THE COMPOSITION OF MIND 



ordinarily so called, is the classification of things. 

 When, for example, on perceiving two similar 

 triangles set side by side, we proceed to make 

 some inference from the known value of a side 

 in the one to the desired value of the correspond- 

 ing side in the other, the act is an act of reason- 

 ing. But when, on taking up two similar sea- 

 shells, we recognize them in their totality as 

 belonging to an oyster or some other familiar 

 mollusk, the act is an act of classification, com- 

 monly so called. In other words, if the per- 

 ception of similarity is followed by the thought 

 of one or more of the like relations which make 

 up similarity, we have an act of reasoning ; but 

 if it is followed by the thought of other objects 

 presenting like relations of similarity to the one 

 now perceived, we have an act of classification. 

 But closely related as these two mental op- 

 erations are now seen to be, we have not yet 

 disclosed the full extent to which they are re- 

 lated. Not only is classification involved in 

 every act of reasoning or inference, but reason- 

 ing or inference is involved in every act of 

 classification. Not only does reasoning consist 

 in the grouping of relations as like or unlike, 

 but the classification of things can go on only 

 through the grouping of relations as like or un- 

 like. To illustrate this, let us take a further 

 downward step, and consider a mental operation 

 apparently much simpler than those hitherto 



