XXXI.] MENTAL HABIT. "53 



habits are liable to be lost by disuse. This is universally 

 true, and it is perhaps more conspicuously true of mental 

 habits than of any other kind. Memory, as we have seen, 

 is altogether due to mental habit, or association, and con- 

 sists in the liability of associations to be recalled into 

 consciousness. In virtue of the law of the loss of habits Forget- 

 by disuse, any association which remains for a sufficiently ^ °]^'gg ^f^® 

 long time without being recalled into consciousness, ulti- habits by 

 mately loses the power of being so recalled ; in common 

 language, it is forgotten. But we have also seen that the Reappear- 

 tenacity of a habit does not always depend on its promi- ^^^^ °i 

 nence, or present strength ; and that a tenacious habit may supposed 

 revive after appearing to be lost. To this class of facts *° ^^ ^°®*' 

 belongs the very remarkable yet not uncommon fact of 

 the recollection in illness or in delirium, of long-forgotten 

 memories of childhood. 



r 



As the law of habit is a law of all life, so the law of Associa- 

 mental habit, or the law of association, is a law of all J^™ ^ J^""^ 

 mind. It enters into aU mental processes. Memory, as mental 

 we have seen, consists in the power of recalling associations !! ^' 

 that have been once formed. The acquisition of knowledge Accuisi^' 

 consists in the formation of associations : the learnincf of a tion of 

 language, for instance, consists in the formation of associa- ledgl' 

 tions between the words and their meanings, so that either 

 will recall the other. The acquisition of knowledge con- 

 cerning things consists in the formation of associations 

 between the various properties of the things, and the 

 acquisition of the power of recalling those associations to 

 memory when they are wanted. Accuracy of knowledge Accurate 

 consists in the associations which are formed in the mind f^^^' 

 between things, and between their properties, accurately 

 corresponding to the combinations that exist in the real 

 world. Errors of knowledge consist in failures in the Error. 

 correspondence. Reverie chiefly consists in associations Kcverie. 

 successively recalling each other to memory without any 

 effort of will. Imagination, or invention, consists in the Invention, 

 formation within the mind of ideal associations, which the 

 inventor may afterwards construct as actual combinations 



