A gross ambiguity exists in the literature regarding the meaning of the concept of visual space and physical space. The source of this ambiguity is discussed and analyzed. Two different concepts of consciousness are suggested in place of the former visual-physical space dichotomy.
There is a gross ambiguity in the meaning of the concepts of visual-space and physical-space in the literature. Sometimes these concepts refer either directly or by implication to the Berkelian concept of cognition; sometimes they refer directly or by implication to the Kantian concept of cognition; and sometimes more than one interpretation appears in the same paper. The result is confusion in a clear understanding of visual perception.
This paper will (1) identify the meaning of these interpretations; (2) discuss their chief contradictions; and (3) suggest a new terminology to assist in clarifying some of the problems involved.
The Berkelian meaning of visual space is exemplified in a quotation by Ogle1. Ogle quotes Hering as translated by Hoffman:
"It is a familiar fact that we do not always see objects in our environment exactly in the shape and spatial arrangement that is 'actually' theirs, according to the totality of our experience. Especially striking differences arise from the fact that all objects observed from a great distance appear much smaller than when observed close to. The apparent size relations of the separate parts of objects which have a considerable depth extension do not coincide with the actual ones…Accordingly we must differentiate between the real objects and the visual perceptions that are elicited by 'subjective visual objects.' The totality of all the simultaneous visible subjective visual objects forms the subjective visual space, or the subjective visual field. In objective space these correspond to the objective visual field, that is, that portion of actual space that is visible to us at one time in one given eye position.
"But the difference between the spatial characteristics of the external object and its corresponding subjective visual object, between objective visual space and subjective visual space, is even more extensive than the above examples show, since they only illustrate the manifold contradictions between the two. When we apply a measuring rod to an object, and measure its extent, we do indeed obtain its objective extent, but we do not ascertain any information as to the subjective size of the measuring rod or the object we have measured with it. Under certain conditions the two objects may appear to be of different size. Look with one eye, while the other is closed, at a window several meters away. Then hold one finger so close in front of the active eye that you have to accommodate on it with difficulty. As soon as this is done, the window shrinks and seems smaller than when one observes it without the effort of accommodation. Of course, a measuring rod behaves in precisely the same way if it is applied to the window at that time. Thus, the objective size of the window gives us no information as to the subjective size, either of the measuring rod or of the object—the window—that it measures. The spatial extent of objects does not give us any standard for the size of subjective, visual objects.
"…We can only demonstrate changes in the standard of the subjective visual field. In ourselves we can determine those changes subjectively by comparison with former experiences, such as in the above experiment with the window. In the case of other individuals, we usually have to resort to such comparisons and the statements of the people concerned. In view of the above, it is impossible to compare the absolute size of subjective visual objects with the imagined real size of objects. We can only compare the size relationships of subjective visual objects and the mutual position of the corresponding external objects."
The use of the term "visual objects" by Hering derives from Berkeley's "Essay Towards a New Theory of Vision." Readers of Berkeley2 can observe that his essay is more than a treatise on vision. It is also an essay on metaphysics; on the nature of existence. Berkeley makes a radical point in his essay about the nature of reality. He claims that the entity which is perceived by sight is radically different than the entity perceived by touch. It is, he claims, numerically different, and specifically different. It is not the same. Berkeley bases his whole theory on the causal theory of perception. This theory of cognition holds that reality is the cause of perception, but not the object of perception. Berkeley expands his whole theory on these premises and the contradiction which invalidates his theory is this: perception is not, nor cannot be, an object of cognition. It is a form of cognition, and because of this one cannot speak of perceiving a perceptiona. One can only speak of awareness of a unitary reality, to a greater or lesser degree. For example, the causal theory allowed Berkeley, and others, to conceive of a consciousness perceiving retinal images, because he held that what is perceived was not reality but rather "visual objects." These visual objects, according to Berkeley, are a type of flat visual field of color and form that exists "somewhere" in the mind. Berkeley develops the dichotomy of the visible object (the visual object) and the tangible object as being two separate, and distinct, spatially unrelated entities. Thus the space we see and the space we touch (or measure) are not the same spaces.
Berkeley's theory should be rejected because it flatly contradicts the law of identity and all rational argument presupposes this law. A thing cannot be itself and something else simultaneously.
Consider the following examples of the Berkelian frame of reference. (These examples are random selections, which are used to illustrate the point of this paper. They are not evaluations of the papers or books themselves.)
Gibson3a says, "A visual object in depth may be analyzed in terms of several abstract variables which are interrelated to one another."
Or, consider the following quotation by Alberta Gilinsky4: "The perception of distance or depth is a fact, and must be included in a generalized theory. But that does not mean the true or physical distance D, for the physical distance is not perceived. What is sensed or perceived is the perceived distance d, and that is the only distance that is subjectively realized and therefore…."
