According to realism, I have argued, we never know “ideas” but always independent things, or rather states of affairs. It seems to me to follow that such expressions as appearances or data, and as concepts, percepts or sensa have no place in realist theory. If, e.g., there is a peculiar way of knowing called “sensing”, it will only be on the assumption that relations somehow constitute their terms that we can use the term “sensa” to describe a class of things or a way of being. If, on the other hand, any class of things can properly be described as “sensa”, to speak of knowing them as “sensing” is to make the same sort of assumption, and is no more justifiable than to speak of knowing trees as “treeing”. I should maintain that there is no such thing as either sensing

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or sensa, since “the sensa which I sense” are taken to be those things, my knowing which depends on where and how I am, and since this (a) does not describe the things, (b) is true of all my knowing.

For Berkeley the things we know are “essentially related to our minds” and thus have a “relative existence”, as our ideas. The theory of sensa is likewise a theory of “relative existence”, in someone's or some “sense-field”, and of “that whose nature it is to have certain relations”. Dr Broad's theory, in this connection, does not, I think, differ greatly from other theories of sensa. Sensa are shown to be private and non-physical because of their dependence on certain conditions. Dr Broad does not commit himself to the view that sensa are mind-dependent. “The facts are on the whole much better explained by supposing that the sensa which a man senses are partly dependent on the position, internal states and structure of his body”. But certain examples, though they “do not suggest for a moment that sensa are existentially mind-dependent…do strongly suggest that they are to some extent qualitatively mind-dependent”.note Now dependence is presumably a relation, and if a certain existence or a certain quality depends on something, this does not justify us, rejecting as we do the theory of constitutive relations, in describing it as a “dependent existence” or a “dependent quality”. The existence or quality, though it might not have been but for that other thing, is independent in the sense of being distinct and having a character of its own. If Dr Broad's explanations were correct, we should have to say that a certain thing now exists because my body was in a certain position, etc., and has certain qualities because my mind was in a certain condition. Granted all that, the thing now exists and has these qualities, and no reason has been shown for calling it private or non-physical.

Whether the explanations should be accepted is made exceedingly doubtful by noting the ambiguity of the statement that “the sensa which a man senses” are dependent on his body. This may merely mean that what is dependent is “the fact that he senses these sensa”, i.e., his sensing them, i.e., his standing in a certain relation to them. That this should be dependent on where he is could occasion no surprise to commonsense, and would justify no statement about the dependence of the “sensa” themselves. The fundamental criticism is, however, that what exists because of me nonetheless exists, apart from or independently of me. The houses which would not have existed, had not men planned and built them (i.e., but for their minds and bodies), are physical and are not private to these men; they stand for other men to see them and may remain when no one perceives them at all. The argument from dependence commits us to the Berkeleian theory of “relative existence”; as does also the notion of a special “sense-field” in which a given sensum occurs. Dr Broad regards it as a merit of his sensum theory that it does not require the assumption of an absolute Space-Time. But “absolute” Space-Time is simply that in which things “absolutely” exist, and realism

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is committed to the rejection of “relative existence”, and so of “relativity”.

It may now be asked what reasons there are for supposing “sensible objects”, which differ from physical objects, and which are brought about and affected by persons to a greater degree than the latter. In arguing that there can be no adequate reason for such a supposition, I shall consider mainly the question of “sensible” shapes and sizes. Dr Broad explains “the notion of sensible appearance”, in regard, particularly, to shape, as follows: “We know that when we lay a penny down on a table and view it from different positions, it generally looks more or less elliptical in shape. The eccentricity of these various appearances varies as we move about, and so does the direction of their major axes.…It is a fact that we do believe [that there is a single physical object…which appears to us in all these different ways]. It is an equally certain fact that the penny does look different as we move about.”note There then arises a difficulty about the relation between the round penny and an “elliptical appearance”, or something “appearing elliptical”. As regards the latter alternative (which Dr Broad rejects and which he connects with the theories of Professor Dawes Hicks and Professor Moore), it seems to me necessary to point out that “appearing” is a relation, viz., that of being known or apprehended. So that what is apprehended in this case is that “something is elliptical”, and, since this interpretation does not allow us to speak of “an appearance”, the precise belief would seem to be that the penny is elliptical; a belief which is simply false. Now there are cases in which such a false belief is held, but in many cases it is not, so that it may be questioned whether anything “appears elliptical”. In any case, “appearing elliptical” does not state a relation between the penny and us, except when we are wrong.

“Appearing elliptical” at least involves apprehension of a state of affairs, but, according to Dr Broad, the “elliptical appearance” is apprehended without judgment, though it is apprehended as existing. This compromise is as unacceptable as that of Berkeley. We have something whose “whole nature” is apprehended (since an appearance is exactly what appears to a person), and then it is supposed to exist. As before, its nature and its existence must mean the same thing, and it must be perfectly indescribable. A similar point emerges in connection with the “different appearances” mentioned. Unless we think of a physical object as something which has to be known in its “whole nature”, there is no reason why it should not have different appearances, i.e., why different characteristics of it should not be observable from different standpoints.note And it cannot be denied that when we do know a physical object, we know a variety of distinct things about it. The recognition that, whenever we know, we know existences and that to know existences is to know

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states of affairs in which complex things occur, is sufficient to dispose of the theory of “appearances”.

