Kant's Theory of Knowledge

by H. A. Prichard

The case of colour, however, is more difficult. From the closeness of its relation to the shape of bodies, it seems to be a real quality of bodies, and not something relative to a sensitive subject like the other secondary qualities. In fact, so intimate seems the relation of colour to the shape of bodies, that it would seem—as has, of course, often been argued—that if colour be relative to a sensitive subject, the primary qualities of bodies must also be relative to a sensitive subject, on the ground that shape is inseparable from colour.[22] Yet whether this be so or not, it must, in the end, be allowed that colour does presuppose a sensitive subject in virtue of its own nature, and quite apart from the difficulty—which is in itself insuperable—of determining the right colour of individual bodies. It must, therefore, be conceded that colour is not a quality of bodies. But if this be true, the use of the term 'look' or 'appear' in connexion with colour involves a difficulty which does not arise when it is used in connexion with the primary qualities. Bodies undoubtedly look or appear coloured. Now, as has already been suggested,[23] the term 'look' seems to presuppose some identity between what a thing is and what it looks, and at least the possibility of cases in which they are what they look—a possibility which, as we have seen, is realized in the case of the primary qualities. Yet, if colour is not a quality of bodies, then, with respect to colour, things look what they never are, or, in other words, are wholly different from what they look;[24] and since it seems impossible to hold that colour is really a property of bodies, this conclusion must, in spite of its difficulty, be admitted to be true.

There remain, however, to be noticed two respects in which assertions concerning what things look in respect of colour agree with corresponding assertions in respect of the primary qualities. They imply that what we perceive is a reality, in the sense already explained.[25] Thus the assertion that the grass looks green implies that it is a reality which looks green, or, in other words, that the object of perception is a reality, and not an 'appearance'. Again, such assertions imply that the reality about which the assertion is made is spatial. The term 'grass' implies extension, and only what is extended can be said to look coloured. If it be urged that what looks coloured need only look extended, it may be replied that the two considerations which lead us to think that things only look coloured presuppose that they are spatial. For the two questions, the consideration of which leads to this conclusion, are, 'What is the right or real colour of an individual thing?' and 'Has it really any colour at all, or does it only look coloured?' and neither question is significant unless the thing to which it refers is understood to be spatial.

We may now return to the main issue. Is it possible to maintain either (1) the position that only appearances are spatial and possess all the qualities which imply space, or (2) the position that things only appear spatial and only appear or look as if they possessed the qualities which imply space? It may be urged that these questions have already been implicitly answered in the negative. For the division of the qualities of things into primary and secondary is exhaustive, and, as has been shown, the distinction between 'appearance' and 'reality', when drawn with respect to the primary qualities and to colour—the only secondary quality with respect to which the term 'appears' can properly be used[26]—presupposes the reality of space. Consequently, since we do draw the distinction, we must accept the reality of that which is the condition of drawing it at all. But even though this be conceded—and the concession is inevitable—the problem cannot be regarded as solved until we have discovered what it is in the nature of space which makes both positions untenable. Moreover, the admission that in the case of colour there is no identity between what things look and what they are removes at a stroke much of the difficulty of one position, viz. that we only know what things look or appear, and not what they are. For the admission makes it impossible to maintain as a general principle that there must be some identity between what they look and what they are. Consequently, it seems possible that things should be wholly different from what they appear, and, if so, the issue cannot be decided on general grounds. What is in substance the same point may be expressed differently by saying that just as things only look coloured, so things may only look spatial. We are thus again[27] led to see that the issue really turns on the nature of space and of spatial characteristics in particular.

[26] Cf. pp. 86-7.

[27] Cf. p. 79.

In discussing the distinction between the real and the apparent shape of bodies, it was argued that while the nature of space makes it necessary to distinguish in general between what a body looks and what it is, yet the use of the term look receives justification from the existence of limiting cases in which what a thing looks and what it is are identical. The instances considered, however, related to qualities involving only two dimensions, e. g. convergence and bentness, and it will be found that the existence of these limiting cases is due solely to this restriction. If the assertion under consideration involves a term implying three dimensions, e. g. 'cubical' or 'cylindrical', there are no such limiting cases. Since our visual perception is necessarily subject to conditions of perspective, it follows that although we can and do see a cube, we can never see it as it is. It is, so to say, in the way in which a child draws the side of a house, i. e. with the effect of perspective eliminated; but it never can be seen in this way. No doubt, our unreflective knowledge of the nature of perspective enables us to allow for the effect of perspective, and to ascertain the real shape of a solid object from what it looks when seen from different points. In fact, the habit of allowing for the effect of perspective is so thoroughly ingrained in human beings that the child is not aware that he is making this allowance, but thinks that he draws the side of the house as he sees it. Nevertheless, it is true that we never see a cube as it is, and if we say that a thing looks cubical, we ought only to mean that it looks precisely what a thing looks which is a cube.

