C.

THE THEORY OF VISION VINDICATED.

EXPERIENCE OF PERSONS BORN BLIND.

In the last Section of the Vindication (p. 299), Berkeley refers to the now well-known experiment of Chesselden, in which sight was given to a boy born blind. As this case is described imperfectly in the Vindication, and as it is often referred to in the controversy as to whether our power of interpreting the tactual, muscular, and locomotive meaning of visual signs is, on the one hand, original and instinctive, or, on the other hand, the acquired result of mental association and habit, I here reprint the entire Communication, given in the Philos. Trans., No. 402 :—

'An account of some observations made by a young gentleman, who was born blind, or who lost his sight so early, that he had no remembrance of ever having seen, and was couched between 13 and 14 years of age. By Mr. Will. Chesselden, F.R.S., Surgeon to Her Majesty, and to St. Thomas's Hospital.

Tho' we say of the gentleman that he was blind, 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 anything;-for the light by which these perceptions are made, being let in obliquely through the aqueous humour, or the anterior surface of the chrystalline (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 thro' 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 discern'd, tho' the colour may. And thus it was with this young gentleman, who though he knew these colours asunder in a good light, yet when he saw them after he was couch'd, 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. Now scarlet he thought the most beautiful of all colours, and of others the most gay were the most pleasing, whereas the first time he saw black, it gave him great uneasiness, yet after a little time he was reconcil'd to it; but some months after, seeing by accident a Negroe woman, he was struck with great horror at the sight.

When he first saw, he was so far from making any judgment about distances, that he thought all objects whatever touched his eyes (as he express'd it) as what he felt did his skin; and thought no objects. so agreeable as those which were smooth and regular, tho' 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 anything, nor any one thing from another, however different in shape or magnitude; but upon being told what things were, whose form he knew before from feeling, he would carefully observe, that he might know them again; but, having too many objects to learn at once, he forgot many of them; and (as he said) at first he learn'd to know, and again forgot a thousand things in a day. One particular only (tho' it may appear trifling) I will relate—having forgot which was the cat and which the dog, he was asham'd to ask; but catching the cat (which he knew by feeling) he was observ'd to look at her steadfastly, and then setting her down, said, So, Puss! I shall know you another time.' He was very much surpris'd that those things which he had lik'd best did not appear most agreeable to his eyes, expecting those persons would appear most beautiful that he lov'd most, and such things to be most agreeable to his sight that were so to his taste. We thought he soon knew what pictures represented which were shew'd to him, but we found afterwards we were mistaken; for about two months after he was couch'd, he discovered at once, they represented solid bodies; when to that time he consider'd them only as party-colour'd planes or surfaces diversified with variety of paint; but even then he was no less surpris'd, 'expecting the pictures would feel like the things they represented, and was amaz'd when he found those parts, which by their light and shadow appear'd now round and uneven, felt only flat like the rest; and ask'd which was the lying sense,-feeling or seeing?

Being shewn his father's picture in a locket at his mother's watch, and told what it was, he acknowledged a likeness, but was vastly surpris'd; asking how it could be that a large face could be express'd in so little room, saying, it should have seem'd as impossible to him as to put a bushel of anything into a pint.

At first he could bear but very little sight, and the things he saw he thought extreamly large; but upon seeing things larger, those first seen he conceiv'd less, never being able to imagine any lines beyond the bounds he saw; the room he was in, he said, he knew to be but part of the house, yet he could not conceive that the whole house could look bigger. Before he was couch'd he expected little advantage from seeing, worth undergoing an operation for, except reading and

writing; for he said he thought he could have no more pleasure in walking abroad than he had in the garden, which he could do safely and readily. And even blindness, he observ'd, had this advantage, that he could go anywhere in the dark much better than those who can see; and after he had seen, he did not soon lose this quality, nor desire a light to go about the house in the night. He said every new object was a new delight, and the pleasure was so great that he wanted ways to express it; but his gratitude to his operator he could not conceal, never seeing him for some time without tears of joy in his eyes, and other marks of affection: and if he did not happen to come at any time when he was expected, he would be so griev'd that he could not forbear crying at his disappointment. A year after first seeing, being carried upon Epsom Downs, and observing a large prospect, he was exceedingly delighted with it, and called it a new kind of seeing. And now being lately couch'd of his other eye, he says that objects at first appeared large to this eye, but not so large as they did at first to the other; and looking upon the same object with both eyes, he thought it look'd about twice as large as with the first couch'd eye only, but not double, that we can anyways discover.'

No very satisfactory inference can be drawn from a narrative so deficient in the refinement of thought and expression which the subject requires. The question is too subtle for experiments conducted in this fashion. Nor can more be said in favour of a succession of somewhat similar experiments recorded in the Philosophical Transactions. The most important are the following:

1. Case described by Mr. Ware, Surgeon, in the Philos. Trans. (1801).

2. Two cases described by Mr. Home, in the Philos. Trans. (1807). 3. Case of the lady described by Mr. Wardrop, Surgeon, in the Philos. Trans. (1826).

