Читать книгу The Art of Seeing - Aldous Leonard Huxley - Страница 7

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Before undertaking a detailed description of the techniques employed by Dr. Bates and his followers, I propose to devote a few pages to a discussion of the process of seeing. Such a discussion will serve, I hope, to throw some light on the underlying reasons for these techniques, some of which might otherwise appear inexplicable and arbitrary.

When we see, our minds become acquainted with events in the outside world through the instrumentality of the eyes and the nervous system. In the process of seeing, mind, eyes and nervous system are intimately associated to form a single whole. Anything which affects one element in this whole exercises an influence upon the other elements. In practice, we find that it is possible to act directly only upon the eyes and the mind. The nervous system which connects them cannot be influenced except indirectly.

The structure and mechanism of the eye have been studied in minute detail, and good descriptions of these things can be found in any text book of ophthalmology or physiological optics. I will not attempt to summarize them in this place; for my concern is not with anatomical structures and physiological mechanisms, but with the process of seeing—the process whereby these structures and mechanisms are used to provide our mind with visual knowledge of the external world.

In the paragraphs that follow I shall make use of the vocabulary employed by Dr. C. D. Broad in The Mind and Its Place in Nature, a book which, for subtlety and exhaustiveness of analysis and limpid clarity of exposition takes rank among the masterpieces of modern philosophical literature.

The process of seeing may be analyzed into three subsidiary processes—a process of sensing, a process of selecting and a process of perceiving.

That which is sensed is a set of sensa within a field. (A visual sensum is one of the coloured patches which form, so to say, the raw material of seeing, and the visual field is the totality of such coloured patches which may be sensed at any given moment.)

Sensing is followed by selecting, a process in which a part of the visual field is discriminated, singled out from the rest. This process has, as its physiological basis, the fact that the eye records its clearest images at the central point of the retina, the macular region with its minute fovea centralis, the point of sharpest vision. There is also, of course, a psychological basis for selection; for on any given occasion there is generally something in the visual field which it is in our interest to discriminate more clearly than any other part of the field.

The final process is that of perceiving. This process entails the recognition of the sensed and selected sensum as the appearance of a physical object existing in the external world. It is important to remember that physical objects are not given as primary data. What is given is only a set of sensa; and a sensum, in Dr. Broad’s language, is something “non-referential.” In other words, the sensum, as such, is a mere coloured patch having no reference to an external physical object. The external physical object makes its appearance only when we have discriminatively selected the sensum and used it to perceive with. It is our minds which interpret the sensum as the appearance of a physical object out in space.

It is clear from the behaviour of infants that we do not enter the world with full-fledged perceptions of objects. The new-born child starts by sensing a mass of vague, indeterminate sensa, which it does not even select, much less perceive as physical objects. Little by little, it learns to discriminate the sensa that have, for its particular purposes, the greatest interest and significance, and with these selected sensa it gradually comes, through a process of suitable interpretation, to perceive external objects. This faculty for interpreting sensa in terms of external physical objects is probably inborn; but it requires, for its adequate manifestation, a store of accumulated experiences and a memory capable of retaining such a store. The interpretation of sensa in terms of physical objects becomes rapid and automatic only when the mind can draw on its past experience of similar sensa successfully interpreted in a similar way.

In adults, the three processes of sensing, selecting and perceiving are for all intents and purposes simultaneous. We are aware only of the total process of seeing objects, and not of the subsidiary processes which culminate in seeing. It is possible, by inhibiting the activity of the interpreting mind, to catch a hint of the raw sensum, as it presents itself to the eyes of the new-born child. But such hints are very imperfect at the best, and of brief duration. For the adult, a complete recapture of the experience of pure sensation, without perception of physical objects, is possible, in most cases, only in certain abnormal conditions, when the upper levels of the mind have been put out of action by drugs or disease. Such experiences cannot be introspected while they are going on; but they can often be remembered, when the mind has recovered its normal condition. By calling up these memories, we can provide ourselves with an actual picture of those processes of sensing, selecting and perceiving, which culminate in the end-process of seeing physical objects in the external world.

