Chapter IV. Idealism

by Bertrand Russell

　　The word 'idealism' is used by different philosophers in somewhatdifferent senses. We shall understand by it the doctrine that whateverexists, or at any rate whatever can be known to exist, must be in somesense mental. This doctrine, which is very widely held among philosophers,has several forms, and is advocated on several different grounds. Thedoctrine is so widely held, and so interesting in itself, that even thebriefest survey of philosophy must give some account of it.

　　Those who are unaccustomed to philosophical speculation may be inclined todismiss such a doctrine as obviously absurd. There is no doubt that commonsense regards tables and chairs and the sun and moon and material objectsgenerally as something radically different from minds and the contents ofminds, and as having an existence which might continue if minds ceased. Wethink of matter as having existed long before there were any minds, and itis hard to think of it as a mere product of mental activity. But whethertrue or false, idealism is not to be dismissed as obviously absurd.

　　We have seen that, even if physical objects do have an independentexistence, they must differ very widely from sense-data, and can only havea correspondence with sense-data, in the same sort of way in whicha catalogue has a correspondence with the things catalogued. Hence commonsense leaves us completely in the dark as to the true intrinsic nature ofphysical objects, and if there were good reason to regard them as mental,we could not legitimately reject this opinion merely because it strikes usas strange. The truth about physical objects must be strange. Itmay be unattainable, but if any philosopher believes that he has attainedit, the fact that what he offers as the truth is strange ought not to bemade a ground of objection to his opinion.

　　The grounds on which idealism is advocated are generally grounds derivedfrom the theory of knowledge, that is to say, from a discussion of theconditions which things must satisfy in order that we may be able to knowthem. The first serious attempt to establish idealism on such grounds wasthat of Bishop Berkeley. He proved first, by arguments which were largelyvalid, that our sense-data cannot be supposed to have an existenceindependent of us, but must be, in part at least, 'in' the mind, in thesense that their existence would not continue if there were no seeing orhearing or touching or smelling or tasting. So far, his contention wasalmost certainly valid, even if some of his arguments were not so. But hewent on to argue that sense-data were the only things of whose existenceour perceptions could assure us; and that to be known is to be 'in' amind, and therefore to be mental. Hence he concluded that nothing can everbe known except what is in some mind, and that whatever is known withoutbeing in my mind must be in some other mind.

　　In order to understand his argument, it is necessary to understand his useof the word 'idea'. He gives the name 'idea' to anything which is immediatelyknown, as, for example, sense-data are known. Thus a particular colourwhich we see is an idea; so is a voice which we hear, and so on. But theterm is not wholly confined to sense-data. There will also be thingsremembered or imagined, for with such things also we have immediateacquaintance at the moment of remembering or imagining. All such immediatedata he calls 'ideas'.

　　He then proceeds to consider common objects, such as a tree, for instance.He shows that all we know immediately when we 'perceive' the tree consistsof ideas in his sense of the word, and he argues that there is not theslightest ground for supposing that there is anything real about the treeexcept what is perceived. Its being, he says, consists in being perceived:in the Latin of the schoolmen its 'esse' is 'percipi'. Hefully admits that the tree must continue to exist even when we shut oureyes or when no human being is near it. But this continued existence, hesays, is due to the fact that God continues to perceive it; the 'real'tree, which corresponds to what we called the physical object, consists ofideas in the mind of God, ideas more or less like those we have when wesee the tree, but differing in the fact that they are permanent in God'smind so long as the tree continues to exist. All our perceptions,according to him, consist in a partial participation in God's perceptions,and it is because of this participation that different people see more orless the same tree. Thus apart from minds and their ideas there is nothingin the world, nor is it possible that anything else should ever be known,since whatever is known is necessarily an idea.

　　There are in this argument a good many fallacies which have been importantin the history of philosophy, and which it will be as well to bring tolight. In the first place, there is a confusion engendered by the use ofthe word 'idea'. We think of an idea as essentially something insomebody's mind, and thus when we are told that a tree consists entirelyof ideas, it is natural to suppose that, if so, the tree must be entirelyin minds. But the notion of being 'in' the mind is ambiguous. We speak ofbearing a person in mind, not meaning that the person is in our minds, butthat a thought of him is in our minds. When a man says that some businesshe had to arrange went clean out of his mind, he does not mean to implythat the business itself was ever in his mind, but only that a thought ofthe business was formerly in his mind, but afterwards ceased to be in hismind. And so when Berkeley says that the tree must be in our minds if wecan know it, all that he really has a right to say is that a thought ofthe tree must be in our minds. To argue that the tree itself must be inour minds is like arguing that a person whom we bear in mind is himself inour minds. This confusion may seem too gross to have been really committedby any competent philosopher, but various attendant circumstances renderedit possible. In order to see how it was possible, we must go more deeplyinto the question as to the nature of ideas.

　　Before taking up the general question of the nature of ideas, we mustdisentangle two entirely separate questions which arise concerningsense-data and physical objects. We saw that, for various reasons ofdetail, Berkeley was right in treating the sense-data which constitute ourperception of the tree as more or less subjective, in the sense that theydepend upon us as much as upon the tree, and would not exist if the treewere not being perceived. But this is an entirely different point from theone by which Berkeley seeks to prove that whatever can be immediatelyknown must be in a mind. For this purpose arguments of detail as to thedependence of sense-data upon us are useless. It is necessary to prove,generally, that by being known, things are shown to be mental. This iswhat Berkeley believes himself to have done. It is this question, and notour previous question as to the difference between sense-data and thephysical object, that must now concern us.

