CHAP. XXXI.] MENTAL HABIT. 49 



The law of the association of ideas is generally mentioned 



as if it were an ultimate law. Now, it is no doubt an 



ultimate law, so far as psychology only is concerned. It 



is true of all mental phenomena, and it is not resolvable 



into any other mental law. But the phenomena of mind 



are only a part of the phenomena of life, and the law of 



the association of ideas is only a particular case, though a 



very important one, of a law which is true of all the 



phenomena of life — namely, the law of habit. In order to 



keep this truth before the reader's mind, I intend to speak 



of mental habit in preference to the association of ideas, 



though I admit that the association of ideas is a perfectly 



accurate expression, and I shall use it wherever it will 



best serve to express my meaning. 



Ideas may be defined as all those impressions on con- impres- 



sciousness and thought which are not due to immediate ^^°"^ P'^ 



o conscious- 



impressions of sense. All impressions on the mind, con- ness are 



sequently, which are not sensory are ideal. This use of sensory or 

 the word idea is perhaps rather wider than is sanctioned ^'^^'^l- 

 by common usage, but it is intelligible and, I think, 

 necessary for the purposes of science. 



The elementary law of association may be thus stated : — Law of as- 

 When two feelings have been experienced together, or in stated ""^ 

 immediate succession, the recurrence of either of the feel- 

 ings separately tends to recall to memory the conscious- 

 ness of the other feeling ; or, in fewer words and less 

 technical language, feelings that have been experienced 

 together tend to recall each other. Let us call two sensa- 

 tions, or groups of sensations, A and B ; and let us caU the 

 consciousness of the two respectively a and h. If A and B 

 have often occurred togetlaer, or in immediate succession, 

 a and h also will have occurred together, or in immediate 

 succession ; and, in virtue of the law that all the actions of 

 living beings tend to become habitual, a and b will acquire 

 the habit of occurring together, and whatever produces the 

 one will recall the other also. Or, to use an illustration 

 instead of an algebraic statement : the sight of a man's instance 



o <J J? » 



face and the sound of his voice may become so associated '^^^^ ^^^ ^ 

 together in the mind, that the consciousness, or memory, of Ws voice. 



VOL. IL E 