An Illustration

Here, by way of example, is an account of an experience of my own, while “coming out” of an anaesthetic administered in the dentist’s chair. Returning awareness began with pure visual sensations completely devoid of significance. These, as I can remember them, were not of objects existing “out there” in the familiar, three-dimensional world of everyday experience. They were just coloured patches, existing in and for themselves, unrelated not only to the external world, but also to myself—for the knowledge of self was still wholly lacking, and these meaningless and unattached sense impressions were not mine; they simply were. This kind of awareness lasted for a minute or two; then the effect of the anaesthetic wore off a little further, a notable change took place. The coloured patches were no longer sensed merely as coloured patches, but became associated with certain objects “out there” in the external three-dimensional world—specifically, the façades of houses seen through the window facing the chair in which I was reclining. Attention travelled across the visual field selecting successive parts of it and perceiving these selected parts as physical objects. From being vague and meaningless, the sensa had developed into manifestations of definite things belonging to a familiar category and situated in a familiar world of solid objects. Thus recognized and classified, these perceptions (I do not call them “my” perceptions, for “I” had not yet made my appearance on the scene) became immediately clearer, while all sorts of details, unnoticed so long as the sensa lacked significance, were now perceived and evaluated. That which was now being apprehended was no longer a set of mere coloured patches, but a set of aspects of the known, because remembered, world. Known and remembered by whom? For a time there was no indication of an answer. But after a little while, imperceptibly, there emerged myself, the subject of the experience. And with this emergence there came, as I remember, a further clarification of vision. What had been at first raw sensa and had then become, by interpretation, the appearances of known varieties of objects, underwent a further transformation and became objects consciously related to a self, an organized pattern of memories, habits and desires. By becoming related to the self, the perceived objects became more visible, inasmuch as the self, to which they had now entered into relation, was interested in more aspects of external reality than had been the merely physiological being which had sensed the coloured patches, and the more developed, but still un-self-conscious being which had perceived these sensa as appearances of familiar objects “out there” in a familiar kind of world. “I” had now returned; and since “I” happened to take an interest in architectural details and their history, the things seen through the window were immediately thought of as a member of a new category—not merely as houses, but as houses of a particular style and date, and as such possessed of distinguishing characteristics which, when looked for, could be seen even by eyes as inadequate as my own then were. These distinguishing characteristics were now perceived, not because my eyes had suddenly improved, but simply because my mind was once more in a condition to look for them and register their significance.

I have dwelt at some length on this experience, not because it is in any way remarkable or strange, but simply because it illustrates certain facts which every student of the art of seeing must constantly bear in mind. These facts may be formulated as follows.

Sensing is not the same as perceiving.

The eyes and nervous system do the sensing, the mind does the perceiving.

The faculty of perceiving is related to the individual’s accumulated experiences, in other words, to memory.

Clear seeing is the product of accurate sensing and correct perceiving.

Any improvement in the power of perceiving tends to be accompanied by an improvement in the power of sensing and of that product of sensing and perceiving which is seeing.

Perception Determined by Memory

The fact that heightened powers of perception tend to improve the individual’s capacity for sensing and seeing is demonstrated, not merely under such abnormal circumstances as I have described, but in the most ordinary activities of everyday life. The experienced microscopist will see certain details on a slide; the novice will fail to see them. Walking through a wood, a city dweller will be blind to a multitude of things which the trained naturalist will see without difficulty. At sea, the sailor will detect distant objects which, for the landsman, are simply not there at all. And so on, indefinitely. In all such cases improved sensing and seeing are the result of heightened powers of perceiving, themselves due to the memory of similar situations in the past. In the orthodox treatment of defective vision attention is paid to only one element in the total process of seeing, namely the physiological mechanism of the sensing apparatus. Perception and the capacity to remember, upon which perception depends, are completely ignored. Why and with what theoretical justification, goodness only knows. For in view of the enormous part which mind is known to play in the total process of seeing, it seems obvious that any adequate and genuinely aetiological treatment of defective vision must take account, not only of sensing but also of the process of perceiving, as well as that other process of remembering, without which perceiving is impossible. It is a highly significant fact that, in Dr. Bates’s method for re-educating sufferers from defective vision, these mental elements in the total process of seeing are not neglected. On the contrary, many of his most valuable techniques are directed specifically to the improvement of perception and of that necessary condition of perception, memory.