XXXI.] MENTAL HABIT. 61 



were differeut ; and consequently the impressions produced 

 on my consciousness by the two incidents are compound 

 impressions, partly similar and partly different. But when 

 the second impression on my consciousness is made by 

 seeing the book for the second time, the idea of the book 

 is already habitually associated with the idea of the 

 bookseller's shop, and recalls it. 



This is what takes place in all cases of remembrance 

 by similarity. ISTo two incidents are similar in all their 

 details ; and when they are said to be precisely similar, it 

 is only meant that, of the compound impressions which all 

 incidents make on the consciousness, the parts that attract 

 the attention are the similar parts. When one thing, or 

 one incident, recalls another by its similarity, the one, 

 when compared with the other, may always be resolved 

 into a similar part and a dissimilar part. Let us call the 

 similar parts of two things, or of two incidents. A, and the 

 dissimilar parts X and Y ; the things themselves wiU con- 

 sequently be respectively indicated hy A X and A T. In 

 the act by which the mind has acquired its memory of 

 A X, A has already become associated with X as a case 

 of association by contiguity. So that when we say the 

 impression of A X on the consciousness recalls that of 

 A Y, what really happens is, that the impression of A, 

 which is the element common to the two, recalls that of Y. it is a case 

 Thus, association by resemblance is really a case of asso- tk,nT°^^' 

 elation by contiguity. contiguity. 



In order to prevent my meaning from being miscon- The power 



ceived, I ought to add that I regard the power of cosnisine °.^ °°^'" 



c X- o o smg re- 



resemblance and difference — in a word, the power of com- semblance 



parison— as an ultimate and original power of the mind, en?ets an 



not dependent on habit, association, or memory. I have ultimate 



indicated this view in the last chapter. It is, for instance, 



conceivable that the mind should compare two sensations, 



such as two spots of colour, simultaneously present to the 



consciousness, without any element derived from habit 



entering into the process. 



Most readers who will take the trouble to follow my 



reasonings on the subject of association by contiguity and 



E 2 



