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rect views of the matter of education, will never regard it as a subject of boasting, or a ground of future expectation, that by this hot-bed kind of process, their offspring have been able to a tain to a proficiency in learning, which awakes the surprise aad astonishment of the vulgar. Those lessons, which are at this very early period attained with infinite toil and difficulty, and perhaps with the loss of health and comfort, at a more mature age would come to them almost un. sought. Let nature, therefore, the kindest and most indulgent of all mistresses, be their instructress, who so gently mixes the agreeable with the useful, and let the only lessons which are imbibed at this early period, be derived from her universal school.
But to return from this short digression to the subject of our acquired perceptions. On the subject of the acquired perceptions of sight, several questions have been raised. In the first place, it is asked, whether we do not originally perceive objects in an inverted position, as the image upon
the tunica retina is known to be inverted? And whether, of consequence, our seeing them erect is not an acquired perception?
As soon as it was discovered by Kepler that in our per. ception of the objects of sight, the image upon the retina is inverted instead of being erect, this was a natural inquiry in philosophy. In order to render the subject as clear as possible to the reader, we will suppose a small table A with a globe B resting upon it, placed in view of a man who has never before seen, but has just been couched by the surgeon. Now, the question is, since the globe B will be below the table A in the image upon the retina, whether it would appear, at first, to be really below it in external nature? We have before stated the appearance which an object of this nature would present to a man under these circumstances; viz. that of a plain superficies variously coloured, as he would have no idea of distances, figures, or magnitudes. Supposing, then, the globe B, and the table A to be black, and before a white wall, all that the newly couched observer would be able to distinguish, would be such a form as would be made by the globe and table, if painted in black upon white canvass. To simplify the query, then: On this white canvass would our observer seem to see the globe resting below the table, according to the position of the image upon the retina, or above it as it exists in nature? Bishop Berkeley, with his usual refinement and subtilty, would say, that our ideas of upper and under are merely relative; and we call that upper which, when examined by the touch, is above the earth, and that under, which when examined by the same sense, is nearest to the earth. Now as the perceptions of sight have no resemblance to those of touch, we could form no idea originally, when we perceived any thing by the eyes, whether one part was under, and the other above, according to the previous decisions of the sense of touch, The only way, therefore, that we could obtain, by sight, ideas of what our sense of touch had taught us as above and below, would be, by marking the appearances which the higher and lower parts of objects display, and then, when those appearances are again exhibited, we shall be able to recognize them. Thus, for instance, noticing the peculiar appearances exhibited to us by the globe and the table, and observing by the touch at the same time, that the one is placed above the other, whenever the same appearance is presented to the eye, we at once know that the one is above, and the other below, or the one the farthest from the earth, and the other the nearest to it.
This solution is of a piece with Bishop Berkeley's system and views of things, and may be justly applied in explaining the phenomena of all our acquired perceptions of sight. But it seems to leave entirely out of the account, that we must have some original perceptions of sight as well as touch, and of course does not solve the phenomenon in question. Nothing can be more certain, according to the principles we have before stated, and proved from experiment and observation, than that by our sight we should at first be unable to decide which was the globe, and which the table, as before ascertained by our touch, the case being the same stated by Molineaux to Mr. Locke, since there can be no kind of resemblance between the perceptions of touch and those of sight; but, at the same time, it is not to be denied, that we should have original perceptions by sight of the globe and table, as distinct from each other, as those which we had of them by the touch.* In other words,
In other words, the appearance which
