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Of the Evidence of Experience.
In the first place, experience, commencing in the simplest perceptions of sense and consciousness, and terminating in the most important and interesting conclusions of the inductive philosophy, is the first ground of human knowledge. It is wonderful to reflect upon how little is done for us by nature, in the matter of extending our acquaintance with things, and what vast acquisitions she has placed it in our power to make for ourselves. To begin with the senses. Our simple perceptions introduced by cach sense, are almost reduced to an unit, our acquired perceptions form a sufficiently ample basis, on which to erect the vast and magnificent structure of human science and philosophy. To commence with the first and most simple elements of our knowledge. Suppose our philosopher to be in the state in which Adam was, when he rose in the full perfection of his powers, under the hands of his Creator, but uninstructed by him, and having every thing to learn of himself. Suppose him with all his faculties, external and internal, to commence his acquaintance with the objects around him. Sounds are wafted to his ears, and odours to his nostril, but he is uncertain that they proceed from any object exterior to himself, and concludes that they are mere sensations in himself, or modifications of his former conscious being. Let us suppose him next, to open his eyes upon surrounding objects. Light enters into them, but as the muscles connected with the pupil, have as yet been untaught to perform their office, he is unable to contract and dilate it, so as to receive upon the retina, the due proportion of rays, he is therefore dazzled and pained, and soon relieves himself by closing the lids. In a short time, however, guided by instinct, and yielding to the force of nature, the muscles learn to execute their functions, and he is able to contemplate the objects that present themselves, Still he is unable to distinguish any thing but a plain surface, variously coloured, every thing appearing equally remote, or rather equally present, and to press upon his eye, and he cannot discriminate the smallest from the largest objects. This theory has been abundantly substantiated by fact and experiment. The man who was born blind, and couched in mature age by Cheselden, a distinguished English surgeon, declared that at first every thing seemed to touch his eye; and I am informed, that a woman in Pennsylvania, who, after her marriage had the cataracts removed from both her eyes, gives her testimony in confirmation of the same doctrine. The physician who performed the operation reports, that when her sight was restored, she declared that her sensations were indescribably delightful, but at the same time, her newly recovered power of vision was for some time, of very little use to her. She was perpetually stretching out her hands, from fear of running against objects, being unable to distinguish their distances or magnitudes; and when her own husband came into the room, she knew nothing of him until he spoke, and she recognized the voice to which she had become accustomed. Both Dr. Reid and Condillac, ascribe to Bishop Berkeley the merit of having first discovered that extension, figure, and space, are originally perceived by the sense of touch only, and not by sight; but, at the same time, that we would detract nothing from the merit of that great man, is not the same doctrine evidently held in that part of Mr. Locke's work, in which he undertakes to give a solution of the problem proposed to him, by his friend Molineux? The problem is this—“Suppose a man born blind, and now adult, and taught by his touch to distinguish hetween a cube and a sphere of the same metal, and nighly I agree with
of the same bigness, so as to tell when he felt one and tother, which is the cube, which is the sphere. Suppose, then, the cube and sphere placed on a table, and the blind man to be made to see. Quere, whether by his sight; before he touched them, he could now distinguish and tell which is the globe, which the cube. To which the acute and judicious proposer answers, not. For though he has attained the ex. perience of how a globe, how a cube affects his touch, yet he has not yet attained the experience, that what affects his touch so or so, must affect his sight so or so; or that a pro. tuberant angle in the cube, that pressed his hand unequally, shall appear to his eye as it does in the cube. I this thinking gentleman, continues Mr. Locke, whom I am proud to call my friend, in his answer to this his problem; and am of opinion, that the blind man at first sight, would not be able to say with certainty, which was the globe, which the cube, whilst he only saw them; though he could unerringly name them by his touch, and certainly distinguish them by the difference of their figures felt. This I have set down, and leave with my reader, as an occasion for him to consider, how much be may be beholden to experience, improvement, and acquired notions, where he thinks he has not the least use of, or help from them; and the rather, because this observing gentleman further adds, that having upon the occasion of my book, proposed this to divers very ingenious men, he hardly ever met with one, that at first gave the answer to it, which he thinks true, till by hearing his reasons they were convinced.” In giving a solution to this problem, which subsequent experiments have completely confirmed, Mr. Locke not only discovered his deep insight into this part of our nature, prior to any experiments made upon the subject, for he refers to none; but at the same time, led the way to all those discoveries, which have been since made in regard to the original and acquired perceptions, not of sight only, but also of all the senses, If he did not explore the whole field afterwards traversed by Bishop Berkeley, he here puts into his hand the key that led him and subsequent inquirers, into the deep mysteries of our original perceptions.
Mr. Cheselden's account of the observations made by a young man, who was couched by him in his thirteenth year, is so curious and interesting, that it may be worth while to transcribe the most important particulars contained in it. “Though we say of this gentleman,” says Cheselden, “ that he was born 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 any thing: for the light by which these perceptions are made, being let in obliquely through the aqueous humour, or the anterior surface of the chrystaline, by which the rays cannot be brought in 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 these 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. 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 reconciled to it: but some months after seeing by accident a negro 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 expressed it, 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 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 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 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. He was very much surprised that those things which he had liked best, did not appear most agreeable to his eyes, expecting those persons would appear most beautiful that he loved 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 showed to him, but we found afterwards we were mistaken; for about two months after he was couched, he discovered at once that they represented solid bodies; when to that time he considered them only as party-coloured planes, or surfaces diversified with variety of paint; 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? Being shown his father's picture in a locket at his mother's watch, and told what it was, he acknowledged a likeness, but was vastly surprised, asking how