Page:Popular Science Monthly Volume 13.djvu/187

Rh cutting loose from the rule of the senses, the making them servants instead of kings; the base-line the eye may trace out, but reason must construct the triangle; the arc and chord may be measured by the hand, but only calculation gives us the limits of the circle.

The deceptions of the senses are wellnigh as marked as their limitations; indeed, are a part of their limitations. Reid, the metaphysician, argues elaborately that the so-called deceptions of the senses are rather mistakes of judgment in regard to the impressions made on the nerves of special sense. Such argument is needless, since all the convictions that we acquire through the senses—the truths as well as errors—are the products of judgment. It is not the eye, but the brain behind the eye, that sees. The impressions made on the retina do not of themselves carry thoughts to the mind, any more than the impression on the photographer's plate carries thought to the instrument behind it. The eye is an instrument through which the brain sees—the telescope and microscope of the mind. Of itself the eye is as incompetent to see as is the telescope to discover a new planet, or the microscope to detect a humble organism.

"The eye sees what it brings the means of seeing; "it is the astronomer and microscopist that discover; it is the brain that sees through the doors opened by the eye. Conceptions and misconceptions, obtained through the sense of vision, are alike products of the brain rather than of the seeing apparatus. In scientific strictness our senses neither teach nor deceive us.

Although the eye is, as has been said, the best of the senses, it is yet, in some respects, the worst, as more untruths or half-truths enter the brain through this sense than through all the other senses combined; the very efficiency and value of the vision, its clearness and comprehensiveness, its apparent certainty and grasp of detail, cause us to repose in it with greater confidence, and to yield to its suggestions with fewer questionings. Forgetting the limitations of the optical apparatus, and assuming that its office is not to see but to provide the mechanism of seeing—quite overlooking the obvious facts that we never see the whole of objects but only their surfaces, usually but one or two sides at most; that it is practically impossible to fully fix the attention on two widely-separated objects simultaneously; that form and color and size, which are learned through sight, may be of far less importance in determining the nature of objects than their other qualities—men erroneously judge that what is seen is necessarily the truth and the whole truth. When I look at any object, as a chair, I do not see it, cannot see it, however near it may be, and however good my eyesight or concentrated my attention; I see only the bare surface of the portion that is turned toward me, which is but an infinitesimal fraction of the chair itself; and though I turn it round and round, and look at every side, I can never see it, while only a portion of its surface even can ever be seen at one time. Such is part of the philosophy of the