I.H. XVI.] TSE EVOLUTION OF MIND. 147 



like tlie human bTain, we may expect to find a countless 

 number of transit-lines, of all degrees of permeability. 

 Those which have been oftenest traversed will be the most 

 permeable, and those which are traversed only at rare 

 intervals will be but slightly permeable ; while the passage 

 of a nervous discharge in a new direction will involve the 

 differentiation of a new line oi" transit. 



I^ow subjective psychology furnish(is us with an exact 

 parallel to this state of things. The profound analysis of 

 conscious changes carried on by the English school of psy- 

 chology since the time of Hobbes, and accepted by the 

 Kantian school in all save a few very important instances 

 — which we shall presently see to be similarly explicable — 

 has ended in the conclusion that states of consciousness 

 cohere with a strength dependent upon the frequency with 

 Ti'hich they have been repeated in experience. In other 

 words, " the persistence of the connection between states of 

 consciousness is proportionate to the persistence of the con- 

 nection between the agencies to which they answer. This 

 fundamental law of association is illustrated by such familiar 

 truths as the following : — " that phenomena wholly unrelated 

 in our experience, '-ve have no tendency to think of together; 

 that where a certain phenomenon has occurred in many rela- 

 tions, we usually imagine it as recurring in the relation in 

 which it has most frequently occurred ; that when we have 

 witnessed many recurrences of a certain relation we come to 

 have a strong belief in that relation ; that if a relation has 

 been daily experienced throughout life with scarcely an 

 exception, it becomes difficult for us to conceive it as other- 

 wise — to break the connection between the states of con- 

 sciousnes/j representing it; and that where a relation has 

 been perpetually repeated in our experience with absolute 

 uniformity, we are entirely disabled from conceiving the 

 oegation of it," ^ 



* Spencer, Princijiles of Psycholo ,ii. voL L p. 421 



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