To these may be added Stewart's 'Account of James Mitchell, a boy born deaf and blind,' in the seventh volume of the Transactions of the Royal Society of Edinburgh. See Hamilton's Edition of Stewart's Works, Vol. III. Appendix, pp. 300—370; also p. 388.

As I have quoted one of the earliest described cases-that of Chesselden, I shall end by giving the following, which is one of the last and most philosophically described of any I have met with. It is contained in Mr. Nunnely's valuable scientific treatise on The Organs of Vision: their Anatomy and Physiology (1858):

'The case was that of a fine and most intelligent boy, nine years of age, who had congenital cataract of both eyes, in whom the retina was more perfect than it commonly is at so advanced an age, as shown

by the excellent sight he subsequently acquired. He had always lived in a very large manufacturing village, about sixteen miles from Leeds. He could find his way all about this place. Walking along the middle of the road, when he heard any object approaching, he at once stopped, groped his way to the side of the road, and remained perfectly still until it had passed. Any one whom he knew he was able to recognise by the sound of the voice, and by passing his hands over the face and body of the person. He could perceive the difference between a bright, sunny, and a dark, cloudy day, and could follow the motions. of a candle without discerning what it was. He had been sent to school for some time, and by means of models and a raised alphabet, could by touch alone arrange the different letters into short words. I presented to him in succession a great number of different objects, each one of which he took into both hands, felt it most carefully over with both, then with equal minuteness with one, turning the object over and over again, in every direction; the tongue was next applied to it; and lastly, he applied it so near to the eye as to touch the eyelids, when he pronounced his opinion upon it, and generally with correctness, as to the nature and form of the object, when these were distinct. Thus he recognised books, stones, small boxes, pieces of wood and bone of different shapes, a broken piece of hard biscuit. A cube and a sphere he could readily recognise, saying the one was square and the other round, and that both were made of wood; but a sphere which was made of perfectly smooth, hard wood, he was very confident was bone. In an object where the angles were not very distinct, he made constant mistakes in the shape, first saying that it was square, then that it was round. Very bright light colours, when touching the eyelids, he could at once recognise, calling them all white; all dull and dark colours he said were black. Between a thin circle of wood and a sphere or a cube he instantly decided by the hand alone. On putting half-a-crown piece into his hands he immediately said it was money, but for long was undecided whether it was half-a-crown or a penny; however, after carefully turning it over for some time, so as frequently to bring every part into contact with the hand, then putting it to the tongue, and afterwards so close to the eye that it touched the eyeball itself, he said decidedly, "It is half-a-crown."

The lenses were very large, milky, with caseous particles, quite white and opaque, the capsules being clear and transparent. As is well known, in most cases, before this period of life, the lens itself has been absorbed, leaving only a leathery, opaque capsule, and, of course, not nearly so favourable for such observations as this one. After keeping him in a dark room for a few days, until the opaque particles of lenses were nearly absorbed, and the eyes clear, the same objects, which had been kept carefully from him, were again presented to his notice. He could at once perceive a difference in their shapes; though he could not in the least say which was the cube and which the sphere, he saw, they were not of the same figure. It was not until they had many times been placed in his hands that he learnt to distinguish by the eye the one which he had just had in his hands, from the other placed beside

it. He gradually became more correct in his perception, but it was only after several days that he could or would tell by the eyes alone, which was the sphere and which the cube; when asked, he always. before answering, wished to take both into his hands; even when this was allowed, when immediately afterwards the objects were placed before the eyes, he was not certain of the figure. Of distance he had not the least conception. He said everything touched his eyes, and walked most carefully about, with his hands held out before him, to prevent things hurting his eyes by touching them. Great care was requisite to prevent him falling over objects, or walking against them. Improvement gradually went on, and his subsequent sight was, and now is, comparatively perfect.'

None of these experiments, taken by themselves, unequivocally determine the question-Whether the power of interpreting the visual signs of real or tangible extension is inspired, or is, on the contrary, acquired by association and constructive activity of intellect. But they confirm the conclusion, that visible signs are not less indispensable to an imagination of trinal extension than the artificial signs of language are necessary to abstract thought and reasoning-that one born blind can have only a vague perception of an external world. Moreover, when once we are experimentally acquainted with distances, a mathematical analysis of the perspective lines leading from any object to the eye is possible, with an involved sense of necessity, which seems to presuppose relations common to the visible signs and the felt reality. The difficulty which confronts Berkeley is, that on his theory space and its mathematical relations are relative to sensations which, per se, are contingent and phenomenal, and thus wanting in the element which alone gives abso- . lute stability to mathematical science: quantitative infinity disappears, and space and its relations are the real but arbitrary results of creation or the voluntary activity of God.