The question to ask Gilinsky is: "What other distance exists that we may perceive, apart from the 'real' distance?" The answer must be, of course, none. Gilinsky's error is in holding the premise of the causal theory, and assuming that one can perceive a perception. One cannot, and because of this, the concept of perceived distance, as used in Gilinsky's context, takes on a very obscure meaning that renders precise identification, by valid definition, difficult indeed— if not impossible.
A second and equally erroneous interpretation of visual space is the Kantian interpretation. It is also based on the causal theory. Space was unitary to Kant, but it, along with 13 other automatic functions such as causality and time, were imposed automatically and innately by an "a priori intuition." A priori intuition has been compared to a little man in the mind who sticks qualities into the raw sense data, beneath the level of consciousness. We, as observers, experience things always after something has been "automatically" added by mind. We thus never encounter reality as it is, said Kant, but only as it "appears" to be. This appearance he labeled the phenomenal world, and the real world he called the noumenal world. True reality, said Kant, exists but is unknowable. Kant's contradiction is basic. If reality is unknowable, how does Kant know it exists? Kant uses the concept of "knowledge," which means "knowledge of something that exists (or did exist)," and simultaneously denies that one can have knowledge of existence! This contradiction, plus the causal theory contradiction, invalidate the Kantian interpretation of the visual perception of space.
Now consider the Kantian premises of Gilinsky in the following: "The real objective size of a physical object is subjectively unknowable." One question to ask Gilinsky (and the scientists who share her premises) is: "What other size exists other than the real one that we may perceive?" Gilinsky epistemologically regards perceived size in a similar manner as perceived distance. What is perceived in her view is perceived size, but, as we shall see, perceived size and perceived distance are actions of visual consciousness, or visual perception. As such they cannot be perceived. They are forms of awareness of reality, not objects of awareness. The only objects of awareness (in the context of this discussion) are metaphysical (the real) distance and size.
Another typical example of the Kantian interpretation of visual space is shown in a quotation by Gordon Walls:5
"Although the innateness of the concept of spatiality has been considered one of the givens ever since Kant, the ordering and the occupation of visual space is by the things we see in it. If those things are projected then necessarily so is the space. No, we have no visual impression that is detached from, or in any way different from, the visual percept—the thing as perceived, and where perceived, which we take to be the real object until we are taught betterb."
Or: Consider the following statement by Gibson3b: "To what extent can we now account for the perception of the phenomenal world which is adequate for behavior?"
Or: Consider the sentences of Luneburg6: "Visual sensations are established under the influence of many different factors. They are the result of an activation of the mind by physical light stimuli and are distinguished by a remarkable degree of certainty and definiteness which tempts us to believe that the external world itself is revealed to us, and not merely an image of our own makingb."
The Kantian interpretation of the visual perception of space should be rejected because all consciousness is consciousness of reality. If reality (existence) is removed, there is nothing left to be conscious of. "Consciousness is the faculty of awareness—the faculty of perceiving that which exists."7
It is not irrelevant to this discussion to point out that this scientific confusion is caused by a priori explicit or implicit philosophic confusion. In view of these ambiguities, the best definition of visual and physical space is probably that mentioned by Graham8:
"The definition of physical space has the set of points ordered by physical measurement, whereas visual space can be thought of as the set of points ordered by a subject's discrimination following certain classes of "space" instruction—such as "make an adjustment until the apparent distance between your setting and the light point to the left is the same as your setting and the light point to the right."
If we examine this definition we find it is possible to make a more basic identification of visual and physical space. The common denominator of visual and physical space, as given by Graham, is that both are actions of consciousness. The essence of visual-physical space experiments is that they endeavor to relate spatial relations as they are sensed or perceived visually with spatial relations as they are measured. The former is an act of consciousness limited to the visual perceptual level, as it identifies the spatial attributes of reality. On the other hand, physical space is seen to be an action of consciousness, at the conceptual level, as it identifies the spatial attributes of reality by measurement. Both these are concepts of consciousness. Now the concept of "space" is a metaphysical concept (i.e., a concept of existence). Space and/or spatiality is an attribute of existence defined by extension in three dimensions. The term, physical space, on analysis, means "space being conceived by measurement," and yet it more naturally is regarded as the metaphysical concept of space. Above and beyond this confusion are the implications of Berkeley and Kant that remain associated with the terms, visual and physical space.
The end result is a confused concept, which unnecessarily complicates a complex subject to being with. Can some of this confusion be clarified? I think it can be significantly clarified by abandoning the terms, physical and visual space, entirely and substituting in their place the following terms:
(a) In place of the concept, visual space, the term, "perceived space." This term, in full context, means: visual consciousness of space, or, visually perceived space, or space being perceived visually, or visual perception of space. At present the use of the term, perceived space, occurs ambiguously at times in the literature, where it is often used interchangeably with visual space9. All ambiguity is removed by eliminating the term, visual space, and using the term, perceived space, in the above context.
