Discussion: Berkeley's New Theory of Vision Author(s): David M. Armstrong Source: Journal of the History of Ideas, Vol. 17, No. 1 (Jan., 1956), pp. 127-129 Published by: University of Pennsylvania Press Stable URL: http://www.jstor.org/stable/2707690 Accessed: 10/12/2008 06:34 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http://www.jstor.org/action/showPublisher?publisherCode=upenn. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit organization founded in 1995 to build trusted digital archives for scholarship. We work with the scholarly community to preserve their work and the materials they rely upon, and to build a common research platform that promotes the discovery and use of these resources. For more information about JSTOR, please contact
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DISCUSSION: BERKELEY'S NEW THEORY OF VISION BY DAVID M. ARMSTRONG
I should like to comment on three points in Mr. C. M. Turbayne's article " Berkeley and Molyneux on Retinal Images." 1 1. Mr. Turbayne argues that the identification of 'the proper objects of sight' with retinal images, which Berkeley seems to make at the beginning of his discussion of the inverted retinal image in his New Theory of Vision, is only a concession to current theory. But Mr. Turbayne also points out that the essay contains no explicit denial of this identification. Berkeley is more definite in The Theory of Vision Vindicated (paragraphs 50-51) yet there he says that retinal images are really only tangible objects, and fails to discuss the little pictures, visible (under suitable circumstances) to an observer who looks into somebody's eye. Now the problem here, surely, is why Berkeley makes such heavy weather with this 'knot,' as he calls it. For, it seems, he might have dealt with the problem in the same way that he dealt with the view that distance is judged by geometrical methods. He had argued that the lines and angles by which we are supposed to judge distance by the eye are not themselves visible, and in the same way he might have pointed out that, in seeing, the retina is never seen. Supposing, for the sake of argument, a visual picture did accompany our seeings, and it was inverted with respect to the objects seen, there would be no reason to identify it with the 'proper objects of sight,' it would simply be an accompaniment or condition of vision. Instead, he tries to overcome the difficulty by bringing in his view that the immediate objects of sight are not identical with the immediate objects of touch, and then arguing that, once this is granted, the little pictures are not really inverted at all relative to the perceiver. But, of course, in order to use the straightforward argument mentioned above Berkeley would have to distinguish clearly the observer's proper objects of sight from the little pictures another can see in the observer's eye. Now it seems to me that there is a very good reason why he never makes this distinction. It lies in the nature of the argument he uses to prove that distance is never immediately seen. In paragraph 2 he says: . . .distance of itself and immediately, cannot be seen. For distance being a line directed end-wise to the eye, it projects only one point in the fund of the eye, which point remains invariably the same, whether the distance be shorter or longer. But this argument is only valid on the assumption that it is the retina (the fund) which is the immediate object of sight. This commits Berkeley to the identification of retinal image and immediate object of sight. And so when he comes to discuss the 'knot' of the inverted image he is hoist with his own petard. Against Mr. Turbayne, therefore, I should argue that his failure to distinguish the two is not simply dialectical. To make the distinction would involve exposing the weakness of one of his own arguments. 2. But even if the immediate objects of sight have to be identified with the retinal image this does not necessarily destroy Berkeley's contention that 1 This
journal, XVI (June, 1955), 339-355. 127
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DAVID M. ARMSTRONG
the visible retina is an object quite distinct from, although connected with, the tangible retina, and Mr. Turbayne discusses the question what sort of things Berkeley took to be the 'proper objects of sight.' He says, quite correctly, that Berkeley denied that what we immediately see is flat, but he fails to point out that to attribute a 'flat-image' view to Berkeley, although strictly incorrect, is nevertheless quite near the truth. The trouble about flatness is that it presupposes the existence of three dimensions, for it is only surfaces which can be said to be flat or not flat, and surfaces must be surfaces of volumes, and volumes are three-dimensional. Now Berkeley denies that 'visible extension' is three-dimensional, and so he must deny that it is flat. But it is clear, I think, that he held that the immediate object of sight was a two-dimensional manifold, and a merely two-dimensional manifold is different from, but has very close resemblances to, a flat surface. It is true that Berkeley never explicitly says that the immediate objects of sight are two-dimensionally ordered, but this view seems inevitable if we consider how objects in the visual field would be described on the assumption that distance was not immediately perceived by sight. The objects would not have relations of near and far, but