The Existence of Matter

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 certain intrinsic nature, and continues to exist when I am not looking, or is the table merely a product of my imagination, a dream-table in a very prolonged dream? This question is of the greatest importance. For if we cannot be sure of the independent existence of objects, we cannot be sure of the independent existence of other people's bodies, and therefore still less of other people's minds, since we have no grounds for believing in their minds except such as are derived from observing their bodies. Thus if we cannot be sure of the independent existence of objects, we shall be left alone in a desert—it may be that the whole outer world is nothing but a dream, and that we alone exist. This is an uncomfortable possibility; but although it cannot be strictly proved to be false, there is not the slightest reason to suppose that it is true. In this chapter we have to see why this is the case.

In this chapter, we must ask whether matter exists in any sense at all. Is there a table with a nature of its own that continues to exist when I am not looking? Or is the table merely a product of my imagination, a dream-table in a very long dream? This question is extremely important. For if we cannot be sure that objects exist independently of us, neither can we be sure about other people's bodies. And we can be even less sure that other people's minds exist independently of us. After all, our only grounds for believing in their minds come from observing their bodies. So if we cannot be sure that objects exist independently of us, we are left alone in a desert. The whole outside world may be nothing but a dream, and we alone may exist. This possibility is uncomfortable. But although we cannot prove with complete certainty that this possibility is false, there is no reason whatsoever to think it is true. In this chapter, we must see why there is no such reason.

Before we embark upon doubtful matters, let us try to find some more or less fixed point from which to start. Although we are doubting the physical existence of the table, we are not doubting the existence of the sense-data which made us think there was a table; we are not doubting that, while we look, a certain colour and shape appear to us, and while we press, a certain sensation of hardness is experienced by us. All this, which is psychological, we are not calling in question. In fact, whatever else may be doubtful, some at least of our immediate experiences seem absolutely certain.

Before we explore doubtful questions, let us try to find a reasonably firm starting point. Although we doubt the table’s physical existence, we do not doubt the sense-data that made us think a table existed. We do not doubt that, while we look, a certain colour and shape appear to us. Nor do we doubt that, while we press, we experience a certain feeling of hardness. We are not questioning any of these psychological experiences. In fact, whatever else may be doubtful, at least some of our immediate experiences seem absolutely certain.

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

Descartes (1596-1650), the founder of modern philosophy, developed a method that may still be useful: systematic doubt. He decided to believe nothing unless he saw clearly and distinctly that it was true. He would doubt anything he could bring himself to doubt, until he found a reason not to doubt it. By using this method, he gradually became convinced that he could be quite certain only of his own existence. He imagined a deceitful demon that presented unreal things to his senses in an endless series of shifting illusions. Such a demon might be very unlikely to exist, but its existence was still possible. So it was possible to doubt the things he perceived through his senses.

But doubt concerning his own existence was not possible, for if he did not exist, no demon could deceive him. If he doubted, he must exist; if he had any experiences whatever, he must exist. Thus his own existence was an absolute 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 build up again the world of knowledge which his doubt had laid in ruins. By inventing the method of doubt, and by showing that subjective things are the most certain, Descartes performed a great service to philosophy, and one which makes him still useful to all students of the subject.

But he could not doubt his own existence, because if he did not exist, no demon could deceive him. If he doubted, he must exist. If he had any experiences at all, he must exist. So his own existence was absolutely certain to him. 'I think, therefore I am,' he said (Cogito, ergo sum). On the basis of this certainty, he began rebuilding the world of knowledge his doubt had left in ruins. Descartes invented the method of doubt and showed that subjective things are the most certain. In doing so, he made a great contribution to philosophy, one that remains useful to all students of the subject.

But some care is needed in using Descartes' argument. 'I think, therefore I am' says rather more than is strictly certain. It might seem as though we 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 to arrive at as the real table, and does not seem to have that absolute, convincing certainty that belongs to particular experiences. When I look at my table and see a certain brown colour, what is quite certain at once is not 'I am seeing a brown colour', but rather, 'a brown colour is being seen'. This of course involves something (or somebody) which (or who) sees the brown colour; but it does not of itself involve that more or less permanent person whom we call 'I'. So far as immediate certainty goes, it might be that the something which sees the brown colour is quite momentary, and not the same as the something which has some different experience the next moment.