(b) In place of physical space, the term, "the conception of space by measurement," or, space being conceived by measurement.
The concepts of objective and subjective space are ambiguous and equivocal for essentially the same reasons as are the concepts of visual and physical space, and it is held therefore that their usage be discontinued also.
By dropping completely the of physical and visual space and substituting the actual descriptions of the actions of consciousness involved, the following advantages are achieved:
(a) It dispenses entirely with all implications of the contradictory causal theory of perception.
(b) It dispenses entirely with all implications of Berkeley's dualism.
(c) It dispenses entirely with all implications and contradictions of Kantian phenomenalism.
(d) It substitutes, instead, two simples descriptions of consciousness perceiving the spatial attributes of reality. Both terms clearly and unequivocally identify the nature of the action of consciousness involved. For example, the action of consciousness in the former is strictly limited to the visual perceptual level. The latter term clearly points out to us a crucial difference in the action of consciousness, which now involves the lower range of the conceptual level of consciousness, but which is still clearly differentiated from the other higher and more complex actions of consciousness at the conceptual level, such as abstraction and concept formationc.
Using these new descriptions, then, it becomes incorrect to speak of the "perception of visual space," but correct to speak of the "visual perception of space." The former phrase implies one is perceiving a perception and the latter implies one is visually perceiving the spatial attributes of reality. The concepts of space, size, distance, etc., are regarded as metaphysical concepts of attributes of existence. They are objects of awareness. Perceived space, perceived size, perceived distance, etc., are regarded as specific actions of visual perceptual consciousness, engaged in the action of being aware of the spatial attributes (size, distance, etc.) of reality.
Dr. Richard Perkins is an optometrist. He has been engaged in private practice in St. Thomas, Ontario, for seventeen years. He graduated from the Ontario College of Optometry of Toronto, (now located at University of Waterloo, Waterloo, Ontario) in 1951. He has served on the executive board of the Ontario Provincial Optometric Association in the past, and at one time, served as abstract editor for the Canadian Journal of Optometry, to which he has contributed clinical papers. The concepts of Visual-space and Physical-Space, are anatomic-physiologic-perceptual concepts, taught to students of physiologic optics, and the paper is written specifically for such a scientific audience. However, the readers of Reason may be interested in the paper, since it demonstrates the role and importance of epistemology in science. Philosophically, Dr. Perkins is not of the Objectivist school, but is rather, a Rational Anarchist.
I thank Robert Efron, M.D., Chief, Neurophysiology-Biophysics Research Unit, Veterans Administration Hospital, Boston, Massachusetts, for his valuable suggestions in the preparation of this manuscript.
I thank also the W.B. Saunders Company, Publishers, West Washington Square, Philadelphia, Pa., for their kind permission to quote from Kenneth Ogles' book, Researches in Binocular Vision, 1950.
I am grateful to Dr. Leonard Peikoff, Professor of Philosophy at Brooklyn Polytechnic Institute for pointing this out to me in lectures he has publicly given, which elaborated on Miss Ayn Rand's original philosophy, Objectivism.
The theory of concept formation referred to is that given in reference No. 7.
1 Ogle, Kenneth N., Researches in Binocular Vision, Philadelphia, W.B. Saunders Co., 1950, pp. 10- 77.
2 Armstrong, D.M., Berkeley's Theory of Vision: A Critical Examination of Bishop Berkeley's Essay Toward a New Theory of Vision, Melbourne University Press, 1960.
3 Gibson, James J., The Perception of the Visual World, Boston, Mass., Houghton Mifflin Co., 1950.
3a Page 99.
3b Page 164.
4 Gilinsky, Alberta S., Perceived size and distance in visual space, Psych. Rev., 58: 460 - 482, 1957.
5 Walls, Gordon L., The problem of visual direction, Am. J. Optom., and Arch. Am. Acad. Optom., 28 (2): 55-83; (3): 115-146; (4) 173-212, 1951. Reprinted as Monograph No. 117 of the American Academy of Optometry.
6 Luneburg, Rudolf K., The metric of binocular visual space, J. Opt. Soc., Am., 40 (10): 627-642, 1950.
7 Rand, Ayn, Introduction to Objectivist Epistemology, The Objectivist, Inc. 20 East 34th St., New York, N.Y., Chapt. 4, Page 31, Paragraph 7.
8 Graham, Clarence H., editor, Vision and Visual Perception, New York, John Wiley & Sons., Inc., 1965, pp. 538-539.
9 Fry, Glenn A., Visual Perception of Space, Am. J. Optom. and Arch. Am. Acad. Optom., 27 (11): 531-553, 1950.