reason to believe that other people exist except as part ofmy dream. Thus, when we are trying to show that there must be objectsindependent of our own sense-data, we cannot appeal to the testimony ofother people, since this testimony itself consists of sense-data, and doesnot reveal other people's experiences unless our own sense-data are signsof things existing independently of us. We must therefore, if possible,find, in our own purely private experiences, characteristics which show,or tend to show, that there are in the world things other than ourselvesand our private experiences.

　　In one sense it must be admitted that we can never prove the existence ofthings other than ourselves and our experiences. No logical absurdityresults from the hypothesis that the world consists of myself and mythoughts and feelings and sensations, and that everything else is merefancy. In dreams a very complicated world may seem to be present, and yeton waking we find it was a delusion; that is to say, we find that thesense-data in the dream do not appear to have corresponded with suchphysical objects as we should naturally infer from our sense-data. (It istrue that, when the physical world is assumed, it is possible to findphysical causes for the sense-data in dreams: a door banging, forinstance, may cause us to dream of a naval engagement. But although, inthis case, there is a physical cause for the sense-data, there is not aphysical object corresponding to the sense-data in the way in which anactual naval battle would correspond.) There is no logical impossibilityin the supposition that the whole of life is a dream, in which weourselves create all the objects that come before us. But although this isnot logically impossible, there is no reason whatever to suppose that itis true; and it is, in fact, a less simple hypothesis, viewed as a meansof accounting for the facts of our own life, than the common-sensehypothesis that there really are objects independent of us, whose actionon us causes our sensations.

　　The way in which simplicity comes in from supposing that there really arephysical objects is easily seen. If the cat appears at one moment in onepart of the room, and at another in another part, it is natural to supposethat it has moved from the one to the other, passing over a series ofintermediate positions. But if it is merely a set of sense-data, it cannothave ever been in any place where I did not see it; thus we shall have tosuppose that it did not exist at all while I was not looking, but suddenlysprang into being in a new place. If the cat exists whether I see it ornot, we can understand from our own experience how it gets hungry betweenone meal and the next; but if it does not exist when I am not seeing it,it seems odd that appetite should grow during non-existence as fast asduring existence. And if the cat consists only of sense-data, it cannot behungry, since no hunger but my own can be a sense-datum to me. Thus thebehaviour of the sense-data which represent the cat to me, though it seemsquite natural when regarded as an expression of hunger, becomes utterlyinexplicable when regarded as mere movements and changes of patches ofcolour, which are as incapable of hunger as a triangle is of playingfootball.

　　But the difficulty in the case of the cat is nothing compared to thedifficulty in the case of human beings. When human beings speak—thatis, when we hear certain noises which we associate with ideas, andsimultaneously see certain motions of lips and expressions of face—itis very difficult to suppose that what we hear is not the expression of athought, as we know it would be if we emitted the same sounds. Of coursesimilar things happen in dreams, where we are mistaken as to the existenceof other people. But dreams are more or less suggested by what we callwaking life, and are capable of being more or less accounted for onscientific principles if we assume that there really is a physical world.Thus every principle of simplicity urges us to adopt the natural view,that there really are objects other than ourselves and our sense-datawhich have an existence not dependent upon our perceiving them.

　　Of course it is not by argument that we originally come by our belief inan independent external world. We find this belief ready in ourselves assoon as we begin to reflect: it is what may be called an instinctivebelief. We should never have been led to question this belief but for thefact that, at any rate in the case of sight, it seems as if thesense-datum itself were instinctively believed to be the independentobject, whereas argument shows that the object cannot be identical withthe sense-datum. This discovery, however—which is not at allparadoxical in the case of taste and smell and sound, and only slightly soin the case of touch—leaves undiminished our instinctive belief thatthere are objects corresponding to our sense-data. Sincethis belief does not lead to any difficulties, but on the contrary tendsto simplify and systematize our account of our experiences, there seems nogood reason for rejecting it. We may therefore admit—though with aslight doubt derived from dreams—that the external world does reallyexist, and is not wholly dependent for its existence upon our continuingto perceive it.

　　The argument which has led us to this conclusion is doubtless less strongthan we could wish, but it is typical of many philosophical arguments, andit is therefore worth while to consider briefly its general character andvalidity. All knowledge, we find, must be built up upon our instinctivebeliefs, and if these are rejected, nothing is left. But among ourinstinctive beliefs some are much stronger than others, while many have,by habit and association, become entangled with other beliefs, not reallyinstinctive, but falsely supposed to be part of what is believedinstinctively.

　　Philosophy should show us the hierarchy of our instinctive beliefs,beginning with those we hold most strongly, and presenting each as muchisolated and as free from irrelevant additions as possible. It should takecare to show that, in the form in which they are finally set forth, ourinstinctive beliefs do not clash, but form a harmonious system. There cannever be any reason for rejecting one instinctive belief except that itclashes with others; thus, if they are found to harmonize, the wholesystem becomes worthy of acceptance.

　　It is of course possible that all or any of our beliefs may bemistaken, and therefore all ought to be held with at least some slightelement of doubt. But we cannot have reason to reject a beliefexcept on the ground of some other belief. Hence, by organizing ourinstinctive beliefs and their consequences, by considering which amongthem is most possible, if necessary, to modify or abandon, we can arrive,on the basis of accepting as our sole data what we instinctively believe,at an orderly systematic organization of our knowledge, in which, thoughthe possibility of error remains, its likelihood is diminished bythe interrelation of the parts and by the critical scrutiny which haspreceded acquiescence.

　　This function, at least, philosophy can perform. Most philosophers,rightly or wrongly, believe that philosophy can do much more than this—thatit can give us knowledge, not otherwise attainable, concerning theuniverse as a whole, and concerning the nature of ultimate reality.Whether this be the case or not, the more modest function we have spokenof can certainly be performed by philosophy, and certainly suffices, forthose who have once begun to doubt the adequacy of common sense, tojustify the arduous and difficult labours that philosophical problemsinvolve.