DISCRIMINATION AND COMPARISON. 515 



an ' overtone ' helps us to detect tlie latter in a comjDound 

 sound {supra, pp. 439-40). A dim doubleness grows clearer 

 by being assimilated to the image of a distincter doubleness 

 felt a moment before. It is interpreted by means of the 

 latter. And so is any difference, like any other sort of im- 

 pression, more easily perceived when w^e carry in our mind 

 to meet it a distinct image of what sort of a thing we are to 

 look for, of what its nature is likely to be.* 



These tivo processes, the reinforcement of the terms by 

 disparate associates, and the filling of the memory with 

 past differences, of similar direction with the present one, 

 but of more conspicuous amount, are the only explanations 

 lean offer of the effects of education in this line. What is 

 accomplished by both processes is essentially the same 

 thing : they make small differences affect us as if they were 

 large ones — that large differences should affect us as they do 

 remains an inexplicable fact. In principle these two pro- 

 cesses ought to be sufficient to account for all possible 

 cases. Whether in fact they are sufficient, whether there 

 be no residual factor which we have failed to detect and 

 analyze out, I will not presume to decide. 



PRACTICAL INTERESTS LIMIT DISCRIMINATION. 



It will be remembered that on page 509 personal inter- 

 est was named as a sharpener of discrimination alongside 

 of practice. But personal interest probably acts through 

 attention and not in any immediate or specific way. A 

 distinction in which we have a practical stake is one which 

 we concentrate our minds upon and which we are on the 

 look-out for. We draw it frequently, and we get all the 

 benefits of so doing, benefits which have just been ex- 

 plained. Where, on the other hand, a distinction has no 

 practical interest, where we gain nothing by analyzing a 

 feature from out of the compound total of which it forms a 



* Professor Llpps accounts for the tactile discrimination of the blind 

 in a way which (divested of its ' mythological ' assumptions) seems to me 

 essentially to agree with this. Stronger ideas are supposed to raise weaker 

 ones over the threshold of consciousness by fusing with them, the tenden- 

 cy to fuse being proportional to the similarity of the ideas. Cf. Grundtat- 

 sachen, etc., pp. 233-3 ; also pp. 118, 492, 526-7. 