Mr. Jurin, in his remarks upon Article 132, of Dr. Smith's opticks, speaking of the problem proposed by Molineaux to Mr. Locke, maintains, that Mr. Locke was right in deciding that a blind man who bad known a globe and a cube only by his touch, if suddenly restored to sight, would not be able at once, to determine which was the globe and which the cube; but thinks, that without touching them, if they were presented to his view, and he was told that they were a globe and cube, he would be able to distinguish the one from the other. The process of reasoning by which Mr. Jurin thinks the blind man would be able by sight alone to determine which was the globe, and which the cube, is in substance this: that the blind man when he went around the globe, and viewed it on all sides would find that it affected his sense in the same way, while the cube would differently affect his sense according to the position from which he viewed it. Now, upon reflection, he would recollect that the same effect had been produced upon his sense of touch, the globe producing always the same sensation, while the cube differently affected him. Hence he would conclude, that the one wbich produced one invariable sensation by means of the eye, must be the same as that which produced an invariable sensation by means of touch.” I am inclined to think that this view of the subject is mistaken. It is true, as we have asserted in the text, that the sensation produced by the globe, and that produced by the cube through the organs of vision, would be different; and if any other person should inform the man, thus restored to sight, that the figure which presented a regular curvature was the globe, and that which varied in appearance was the cube, he would ever after be able to distinguish them from each other by sight alone. But unless he received the information from some other person, or actually touched the objects, and compared his sensations of sight and touch together, and discovered by examination, that the object which to
the globe presented to the eye would be as diverse and distinct from that presented by the table, as the figure of the one, when handled and examined by the sense of feeling, would be from that of the other. Besides, although it be strictly just and philosophical to assert, that there is really no resemblance between the perceptions of sight, and those of touch; yet there would be so far a congruity or correspondence between them, that it would be utterly impossible, that the same object which presented to the feeling the sharp angles and projecting points of the table, should exhibit to the eye the regular curvature, and smooth surface of the globe. Froin these observations,
bservations, I think, it must appear evident that, if in our first impressions, we perceived by our sight the globe below the table instead of being above it, as it is found in nature, when we came to compare together our perceptions of sight with those of touch, we should be able to determine that it was so. Now, from the experience of those who have been couched, it has been ascertained, that although the image painted upon the retina is inverted, yet the object is invariably perceived from the first in an erect position. Not one of them could ever discover that the object appeared inverted. The original question, therefore, again recurs to be solved, if soluble, by philosophy. How it happens that we perceive objects erect
his touch appeared to be a globe exhibited such a peculiar appearance to the eye, and so of the cube, he never would be able to discriminate them. How could he know, according to Mr. Jurin's opinion, that the same thing which occasioned one uniform sensation to the sight, would occasion a uniform and invariable sensation to the touch? For ought he could know, that object wbich occasioned the same sensation always to the eye, might have been the one which occasioned such a variety of sensations to the touch. He might, indeed, if we suppose him coolly to reason and philosophise on the subject, make the similarity of perception in both cases a ground of conjecture that they were occasioned by the same object, but never a ground of demonstration or entire certainty.
when the images of them painted upon the retina is evidently inverted?
In order that we may have clear and distinct ideas on this point, I would remark, that we should keep constantly in view the nature of perception, that it is an act of the mind and not of the body, although it is undoubtedly produced by the instrumentality, and through the intermediation of the external organs of sense. By the very terms in which the proposition is enunciated, it would appear as if the difficulty is occasioned by our imagining the mind to perceive the image upon the retina, and not the outward object itself. Otherwise in what consists the difficulty? We have before seen that the doctrine held on this subject, is, that rays of light pass from the object to the eye, and being refracted by its humours and the christaline lens, form an image upon the retina, and by means of some motions, or some action communicated to the nervous coat and the brain, enable us to perceive it. The formation of an inverted image at the bottom of the eye, is, therefore, nothing more than a part of that train of action in the system to which, by the wisdom of the Creator is annexed a perception of the mind. Now we know that it is a mystery, unsearchable to the human understanding, how any action upon a system of bodily organs could occasion a perception in the mind; but what has the mind to do with an erect or inverted image? Is not the effect the same upon the mind, whether the action be produced upon the lower part of the eye or the upper? Has the mind an upper and lower part? But the mind while connected with the body, is dependent upon it for its informations of this nature, and must be governed by those laws that influence the operations of body. True. And we have only to determine, according to what law we see objects through the instrumentality of the organ of the eye, to render this whole matter extremely clear. Now we know that, except in cases of optical delusions, we always see objects by