It is obvious, however, that two dimensions are only an abstraction from three, and that the spatial relations of bodies, considered fully, involve three dimensions; in other words, spatial characteristics are, properly speaking, three-dimensional. It follows that terms which fully state spatial characteristics can never express what things look, but only what they are. A body may be cylindrical, and we may see a cylindrical body; but such a body can never, strictly speaking, look cylindrical. The opposition, however, between what a thing is and what it looks implies that what it is is independent of a percipient, for it is precisely correlation to a percipient which is implied by 'looking' or 'appearing'. In fact, it is the view that what a thing really is it is, independently of a percipient, that forms the real starting-point of Kant's thought. It follows, then, that the spatial characteristics of things, and therefore space itself, must belong to what they are in themselves apart from a percipient, and not to what they look.[28] Consequently, it is so far from being true that we only know what things look and not what they are, that in the case of spatial relations we actually know what things are, even though they never look what they are.

This conclusion, however, seems to present a double difficulty. It is admitted that we perceive things as they look, and not as they are. How, then, is it possible for the belief that things are spatial to arise? For how can we advance from knowledge of what they look to knowledge of what they are but do not look? Again, given that the belief has arisen, may it not after all be illusion? No vindication seems possible. For how can it be possible to base the knowledge of what things are, independently of perception, upon the knowledge of what they look? Nevertheless, the answer is simple. In the case of the perception of what is spatial there is no transition in principle from knowledge of what things look to knowledge of what things are, though there is continually such a transition in respect of details. It is, of course, often necessary, and often difficult, to determine the precise position, shape, &c., of a thing, and if we are to come to a decision, we must appeal to what the thing looks or appears under various conditions. But, from the very beginning, our consciousness of what a thing appears in respect of spatial characteristics implies the consciousness of it as spatial and therefore also as, in particular, three-dimensional. If we suppose the latter consciousness absent, any assertion as to what a thing appears in respect of spatial characteristics loses significance. Thus, although there is a process by which we come to learn that railway lines are really parallel, there is no process by which we come to learn that they are really spatial. Similarly, although there is a process by which we become aware that a body is a cube, there is no process by which we become aware that it has a solid shape of some kind; the process is only concerned with the determination of the precise shape of the body. The second difficulty is, therefore, also removed. For if assertions concerning the apparent shape, &c. of things presuppose the consciousness that the things are spatial, to say that this consciousness may be illusory is to say that all statements concerning what things appear, in respect of spatial relations, are equally illusory. But, since it is wholly impossible to deny that we can and do state what things appear in this respect, the difficulty must fall to the ground.

There remains to be answered the question whether Kant's position is tenable in its other form, viz. that while we cannot say that reality is spatial, we can and must say that the appearances which it produces are spatial. This question, in view of the foregoing, can be answered as soon as it is stated. We must allow that reality is spatial, since, as has been pointed out, assertions concerning the apparent shape of things presuppose that they are spatial. We must equally allow that an appearance cannot be spatial. For on the one hand, as has just been shown, space and spatial relations can only qualify something the existence of which is not relative to perception, since it is impossible to perceive what is spatial as it is; and on the other hand an appearance, as being ex hypothesi an appearance to some one, i. e. to a percipient, must be relative to perception.

We may say, then, generally, that analysis of the distinction between appearance and reality, as it is actually drawn in our ordinary consciousness, shows the falsity of both forms of the philosophical agnosticism which appeals to the distinction. We know things; not appearances. We know what things are; and not merely what they appear but are not. We may also say that Kant cannot possibly be successful in meeting, at least in respect of space, what he calls 'the easily foreseen but worthless objection that the ideality of space and of time would turn the whole sensible world into pure illusion'.[29] For space, according to him, is not a property of things in themselves; it cannot, as has been shown, be a property of appearances; to say that it is a property of things as they appear to us is self-contradictory; and there is nothing else of which it can be said to be a property.