they would be to the right and left, above and below, each other, i.e., they would form a twodimensional field. Against this interpretation two arguments may be adduced from the text. In the first place, it may be pointed out, Berkeley seems to deny, at times, that such terms as ' high ' or ' low' can be applied to the immediate objects of sight.2 But all he means is that such words as 'right,' ' left,' 'above,'' below,' get their primary application from tactual experience; he does not deny that there are corresponding relations in the objects immediately seen.3 In the second place, it may be objected, he often says that all that is immediately seen is "light and colours," there is no mention of any two-dimensional order which they have. However, at other times, he gives a fuller account of the matter. In The Theory of Vision Vindicated (paragraph 44) he says: The proper, immediate object of vision is light, in all its modes and variations, various colours in kind, in degree, in quantity; some lively, others faint; more of some and less of others; various in their bounds or limits; various in their order and situation (-my italics). Elsewhere he speaks of "the magnitude or extension of the visible object" as being immediately perceived by sight.4 All this would be unintelligible if the visual field did not have dimensions; it is not three-dimensional according to Berkeley, so he must be thinking of it as two-dimensional. Berkeley's denial that we see a flat field has led to confusion because it has not been seen (as Berkeley did see) that a two-dimensional manifold cannot meaningfully be said to be flat. 3. Finally, I should like to make some comments on the oft-repeated view, endorsed by Mr. Turbayne, that the New Theory of Vision is a sort of half-way house to Immaterialism, because it tries to show that visible objects, at least, are not outside the mind. This view was taken by Berkeley himself, and in the Principles (paragr. 43) he writes: 2
Cf. New Theory of Vision, paragr. 95. paragr. 46.
3
Cf. The Theory of Vision Vindicated, 4 New Theory of Vision, paragr. 56.
BERKELEY'S
NEW
THEORY OF VISION
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For that we should in truth see external space and bodies actually existing in it, some nearer, others farther off, seems to carry with it some opposition to what hath been said of their existing nowhere without the mind. The consideration of this difficulty it was that gave birth to my Essay towards a New Theory of Vision, which was published not long since. And at several points during the Essay Berkeley implies that, having shown that the immediate objects of sight are not at a distance from us, he has thereby shown they are 'in the mind.' But, against Berkeley, it can be easily shown that the doctrines of the Essay are completely independent of the contentions of the Principles. In the first place, even if visual space is three-dimensional, this is in no necessary conflict with Immaterialism. He admits this in the Three Dialogues: Philonous. But allowing that distance was truly and immediately perceived by the mind, yet it would not thence follow it existed out of the mind. For whatever is immediately perceived is an idea: and can any idea exist out of the mind? 5 In the second place, if visual space is two-dimensional this does not imply that the esse of visible objects is percipi. A two-dimensional manifold might exist independently of its perceivers as much as a three-dimensional one. In showing, if he has shown it, that the visual field is two-dimensional only, Berkeley has shown that it makes no sense to ask how far away from us any object in the field is. But he seems to pass from this to thinking of the visual field as being at no distance from me in the sense in which my brains are at no distance from the inside of my skull, because that is where they are. He concludes from this, by a further illegitimate step, that because the visual field is in me, it is in my mind, in the sense in which 'in my mind' is a way of saying its being lies in being perceived. This 'argument' requires only to be stated to be refuted. In the Essay Berkeley speaks in a materialist way about the immediate objects of touch-they are physical objects in circumambient space. But, of course, his doctrine of the immediate objects of touch can be quite easily fitted into an Immaterialist framework also. Tangible objects in circumambient space do not exist independently of their being perceived, but, depending on which of the Berkeleyan analyses of statements about unobserved objects we adopt, we can say either that they are perceived by God, or, that if we moved in certain directions (defined by reference to tactual experience), we would feel certain sorts of things. The points Berkeley was anxious to insist on would remain; the immediate objects of touch would be ordered in a three-dimensional way, and the notion of distance could be understood only in terms of tactual experience. The main doctrines of the Essay, the view that distance is never immediately seen, and the heterogeneity of the objects of sight and touch which this view implies, are, therefore, logically indifferent with respect to Immaterialism. They have their own interest, which is only obscured by this mistake. London University. 5
Three Dialogues Between Hylas and Philonous, First Dialogue, in The Works of George Berkeley, ed. Luce and Jessop (1949), II, 202.