THE DEVELOPING CONCEPT AND ITS FUNCTIONS 199 



relationships. Yet the distinction does not fade away entirely. 

 In such a concept as evolution, for example, it comes out very 

 clearly. On the side of content, evolution means a process of 

 change distinguished by certain definite characteristics; on the 

 side of import, it means no less than a whole new principle of 

 classification, almost one might claim, of scientific procedure. 

 Moreover, what we found to be true of the formation of the 

 simpler general concepts seems to hold equally of these more 

 complex and abstract ones namely, that the association of the 

 ideas composing a concept rests primarily upon the common 

 functional significance of the objects denoted by the concept in 

 question. This may perhaps be illustrated by the transforma- 

 tion wrought in the traditional biological classifications by the 

 concept of evolution. The most advantageous principle for the 

 classification of organic groups has come to be descent from a 

 common parent stock. That is to say, common descent is the 

 characteristic which calls for similar intellectual treatment of 

 the organisms possessing it. The concept of the species thus 

 determined accordingly comes to include as essential characteris- 

 tics other common features of the organisms which it is scarcely 

 conceivable would have been selected and associated for any 

 other reason. Identity of import thus conditions the association 

 of related similarities, which so become content. The basis for 

 no scientific classification is mere unmotived association of like- 

 nesses, however striking in themselves. 



Secondly, in the later development of general concepts, there 

 is observable the appearance of a tendency which marks the 

 development of all organic structures, namely, the tendency 

 toward fixity and loss of plasticity. In the case of the concept 

 this increase in fixity seems to be reinforced by the necessity of 

 counteracting the unwieldiness of the more general concepts, 

 arising from the great complexity of their organization. The 

 fact that the development of these more complex organizations 

 depends upon their mutual dependence and relationship within a 