But we need to be careful when using Descartes' argument. 'I think, therefore I am' says a little more than we can be strictly certain of. We might seem quite sure that we are the same person today as yesterday. And in some sense, we undoubtedly are. But the real Self is as hard to establish as the real table. It does not seem to have the absolute, convincing certainty of particular experiences. When I look at my table and see a certain brown colour, what is immediately certain? Not 'I am seeing a brown colour', but rather, 'a brown colour is being seen'. Of course, seeing a brown colour involves something (or somebody) that sees it. But seeing alone does not imply the more or less permanent person we call 'I'. As far as immediate certainty goes, the something that sees the brown colour might exist only for a moment. It might not be the same as the something that has a different experience the next moment.

Thus it is our particular thoughts and feelings that have primitive certainty. And this applies to dreams and hallucinations as well as to normal perceptions: when we dream or see a ghost, we certainly do have the sensations we think we have, but for various reasons it is held that no physical object corresponds to these sensations. Thus the certainty of our knowledge of our own experiences does not have to be limited in any way to allow for exceptional cases. Here, therefore, we have, for what it is worth, a solid basis from which to begin our pursuit of knowledge.

So our own particular thoughts and feelings are what we can be certain of at the most basic level. The same certainty applies to dreams and hallucinations as to normal perceptions. When we dream or see a ghost, we certainly have the sensations we think we have. But for various reasons, people believe that no physical object corresponds to those sensations. So our certainty about our own experiences needs no limits to account for exceptional cases. We therefore have a solid starting point for our search for knowledge, for what that is worth.

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

Here is the problem we must consider: We are certain of our own sense-data. But do we have any reason to see them as signs that something else exists, something we can call the physical object? Suppose we list all the sense-data we would naturally connect with the table. Have we then said everything there is to say about the table? Or is there something more, something that is not a sense-datum and continues to exist when we leave the room? Common sense answers without hesitation that there is. Something we can buy, sell, push around, cover with a cloth, and so on cannot be a mere collection of sense-data. If the cloth completely hides the table, we receive no sense-data from the table. So if the table were merely sense-data, the table would have ceased to exist. The cloth would then hang in empty air, miraculously resting where the table used to be. This conclusion seems plainly absurd. But anyone who wants to become a philosopher must learn not to be frightened by absurdities.

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

One major reason we feel we must establish a physical object beyond sense-data is that different people need to share the same object. When ten people sit around a dinner table, saying they do not see the same tablecloth seems absurd. The same goes for the knives, forks, spoons, and glasses. But sense-data are private to each person. What one person sees directly is not what another person sees directly. All ten people see things from slightly different viewpoints, so all see things slightly differently. So, if there are to be shared objects independent of any one person's viewpoint, something beyond private sense-data must exist. Such objects could, in some sense, be known to many different people. They must therefore be more than the private, individual sense-data that appear to different people. What reason, then, do we have to believe that such shared, independent objects exist?

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

The first answer that naturally comes to mind is this. Although different people may see the table slightly differently, they all see more or less similar things. The differences in what they see follow the laws of perspective and light reflection. So it is easy to identify a lasting object underlying everyone’s different sense-data. I bought my table from the person who previously occupied my room. I could not buy his sense-data, which ceased to exist when he left. But I could and did buy the confident expectation of more or less similar sense-data. So different people have similar sense-data, and one person in the same place has similar sense-data at different times. These similarities lead us to suppose that something exists beyond the sense-data: a lasting object shared by everyone. This object underlies or causes the sense-data of different people at different times.

Now in so far as the above considerations depend upon supposing that there are other people besides ourselves, they beg the very question at issue. Other people are represented to me by certain sense-data, such as the sight of them or the sound of their voices, and if I had no reason to believe that there were physical objects independent of my sense-data, I should have no reason to believe that other people exist except as part of my dream. Thus, when we are trying to show that there must be objects independent of our own sense-data, we cannot appeal to the testimony of other people, since this testimony itself consists of sense-data, and does not reveal other people's experiences unless our own sense-data are signs of 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 ourselves and our private experiences.

To the extent that the arguments above assume that other people exist besides ourselves, they assume what needs proving. I perceive other people through certain sense-data, such as the sight of them or the sound of their voices. Suppose I had no reason to believe in physical objects independent of my sense-data. Then I would have no reason to believe that other people exist except as part of my dream. So, when trying to show that objects must exist independently of our own sense-data, we cannot rely on others' testimony. Their testimony itself consists of sense-data. Such testimony reveals nothing about other people's experiences unless our sense-data are signs of things existing independently of us. We must therefore look, if possible, within our own purely private experiences. We must find features that show, or tend to show, that the world contains things beyond ourselves and our private experiences.

