As we frequently ascribe to the objects of Sight a magnitude and proportion which does not really belong to them, but to the objects of 456 Touch which they represent, so we likewise ascribe to them a steadiness of appearance, which as little belongs to them, but which they derive altogether from their connection with the same objects of Touch. The chair which now stands at the farther end of the room, I am apt to imagine, appears to my eye as large as it did when it stood close by me, when it was seen under angles at least four times larger than those under which it is seen at present, and when it must have occupied, at least, sixteen times that portion which it occupies at present, of the visible plain or surface which is now before my eyes. But as I know that the magnitude of the tangible and represented chair, the principal object of my attention, is the same in both situations, I ascribe to the visible and representing chair (though now reduced to less than the sixteenth part of its former dimensions) a steadiness of appearance, which certainly belongs not in any respect to it, but altogether to the tangible and represented one. As we approach to, or retire from, the tangible object which any visible one represents, the visible object gradually augments in the one case, and diminishes in the other. To speak accurately, it is not the same visible object which we see at different distances, but a succession of visible objects, which, though they all resemble one another, those especially which follow near after one another; yet are all really different and distinct. But as we know that the tangible object which they represent remains always the same, we ascribe to them too a sameness which belongs altogether to it: and we fancy that we see the same tree at a mile, at half a mile, and at a few yards distance. At those different distances, however, the visible objects are so very widely different, that we are sensible of a change in their appearance. But still, as the tangible objects which they represent remain invariably the same, we ascribe a sort of sameness even to them too.
It has been said, that no man ever saw the same visible object twice; and this, though, no doubt, an exaggeration, is, in reality, much less so than at first view it appears to be. Though I am apt to fancy that all the chairs and tables, and other little pieces of furniture in the room where I am sitting, appear to my eye always the same, yet their appearance is in reality continually varying, not only according to every variation in their situation and distance with regard to where I am sitting, but according to every, even the most insensible variation in the altitude of my body, in the movement of my head, or even in that of my eyes. The perspective necessarily varies according to all even the smallest of these variations; and consequently the appearance of the objects which that perspective presents to me. Observe what difficulty a portrait painter finds, in getting the person who sits for his picture to present to him precisely that view of the countenance from which the first outline was drawn. The painter is scarce ever completely satisfied with the situation of the face which is presented to 457 him, and finds that it is scarcely ever precisely the same with that from which he rapidly sketched the first outline. He endeavours, as well as he can, to correct the difference from memory, from fancy, and from a sort of art of approximation, by which he strives to express as nearly as he can, the ordinary effect of the look, air, and character of the person whose picture he is drawing. The person who draws from a statue, which is altogether immovable, feels a difficulty, though, no doubt, in a less degree, of the same kind. It arises altogether from the difficulty which he finds in placing his own eye precisely in the same situation during the whole time which he employs in completing his drawing. This difficulty is more than doubled upon the painter who draws from a living subject. The statue never is the cause of any variation or unsteadiness in its own appearance. The living subject frequently is.
The benevolent purpose of nature in bestowing upon us the sense of seeing, is evidently to inform us concerning the situation and distance of the tangible objects which surround us. Upon the knowledge of this distance and situation depends the whole conduct of human life, in the most trifling as well as in the most important transactions. Even animal motion depends upon it; and without it we could neither move, nor even sit still, with complete security. The objects of sight, as Dr. Berkley finely observes, constitute a sort of language which the Author of Nature addresses to our eyes, and by which he informs us of many things, which it is of the utmost importance to us to know. As, in common language, the words or sounds bear no resemblance to the thing which they denote, so, in this other language, the visible objects bear no sort of resemblance to the tangible object which they represent, and of whose relative situation, with regard both to ourselves and to one another, they inform us.
He acknowledges, however, that though scarcely any word be by nature better fitted to express one meaning than any other meaning, yet that certain visible objects are better fitted than others to represent certain tangible objects. A visible square, for example, is better fitted than a visible circle to represent a tangible square. There is, perhaps, strictly speaking, no such thing as either a visible cube, or a visible globe, the objects of sight being all naturally presented to the eye as upon one surface. But still there are certain combinations of colours which are fitted to represent to the eye, both the near and the distant, both the advancing and the receding lines, angles, and surfaces of the tangible cube; and there are others fitted to represent, in the same manner, both the near and the receding surface of the tangible globe. The combination which represents the tangible cube, would not be fit to represent the tangible globe; and that which represents the tangible globe, would not be fit to represent the tangible cube. Though there may, therefore, be no resemblance between visible and tangible 458 objects, there seems to be some affinity or correspondence between them sufficient to make each visible object fitter to represent a certain precise tangible object than any other tangible object. But the greater part of words seem to have no sort of affinity or correspondence with the meanings or ideas which they express; and if custom had so ordered it, they might with equal propriety have been made use of to express any other meanings or ideas.
