CHAPTER I 



THE NATURE AND SIGNIFICANCE OF 

 MENTAL EVOLUTION 



i . IN the biological theory of evolution the development of 

 mind takes a secondary place. The biologist is concerned 

 with the laws of variation and heredity. As an evolu- 

 tionist, his main interest lies in showing that certain known 

 facts of variation and certain established laws of heredity 

 suffice to explain the development of the existing forms 

 of flora and fauna in all their wealth from a single primitive 

 type. A parent organism, an original living being he has 

 for the present to assume. Recent physico-chemical re- 

 search has indeed strongly suggested that the evolutionary 

 principle extends beyond the living world, that the specific 

 forms or ' elements,' as we still call them, of c inanimate 

 matter ' may be conceived as developing in geologic time 

 from a simpler, perhaps from a single primoridial type, and 

 that this type would be something (if the expression be 

 allowed) not strictly material, but rather pre-material. But 

 the gulf between the living and the inanimate remains for 

 the present un-spanned. The biologist has to assume the 

 existence of living tissue, just as the physicist has to take 

 the existence of negative and positive electrons as a datum 

 which he does not seek to explain. Granted the existence 

 of the living germ, however, the biologist can do much 

 towards explaining the derivation from this single source 

 of the vast complexity of forms which actually people the 

 world. Not that in c explaining ' he pretends to give the 

 ultimate reason for all that he finds. Ultimate reasons are 

 not precisely the concern of a special science. He explains 