Thus an “elliptical appearance”, in respect of the penny, can only mean a false belief. I have said that in many cases this false belief is not held; what visibly appears to us is the round penny (or the penny's being round), even though the round surface is not at right angles to the line of vision. The assumption underlying the whole theory of differing shapes and sizes, seen from different directions and distances, is that we look out at, or there visually appears to us, a plane projection of the visual field. It is quite certain that a penny may be so placed that its projection on a plane perpendicular to the line of vision is elliptical; it is equally certain that the further a penny is beyond such a plane, the smaller its projection on the plane will be, and that it may be so near the plane that its projection is larger than that of the moon. But if, as is the case, it is not true that, when we look out, we either look at or see things arranged in a plane, if we do see things at various distances and at various angles to one another — in short, in three dimensions — then the contention that a thing looks smaller as it retreats, or that a round disc looks elliptical when it is oblique, is robbed of its force. Since we see things in three dimensions, there is no reason why we should attribute to a thing itself the shape of its projection on a plane perpendicular to the line of vision, or see that shape at all.

In cases where there is said to be an “elliptical appearance”, there really is something elliptical, viz. (assuming the surface affected to be plane and perpendicular, or sufficiently near the perpendicular, to the line of vision), that part of the surface of the retina on which the rays of light from the object fall. As we are not looking at the retina, this does not affect the question directly. But it is sometimes assumed (on a theory similar to Berkeley's) that the retina is affected in precisely the same way, no matter how far the light has travelled; that consequently we cannot distinguish distances by sight, so that any part of a visual object, or field, must “visually appear” to be at the same distance as any other part. (What distance this could be is quite obscure.) It is, however, perfectly conceivable that rays from different distances should affect the retina differently; even though “the picture imprinted on the retina” remained the same, the effects might differ in other respects. The fact is that we do see things at different distances, and if it is alleged that this must be due to something not given by vision, the answer is (a) that what it is due to is quite irrelevant, (b) that the objection involves the attempt to maintain that we cannot see what we actually do see.

But, though reference to the retina is irrelevant, there may still be something elliptical to be considered. We commonly see things against a background, and if that background were perpendicular to the line of vision, the shape of the part of the background concealed by the thing would be that of the thing's projection on a perpendicular plane. In this way an oblique penny may conceal an elliptical part of the wall of a room — and this also happens in cases where we are looking obliquely at

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the wall. Now we are just as capable of observing that an elliptical part of the wall is concealed as of observing the round penny; and the concealed elliptical part is just as much a physical object as the penny. In such a case, on a casual glance, we may fail to distinguish the distances of wall and penny, and suppose that the penny is elliptical. There is something elliptical in the same direction as the penny, something moreover of which we only see the shape, and there is a consequent possibility of our attributing that shape to the seen penny. If, however, something in the appearance of the object suggests that it is a penny, then we doubt the supposition we have made, and by stricter attention observe that the penny is not in the plane of the wall but is oblique and round. The previous mistake may be described by saying that we had “displaced” the elliptical shape from the wall to the penny, just as we might displace the red colour of red spectacles to the things we saw through them. Also, the fact that we know that the penny is round need not prevent us from making the mistake; it would only require to be two different processes which had the two beliefs, and we should attribute “knowledge” to that process which was able to overcome the other when they came into conflict.

It is possible for us, then, correctly to distinguish something elliptical from something round, the two being physical objects occupying different places; whereas, if we could only distinguish things in accordance with their projections, almost all our observations would be mistaken. It may be said that we can judge or discriminate best the shapes of surfaces which are perpendicular to the line of vision.note But though we could less easily distinguish a circle and a nearly circular ellipse if they were lying obliquely to our vision, that would not prove that we see their projections. We may tend to err by assuming that the easier conditions are fulfilled, but it is possible, when we are presented with an oblique circle, to “see it circular”. Again, we can judge sizes best when the things compared are close together; but we can see a distant tree larger than a man near at hand, who, if he stepped aside, would conceal the tree, and the relative sizes of the projections only appear to us in terms of concealed portions of a common background. Improvement in discrimination is possible, and may come about with the aid of other senses, as well as through the movements of the observed things and of ourselves in observing them. But it could never begin if we saw a flat picture.

I have considered at length the case of “elliptical appearance” in order to show the kind of mistake that is possible (though not necessary), and the possibility of correcting it by means of other judgments. I regard the general theory that I have advanced, as showing that an account along similar lines could be given of more difficult cases. In general, it cannot be maintained that in this (or any other) sort of apprehension, judgment, i.e., apprehension of states of affairs or situations, is not

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involved, since (a) it is always something that appears elliptical or smaller; we do not apprehend “ellipticity” or “smallness” by itself; (b) that something is always taken to be in some particular place. Any such judgment will be either correct or mistaken; but correction will only occur by means of judgments of the same order. At no time in the process of making our observations more precise, i.e., of discovering new distinctions and connections, as well as previous errors (and it is just in these ways that, on any view, we extend our knowledge of physical objects), do we suppose that we are not observing the things themselves and their actual shapes and sizes: at no time do we distinguish a “datum” or “sensum” from a thing. There is no thing or quality, then, which we can suppose ourselves to know “all about”; discrimination and association are always possible — whereas a “datum” could enter into no proposition. The same considerations are applicable to all the so-called sensa. The artist comes to discriminate and know colours better; and we can apprehend by sight many other qualities besides colour. What we see, like what we apprehend in any other way, is always complex, always a state of affairs; and the physical object is no more to be supposed to lack the “secondary qualities” than to lack the shapes which we see.