CHAPTER IV 



MENTAL DEVELOPMENT IN THE INDIVIDUAL 



i . IN mental as in physical evolution, the emergence of new 

 factors does not involve the total disappearance of the old. 

 These are merely overlaid and in varying degree modified 

 by the later development. Just as man remains an animal, 

 so the most reflective consciousness coexists with the most 

 irrational impulse and the life of the most perfect and com- 

 plete human being has its roots in methods of action and 

 reaction which it shares not only with the life of the savage 

 or of the dog, but with that of the rhizopod or the plant. 

 Thus we get in the developed man a rough epitome of the 

 history of the race, we find in him modes of action which 

 represent all the stages which the race has passed through. 

 The correspondence is not indeed accurate, for the presence 

 of new factors modifies the operation of those which are 

 older, but (as in embryology) it is sufficiently near to 

 enable us to form a rough outline of the evolutionary pro- 

 cess, an outline which we can verify and correct by com- 

 parison with the actual behaviour of animals at different 

 grades of development. 



We may therefore suitably approach our task by dis- 

 tinguishing the elements discoverable in the activity of the 

 developed man, and considering their analogues in the 

 animal world. In doing so, since we conceive the organism 

 as a psycho-physical unity, we shall take physical reactions 

 into account along with the deliverances of consciousness, 

 using, in any case, the evidence most readily accessible and 

 most easily verifiable. 



Having taken correlation to be the typical function of 



