SCIENTIFIC STUDY OF HUMAN TESTIMONY. 175 



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 limi- 

 tations ; indeed, are a part of their limitations. Reid, the metaphysi- 

 cian, 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 con- 

 victions 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 impres- 

 sion on the photographer's plate carries thought to the instrument be- 

 hind it. The eye is an instrument through which the brain sees the 

 telescope and microscope of the mind. Of itself the eye is as incompe- 

 tent to see as is the telescope to discover a new planet, or the micro- 

 scope to detect a humble organism. 



" The eye sees what it brings the means of seeing ; " it is the astron- 

 omer and microscopist that discover ; it is the brain that sees through 

 the doors opened by the eye. Conceptions and misconceptions, ob- 

 tained 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 en- 

 ter the brain through this sense than through all the other senses com- 

 bined ; 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 quali- 

 ties 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 frac- 

 tion 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 



