SELF 233 



in the absence of which, there is no phenomenon. The 

 new psychology is physiological. The old was meta- 

 physical. Note the material elements of a Spencerian 

 definition of an idea. "The psychical side of what, 

 on its physical side, is an involved set of molecular 

 changes, propagated through an involved set of nervous 

 plexuses; that which makes possible the idea is, the 

 pre-existence of these plexuses, ' ' and they are the only 

 part of the phenomenon that persists. The assumption, 

 that there is any other element, takes the statement of 

 it out of the realm of psychology, or science, into that 

 of metaphysics. Spencer's definition of an idea is in- 

 ductive, or scientific. Note the contrast between that 

 and Descartes' definition, in which the physiological 

 element is omitted. Descartes says: "By the word 

 idea, I understand that form of thought, by the imme- 

 diate perception of which I am conscious of some 

 thought." No scientific definition can be given, except 

 that the physiological changes, constituting the phe- 

 nomenon, give the psychical effect. Descartes meant 

 that self-consciousness the perception of the thoiight 

 is the distinction between man, who has a "soul," 

 and an animal who does not perceive his thoughts and 

 has no "soul." But why should an idea, or its defini- 

 tion, be confined to this narrow conception? An idea 

 is the conclusion of thought, a conception of what is 

 best, or ought to be, an opinion. 



The reason why the physiological, or material defini- 

 tion of thought is more comprehensive, is that it em- 

 braces the idea of the close connection between all 

 thought and life preservation. Whatever appeals to 

 man's physical nature, and preservation, is better un- 

 derstood, than an abstract idea dissociated from any 

 physical connection. 



