THE PSYCHOLOGY OF PREJUDICE. 637 



ing that to a considerable extent we have selected our own ex- 

 perience. 



Our second law affirms that we see the world not as it is but 

 as modified by the individual peculiarities of our minds. The 

 illusions that result are Bacon's well-known " idols of the den," 

 doubtless the most fruitful of the four sources of error pointed 

 out by that clear-headed philosopher. For our starting-point we 

 may turn again to physics and physiology. Vibrations of the 

 luminiferous ether of varying rapidity are perceived by the eye 

 as a harmony of colors. Vibrations of the air of varying rapidity 

 are perceived by the ear as a harmony of tones. Unless, now, 

 we are prepared to say that the colors red or green, or that the 

 tones a or a', are like or in any way similar to the motion of the 

 ether or air ; unless, further, we are prepared to say that, corre- 

 sponding to the subjective harmony of colors and tones which we 

 feel, there is an objective harmony of motions in the ponderable 

 stuff, then we must admit that we have here cases of the great 

 primary illusion of a phenomenal world of ideas like a noumenal 

 world of things-in-themselves. With this ancient problem of per- 

 ception we are not now concerned, but it serves as an illustration 

 of our mental law of apperception. As the eye and the ear, each 

 according to its structure, make over the manifold motions of the 

 external world into sensations of light and sound, so the mind 

 makes over the materials of knowledge into this or that product 

 according to its peculiar constitution. Observe, however, this 

 difference between the two cases. While the eye and the ear vary 

 little in structure in different individuals, the variations in mental 

 structure are endless, being determined by our environment, edu- 

 cation, and inherited peculiarities. Color-blindness is compara- 

 tively rare and limited to a few colors ; psychical blindness, in a 

 greater or less degree, is a defect no man is free from. 



The simpler illustrations of this law need not detain us. We 

 put any new phenomenon into that class of our previous notions 

 which it most closely resembles. A child who sees a cow for the 

 first time calls it a horse, if familiar with horses. The same plant 

 may be apperceived by a girl as a flower, by a farmer as a weed, 

 by an old woman as an herb. The story of the precocious boy is 

 in point. He sat under a tree as three strangers passed by. The 

 first said, " What a fine stick of timber ! " " Good-morning, car- 

 penter," said the boy. The second, " What excellent bark ! " 

 "Good-morning, tanner." The third, "What a beautiful tree- 

 top ! " " Good-morning, artist." He had correctly interpreted 

 their vocations from their manner of apperceiving the tree. Our 

 habits of thought, once started, grow on any food. We go by 

 chance to hear a lecturer of an opposite party or sect, and come 

 away confirmed in our own views. This law of mental inertia 