In one sense it must be admitted that we can never prove the existence of things other than ourselves and our experiences. No logical absurdity results from the hypothesis that the world consists of myself and my thoughts and feelings and sensations, and that everything else is mere fancy. In dreams a very complicated world may seem to be present, and yet on waking we find it was a delusion; that is to say, we find that the sense-data in the dream do not appear to have corresponded with such physical objects as we should naturally infer from our sense-data. (It is true that, when the physical world is assumed, it is possible to find physical causes for the sense-data in dreams: a door banging, for instance, may cause us to dream of a naval engagement. But although, in this case, there is a physical cause for the sense-data, there is not a physical object corresponding to the sense-data in the way in which an actual naval battle would correspond.) There is no logical impossibility in the supposition that the whole of life is a dream, in which we ourselves create all the objects that come before us. But although this is not logically impossible, there is no reason whatever to suppose that it is true; and it is, in fact, a less simple hypothesis, viewed as a means of accounting for the facts of our own life, than the common-sense hypothesis that there really are objects independent of us, whose action on us causes our sensations.

In one sense, we must admit that we can never prove anything exists beyond ourselves and our experiences. There is no logical contradiction in supposing that the world consists only of me and my thoughts, feelings, and sensations. Everything else could be imaginary. In dreams, a very complicated world may seem to exist. Yet when we wake, we find that the dream world was an illusion. In other words, the sense-data in the dream do not seem to have matched physical objects. These are the objects we would naturally infer from what we experienced in the dream. (If we assume the physical world exists, we can indeed find physical causes for the sense-data in dreams. A banging door, for example, may cause us to dream of a naval battle. But although these sense-data have a physical cause, no physical object matches them as an actual naval battle would.) There is no logical impossibility in supposing that all of life is a dream. In such a dream, we ourselves create all the objects we encounter. But although this possibility involves no logical contradiction, there is no reason at all to suppose it is true. In fact, as an explanation of the facts of our lives, this theory is less simple than the common-sense theory. The common-sense theory holds that objects really exist independently of us, and their effects on us cause our sensations.

The way in which simplicity comes in from supposing that there really are physical objects is easily seen. If the cat appears at one moment in one part of the room, and at another in another part, it is natural to suppose that it has moved from the one to the other, passing over a series of intermediate positions. But if it is merely a set of sense-data, it cannot have ever been in any place where I did not see it; thus we shall have to suppose that it did not exist at all while I was not looking, but suddenly sprang into being in a new place. If the cat exists whether I see it or not, we can understand from our own experience how it gets hungry between one 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 as during existence. And if the cat consists only of sense-data, it cannot be hungry, since no hunger but my own can be a sense-datum to me. Thus the behaviour of the sense-data which represent the cat to me, though it seems quite natural when regarded as an expression of hunger, becomes utterly inexplicable when regarded as mere movements and changes of patches of colour, which are as incapable of hunger as a triangle is of playing football.

It is easy to see how assuming that physical objects really exist makes things simpler. Suppose the cat appears in one part of the room at one moment, and in another part later. We naturally suppose the cat has moved between those places, passing through a series of positions along the way. But if the cat is merely a set of sense-data, it cannot have been anywhere I did not see it. So we must suppose the cat did not exist at all while I was not looking. Instead, the cat suddenly came into existence in a new place. If the cat exists whether I see it or not, our own experience helps us understand its hunger between meals. But suppose the cat does not exist when I am not looking at it. Then it seems odd that its appetite should grow as fast during nonexistence as during existence. And if the cat consists only of sense-data, it cannot be hungry. Only my own hunger can be a sense-datum to me. So the sense-data that represent the cat to me behave quite naturally when understood as an expression of hunger. But their behavior becomes completely inexplicable if seen as nothing more than movements and changes in patches of color. Those patches are as incapable of hunger as a triangle is of playing football.

But the difficulty in the case of the cat is nothing compared to the difficulty in the case of human beings. When human beings speak—that is, when we hear certain noises which we associate with ideas, and simultaneously see certain motions of lips and expressions of face—it is very difficult to suppose that what we hear is not the expression of a thought, as we know it would be if we emitted the same sounds. Of course similar things happen in dreams, where we are mistaken as to the existence of other people. But dreams are more or less suggested by what we call waking life, and are capable of being more or less accounted for on scientific 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-data which have an existence not dependent upon our perceiving them.