　　Taking the word 'idea' in Berkeley's sense, there are two quite distinctthings to be considered whenever an idea is before the mind. There is onthe one hand the thing of which we are aware—say the colour of mytable—and on the other hand the actual awareness itself, the mentalact of apprehending the thing. The mental act is undoubtedly mental, butis there any reason to suppose that the thing apprehended is in any sensemental? Our previous arguments concerning the colour did not prove it tobe mental; they only proved that its existence depends upon the relationof our sense organs to the physical object—in our case, the table.That is to say, they proved that a certain colour will exist, in a certainlight, if a normal eye is placed at a certain point relatively to thetable. They did not prove that the colour is in the mind of thepercipient.

　　Berkeley's view, that obviously the colour must be in the mind, seems todepend for its plausibility upon confusing the thing apprehended with theact of apprehension. Either of these might be called an 'idea'; probablyeither would have been called an idea by Berkeley. The act is undoubtedlyin the mind; hence, when we are thinking of the act, we readily assent tothe view that ideas must be in the mind. Then, forgetting that this wasonly true when ideas were taken as acts of apprehension, we transfer theproposition that 'ideas are in the mind' to ideas in the other sense, i.e.to the things apprehended by our acts of apprehension. Thus, by anunconscious equivocation, we arrive at the conclusion that whatever we canapprehend must be in our minds. This seems to be the true analysis ofBerkeley's argument, and the ultimate fallacy upon which it rests.

　　This question of the distinction between act and object in ourapprehending of things is vitally important, since our whole power ofacquiring knowledge is bound up with it. The faculty of being acquaintedwith things other than itself is the main characteristic of a mind.Acquaintance with objects essentially consists in a relation between themind and something other than the mind; it is this that constitutes themind's power of knowing things. If we say that the things known must be inthe mind, we are either unduly limiting the mind's power of knowing, or weare uttering a mere tautology. We are uttering a mere tautology if we meanby 'in the mind' the same as by 'before the mind', i.e. ifwe mean merely being apprehended by the mind. But if we mean this, weshall have to admit that what, in this sense, is in the mind, maynevertheless be not mental. Thus when we realize the nature of knowledge,Berkeley's argument is seen to be wrong in substance as well as in form,and his grounds for supposing that 'ideas'—i.e. the objectsapprehended—must be mental, are found to have no validity whatever.Hence his grounds in favour of idealism may be dismissed. It remains tosee whether there are any other grounds.

　　It is often said, as though it were a self-evident truism, that we cannotknow that anything exists which we do not know. It is inferred thatwhatever can in any way be relevant to our experience must be at leastcapable of being known by us; whence it follows that if matter wereessentially something with which we could not become acquainted, matterwould be something which we could not know to exist, and which could havefor us no importance whatever. It is generally also implied, for reasonswhich remain obscure, that what can have no importance for us cannot bereal, and that therefore matter, if it is not composed of minds or ofmental ideas, is impossible and a mere chimaera.

　　To go into this argument fully at our present stage would be impossible,since it raises points requiring a considerable preliminary discussion;but certain reasons for rejecting the argument may be noticed at once. Tobegin at the end: there is no reason why what cannot have any practicalimportance for us should not be real. It is true that, if theoreticalimportance is included, everything real is of some importance tous, since, as persons desirous of knowing the truth about the universe, wehave some interest in everything that the universe contains. But if thissort of interest is included, it is not the case that matter has noimportance for us, provided it exists even if we cannot know that itexists. We can, obviously, suspect that it may exist, and wonder whetherit does; hence it is connected with our desire for knowledge, and has theimportance of either satisfying or thwarting this desire.

　　Again, it is by no means a truism, and is in fact false, that we cannotknow that anything exists which we do not know. The word 'know' is hereused in two different senses. (1) In its first use it is applicable to thesort of knowledge which is opposed to error, the sense in which what weknow is true, the sense which applies to our beliefs andconvictions, i.e. to what are called judgements. In this sense ofthe word we know that something is the case. This sort of knowledgemay be described as knowledge of truths. (2) In the second use ofthe word 'know' above, the word applies to our knowledge of things,which we may call acquaintance. This is the sense in which we knowsense-data. (The distinction involved is roughly that between savoirand connaître in French, or between wissen and kennenin German.)

　　Thus the statement which seemed like a truism becomes, when re-stated, thefollowing: 'We can never truly judge that something with which we are notacquainted exists.' This is by no means a truism, but on the contrary apalpable falsehood. I have not the honour to be acquainted with theEmperor of China, but I truly judge that he exists. It may be said, ofcourse, that I judge this because of other people's acquaintance with him.This, however, would be an irrelevant retort, since, if the principle weretrue, I could not know that any one else is acquainted with him. Butfurther: there is no reason why I should not know of the existence ofsomething with which nobody is acquainted. This point is important, anddemands elucidation.

　　If I am acquainted with a thing which exists, my acquaintance gives me theknowledge that it exists. But it is not true that, conversely, whenever Ican know that a thing of a certain sort exists, I or some one else must beacquainted with the thing. What happens, in cases where I have truejudgement without acquaintance, is that the thing is known to me by description,and that, in virtue of some general principle, the existence of a thinganswering to this description can be inferred from the existence ofsomething with which I am acquainted. In order to understand this pointfully, it will be well first to deal with the difference between knowledgeby acquaintance and knowledge by description, and then to consider whatknowledge of general principles, if any, has the same kind of certainty asour knowledge of the existence of our own experiences. These subjects willbe dealt with in the following chapters.