Lectures on the Philosophy of the Human Mind (Vol. 1 of 3)

by Thomas Brown

I have said, that the knowledge of the real magnitude, figure, and position of bodies, could not be obtained immediately from the diversities of the mere surfaces of light at the retina; unless it were the suggestion of some instinctive principle, by which the one feeling was, originally and inseparably, connected with the other: and I have made this exception, to prevent you from being misled, by the works on this subject, so as to think, that the original perception of distance implies, in the very notion of it, a physical impossibility. Some diversity there evidently must be of the immediate sensation of sight, or of other feelings coexisting with it, when a difference of magnitude or figure is suggested: the visual affection, which is followed by the notion of a mile, cannot be the same as that which is attended with the notion of half a foot; nor that which is attended with the perception of a sphere, be the same as that which suggests a plane circular surface. Whatever the number of the varied suggestions of this kind may be, there must be, at least, an equal variety of the immediate sensations that give rise to them; and these corresponding series of sensations and suggestions, may originally be associated together by an instinctive principle, as much as any other pairs of phenomena, the connexion of which we ascribe to instinct; or, in other words, suppose an adaptation of them to each other, by the gracious provision of the Power which formed us, for a purpose unforeseen by us, and unwilled at the moment. It is not more wonderful, a priori, that a sensation of colour should be immediately followed by the notion of a mile of distance, than that the irritation of the nostril, by any very stimulant odour, should be immediately and involuntarily, followed by the sudden contraction of a distant muscular organ, like the diaphragm, which produces, in sneezing, the violent expiration necessary for expelling the acrid matter;—or that an increase of the quantity of light poured on the eye, should be instantly, and without our consciousness, followed by a contraction of the transparent aperture. I am far from saying, that there truly is such an instinctive association of our original visual feelings, with corresponding notions of distance and magnitude, in the present case; for, at least in man, I believe the contrary. I mean only, that the question has, a priori, only greater probability on one side, not absolute certainty; and that experience is necessary, before we can decide it with perfect confidence.

In the case of the other animals, there seems to be little reason to doubt, that the tedious process, by which man may be truly said to learn to see, is not necessary for their visual perceptions. The calf, and the lamb, newly dropt into the world, seem to measure forms and distances with their eyes, as distinctly, or at least almost as distinctly, as the human reasoner measures them, after all the acquisitions of his long and helpless infancy. Of these races of our fellow animals, Nature is as once the Teacher and the great Protectress,—supplying to them, immediately, the powers which are necessary for their preservation,—as, in the long continued affection of the human parent, she far more than compensates to man, the early instincts which she has denied to him. If the other animals had to learn to see, in the same manner with ourselves, it would be scarcely possible, that their existence should be preserved to the period, at which the acquisitions necessary for accurate perception could be made; even though the hoof had been an instrument of touch and measurement, as convenient as the hand. For this difference in the relative circumstances of their situation, the Almighty Being,—to whose universal benevolence, nothing which he has created is too humble for his care,—has made sufficient provision, in giving them that early maturity, which makes them, for many months, the superiors of him, who is afterwards to rule them with a sway, that is scarcely conscious of effort.

“Hale are their young, from human frailties freed,

Walk unsustained, and, unsupported, feed.

They live at once,—forsake the dam's warm side,—

Take the wide world, with nature for their guide,—

Bound o'er the lawn, or seek the distant glade,

And find a home in each delightful shade.”[121]

This instinctive suggestion, which, however subsequent it may be to the primary visual sensation, seems like immediate perception in the young of other races of animals, is a very strong additional proof, if any such were necessary, that there is no physical impossibility, in the supposition that a similar original suggestion may take place in man. The question, as I before said, becomes truly a question of observation and experiment.