all other passions which quicken or retard the feeling of time. It is just the same with the cubical magnitudes of bodies. We think we see that a body is thick and round; it is quite certain that we see neither the one nor the other, for the eye can see nothing but plain surfaces; but then we learn from experience that certain different appearances of light or shade upon plain surfaces are constantly connected with those feelings of bodies which we call round and thick, Just in the same manner it is probable that the notions which the ear has of distance and position are entirely the result of experience; and that a person deaf from his birth, and suddenly cured, would be quite ignorant from what quarter, and from what distance, sound originated. Thus we see that the senses soon learn to lay aside their own homely and barren language, and to speak in a more elegant and universal dialect; and we see that man, endowed with the senses he now is, and deprived of the power of connecting their notices together by indissoluble associations, would have risen very little above the rank of the lower animals. All the labours of the human mind point and tend towards the same process which has been carried on in our early infancy with respect to associated sensation,-so to connect together, by copious induction, the sign with the thing signified, that the one may suggest the other with the certainty and velocity of sensation. The phenomena of double vision and inverted images I must, for fear of protracting my lecture too long, entirely pass over; referring those whose curiosity may be excited on these subjects to Bishop Berkeley's Essay on Vision, Dr. Porterfield on the Eye, Dr. Wells' Essay on Vision, and Dr. Reid's admirable first work on the Human Mind. To prove, in some measure, how much of our sight is original, and how much acquired, and to illustrate therefore a great deal of what I have said throughout this lecture, I shall read to you the famous case of a young man born blind, and suddenly restored to his sight by undergoing the operation of couching. A young gentleman, who was born with two cataracts upon each of his eyes, was, in 1728, couched by Mr. Cheselden, and by that means for the first time made to see distinctly. "At first," says the operator, "he could bear but very little light, and the things he "saw he thought extremely large; but upon seeing things larger, those first seen he conceived 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 would look bigger. 66 66 66 66 66 66 66 Though we say of this 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 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 crystalline "humour, by which the rays cannot be brought into a 66 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 discerned at all, 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. 66 66 66 "When he first saw, he was so far from making 66 66 66 66 "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 before knew "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 learned to know, and again forget, 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.' 66 6 "We thought he soon knew what pictures repre"sented which were shown him; but we found after"wards we were mistaken, for, about two months "after he was couched, he discovered at once they represented solid bodies, when to that time he con"sidered them only as party-coloured planes, or "surfaces diversified with variety of paints: but even "then, he was no less surprised, expecting the 66 "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 66 uneven, felt only flat like the rest, and asked "which was the lying sense, feeling or seeing. - "In a year after seeing, the young gentleman being "carried upon Epsom Downs, and observing a large "prospect, he was exceedingly delighted with it, and "called it a new kind of seeing." FRAGMENT OF LECTURE V. ON CONCEPTION. before the mind can gaze upon the scene with any portion of tranquillity and composure. This mistake of conception for sensation is also the best key to the phenomena observed in madness. A madman has the conception of all the pageantry of a court, and so may any man in his senses; the difference is, the one knows it to be only a creation of his mind, the other really believes he sees dukes, and marquises, and all the splendour of a real court. If he is not very far gone, he pays some attention to the objects of sense about him, and tells you that he is confined in this sorry situation by the perfidy and rebellion of his subjects. As the disease further advances, he totally neglects the objects of his senses; does not see that he sleeps on straw and is chained down, but abandons himself wholly to the creations of his mind, and riots in every extravagance of thought. This, though by far the most common species of insanity, is not the only one. There are some persons quite rational in their perceptions, who are considered as deranged only from a morbid association of ideas; as in the instance of the patient mentioned in Mr. Haslam's book, who persevered in a vegetable diet because, he said, roast and boiled meat felt the most exquisite pain while any person was devouring them. The mistaking of conceptions for sensations appears also to be the proper explanation of what passes in our minds during sleep. To consider sleep aright, we must divide it into stages. In profound sleep, there is no evidence that we think at all. When we have been exhausted with great fatigue or acute pain, we often lie motionless for hours, without the smallest recollection that a single idea has past through our minds: the periods of sleeping and waking appear to be consecutive instants of time. In this state of sleep it seems as if every operation of the mind were entirely suspended; and in the instance of those who have taken quantities of opium, or become drowsy from long journeys over snow, it seems to have a great tendency to death. We frequently dream in our sleep without recollecting the slightest feature of our dreams when we awake. It would appear at first, that processes of thought which have made such faint impressions on the memory must have been the slightest and most disconnected of all dreams; and yet the most rational and systematic dreamers - those who walk in their sleep-have seldom or ever the most distant recollection that they have been dreaming at all. In the common state of sleep, where we dream without stirring, or, at least, without walking about, there seems to be, first, a great diminution of the power of the will over the body, but by no means a total suspension of that power: for a person much agitated in his dreams can cry out, and therefore subject the organs of speech to his will; or he can toss about his hands and feet, and so subject those parts of his body to his will; but, however, the influence of the will upon the body, though not wholly suspended, is certainly considerably weakened. In this sort of sleep it is still less suspended over the mind, for a man makes a bargain in his dreams, and examines the terms of the bargain, and dwells upon one part of it with some accuracy; he argues in his sleep, not merely repeating, as has been said, arguments which have occurred to him in his waking hours, but inventing new ones, with some pains and attention. I mention these |