THE EVOLUTION OF MIND 



of feeling of which thoughts and emotions are 

 made up. And if this be so, it becomes a mere 

 truism to say that the formation of a new asso- 

 ciation involves the establishment of a new 

 transit line, or set of transit lines, while the re- 

 vival of an old association involves merely the 

 recurrence of motion along old transit lines. 

 That this is merely a hypothesis, I readily 

 grant. Nevertheless it is a verifiable hypothesis ; 

 it is in harmony with all that we know of nerve 

 action ; and it may be held provisionally until 

 some better one is propounded. When we pro- 

 ceed to see how many phenomena it explains, 

 we shall be, I think, quite ready to admit that, 

 if it does not contain the whole truth, it must 

 at least contain a foreshadowing of the truth. 



For we have now to note that, by a deduc- 

 tion from an established law of molecular mo- 

 tion, this hypothetical law of nervous action can 

 be shown to explain that law of association 

 which subjective analysis proclaims as the fun- 

 damental law of intelligence. In the chapter 

 on Life and Mind, we saw that the chief busi- 

 ness of psychology is to answer the question 

 how there comes to be established in the mind 

 a relation between two subjective states x and y, 

 answering to a relation between two phenomena 

 A and B in the environment. How is it that 

 there is a subjective relation between the idea of 

 sweetness and the group of ideas comprised in 

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