But the difficulty with the cat is nothing compared to the difficulty with human beings. When people speak, we hear certain sounds that we associate with ideas. At the same time, we see certain lip movements and facial expressions. It is very difficult to suppose that the sounds we hear do not express a thought. We know those sounds would express a thought if we made them ourselves. Of course, similar things happen in dreams, when we mistakenly believe that other people exist. But dreams are shaped to some extent by what we call waking life. And dreams can be explained to some extent by scientific principles if we assume a physical world really exists. So every principle of simplicity urges us to accept the natural view. There really are objects beyond ourselves and our sense-data, and those objects exist independently of our perceiving them.

Of course it is not by argument that we originally come by our belief in an independent external world. We find this belief ready in ourselves as soon as we begin to reflect: it is what may be called an instinctive belief. We should never have been led to question this belief but for the fact that, at any rate in the case of sight, it seems as if the sense-datum itself were instinctively believed to be the independent object, whereas argument shows that the object cannot be identical with the sense-datum. This discovery, however—which is not at all paradoxical in the case of taste and smell and sound, and only slightly so in the case of touch—leaves undiminished our instinctive belief that there are objects corresponding to our sense-data. Since this belief does not lead to any difficulties, but on the contrary tends to simplify and systematize our account of our experiences, there seems no good reason for rejecting it. We may therefore admit—though with a slight doubt derived from dreams—that the external world does really exist, and is not wholly dependent for its existence upon our continuing to perceive it.

Of course, we do not first come to believe in an independent external world through argument. We already hold this belief when we begin to reflect. We may call it an instinctive belief. We would never have questioned this belief except for one problem. At least with sight, we seem instinctively to believe that the sense-datum itself is the independent object. Yet argument shows that the object cannot be identical with the sense-datum. This discovery is not at all surprising with taste, smell, and sound, and only slightly surprising with touch. But the discovery leaves our instinctive belief that there are objects corresponding to our sense-data just as strong. This belief creates no difficulties. On the contrary, it helps us explain our experiences more simply and systematically. So there seems to be no good reason to reject the belief. We may therefore accept that the external world really exists, though dreams give us some slight doubt. Its existence does not depend entirely on our continuing to perceive it.

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

The argument that led us to this conclusion is certainly weaker than we would like. But it is typical of many philosophical arguments, so we should briefly consider its general nature and validity. We find that all knowledge must be built on our instinctive beliefs. If we reject these beliefs, nothing is left. But some of our instinctive beliefs are much stronger than others. Through habit and association, many have become tangled up with other beliefs that are not truly instinctive. We mistakenly treat these other beliefs as part of what we believe instinctively.

Philosophy should show us the hierarchy of our instinctive beliefs, beginning with those we hold most strongly, and presenting each as much isolated and as free from irrelevant additions as possible. It should take care to show that, in the form in which they are finally set forth, our instinctive beliefs do not clash, but form a harmonious system. There can never be any reason for rejecting one instinctive belief except that it clashes with others; thus, if they are found to harmonize, the whole system becomes worthy of acceptance.

Philosophy should rank our instinctive beliefs, starting with those we hold most strongly. It should present each belief as separately as possible, with as few irrelevant additions as possible. Philosophy should show that, in their final form, our instinctive beliefs do not conflict but fit together into a consistent system. The only possible reason for rejecting an instinctive belief is that it conflicts with other instinctive beliefs. So, if these beliefs prove consistent with one another, the whole system deserves acceptance.

It is of course possible that all or any of our beliefs may be mistaken, and therefore all ought to be held with at least some slight element of doubt. But we cannot have reason to reject a belief except on the ground of some other belief. Hence, by organizing our instinctive beliefs and their consequences, by considering which among them 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, though the possibility of error remains, its likelihood is diminished by the interrelation of the parts and by the critical scrutiny which has preceded acquiescence.

Of course, it is possible that all or any of our beliefs may be mistaken. So we should hold all our beliefs with at least a little doubt. But we can have reason to reject a belief only on the basis of some other belief. We can therefore organize our instinctive beliefs and their consequences. We can consider which beliefs we could most readily change or abandon, if necessary. By doing so, we can build an orderly system of knowledge, using only our instinctive beliefs as our starting points. Although the possibility of error remains, the connections between the parts of this system make error less likely. So does the critical examination we carry out before accepting the system.

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

At least philosophy can serve this purpose. Most philosophers, rightly or wrongly, believe philosophy can do much more. They believe it can give us knowledge about the universe as a whole and the nature of ultimate reality. They believe this knowledge cannot be gained in any other way. Whether or not they are right, philosophy can certainly serve the more modest purpose we have discussed. For those who have begun to doubt whether common sense is enough, this purpose certainly justifies philosophy’s difficult, demanding work.