Dr. Berkley, with that happiness of illustration which scarcely ever deserts him, remarks, that this in reality is no more than what happens in common language; and that though letters bear no sort of resemblance to the words which they denote, yet that the same combination of letters which represents one word, would not always be fit to represent another; and that each word is always best represented by its own proper combination of letters. The comparison, however, it must be observed, is here totally changed. The connection between visible and tangible objects was first illustrated by comparing it with that between spoken language and the meanings or ideas which spoken language suggests to us; and it is now illustrated by the connection between written language and spoken language, which is altogether different. Even this second illustration, besides, will not apply perfectly to the case. When custom, indeed has perfectly ascertained the powers of each letter; when it has ascertained, for example, that the first letter of the alphabet shall always represent such a sound, and the second letter such another sound; each word comes then to be more properly represented by one certain combination of written letters or characters, than it could be by any other combination. But still the characters themselves are altogether arbitrary, and have no sort of affinity or correspondence with the articulate sounds which they denote. The character which marks the first letter of the alphabet, for example, if custom had so ordered it, might, with perfect propriety, have been made use of to express the sound which we now annex to the second, and the character of the second to express that which we now annex to the first. But the visible characters which represent to our eyes the tangible globe, could not so well represent the tangible cube; nor could those which represent the tangible cube, so properly represent the tangible globe. There is evidently, therefore, a certain affinity and correspondence between each visible object and the precise tangible object represented by it, much superior to what takes place either between written and spoken language, or between spoken language and the ideas or meanings which it suggests. The language which nature addresses to our eyes, has evidently a fitness of representation, an aptitude for signifying the precise things which it denotes, much superior to that of any of the artificial languages which human art and ingenuity have ever been able to invent.
459 That this affinity and correspondence, however, between visible and tangible objects could not alone, and without the assistance of observation and experience, teach us, by any effort of reason, to infer what was the precise tangible object which each visible one represented, if it is not sufficiently evident from what has been already said, it must be completely so from the remarks of Mr. Cheselden upon the young gentleman above-mentioned, whom he had couched for a cataract. ‘Though we say of this gentleman, that he was blind,’ observes Mr. Cheselden, ‘as we do of all people who have ripe cataracts; yet they are never so blind from that cause but that they can discern day from night; and for the most part, in a strong light, distinguish black, white, and scarlet; but they cannot perceive the shape of any thing; for the light by which these perceptions are made, being let in obliquely through aqueous humour, or the anterior surface of the crystalline, (by which the rays cannot be brought into a focus upon the retina,) they can discern in no other manner than a sound eye can through a glass of broken jelly, where a great variety of surfaces so differently refract the light, that the several distinct pencils of rays cannot be collected by the eye into their proper foci; wherefore the shape of an object in such a case cannot be at all discerned though the colour may: and thus it was with this young gentleman, who, though he knew those colours asunder in a good light, yet when he saw them after he was couched, the faint ideas he had of them before were not sufficient for him to know them by afterwards; and therefore he did not think them the same which he had before known by those names.’ This young gentleman, therefore, had some advantage over one who from a state of total blindness had been made for the first time to see. He had some imperfect notion of the distinction of colours; and he must have known that those colours had some sort of connection with the tangible objects which he had been accustomed to feel. But had he emerged from total blindness, he could have learnt this connection only from a very long course of observation and experience. How little this advantage availed him, however, we may learn partly from the passages of Mr. Cheselden’s narrative, already quoted, and still more from the following:
‘When he first saw,’ says that ingenious operator, ‘he was so far from making any judgment about distances, that he thought all objects whatever touched his eyes (as he expressed) as what he felt did his skin; and thought no objects so agreeable as those which were smooth and regular, though he could form no judgment of their shape, or guess what it was in any object that was pleasing to him. He knew not the shape of any thing, nor any one thing from another, however different in shape or magnitude; but upon being told what things were, whose form he before knew from feeling, he would carefully observe, that he might know them again; but having too many 460 objects to learn at once, he forgot many of them; and (as he said) at first learned to know, and again forgot a thousand things in a day. One particular only (though it may appear trifling) I will relate: Having often forgot which was the cat and which was the dog, he was ashamed to ask; but catching the cat (which he knew by feeling) he was observed to look at her steadfastly, and then setting her down, said, So, puss! I shall know you another time.’
When the young gentleman said, that the objects which he saw touched his eyes, he certainly could not mean that they pressed upon or resisted his eyes; for the objects of sight never act upon the organ in any way that resembles pressure or resistance. He could mean no more than that they were close upon his eyes, or, to speak more properly, perhaps, that they were in his eyes. A deaf man, who was made all at once to hear, might in the same manner naturally enough say, that the sounds which he heard touched his ears, meaning that he felt them as close upon his ears, or, to speak perhaps more properly, as in his ears.
Mr. Cheselden adds afterwards: ‘We thought he soon knew what pictures represented which were showed to him, but we found afterwards we were mistaken; for about two months after he was couched, he discovered at once they represented solid bodies, when to that time, he considered them only as party-coloured planes, or surfaces diversified with variety of paints; but even then he was no less surprised, expecting the pictures would feel like the things they represented, and was amazed when he found those parts, which by their light and shadow appeared now round and uneven, felt only flat like the rest; and asked which was the lying sense, feeling or seeing?’
Painting, though, by combinations of light and shade, similar to those which Nature makes use of in the visible objects which she presents to our eyes, it endeavours to imitate those objects; yet it never has been able to equal the perspective of Nature, or to give to its productions that force and distinctness of relief and rejection which Nature bestows upon hers. When the young gentleman was just beginning to understand the strong and distinct perspective of Nature, the faint and feeble perspective of Painting made no impression upon him, and the picture appeared to him what it really was, a plain surface bedaubed with different colours. When he became more familiar with the perspective of Nature, the inferiority of that of Painting did not hinder him from discovering its resemblance to that of Nature. In the perspective of Nature, he had always found that the situation and distance of the tangible and represented objects, corresponded exactly to what the visible and representing ones suggested to him. He expected to find the same thing in the similar, though inferior perspective of Painting, and was disappointed when he found that the visible and tangible objects had not, in this case, their usual correspondence.