Mental Evolution 425 



exercised a profound influence on this department of evolutionary 

 thought. And, for those who follow Darwin's lead, mental evolution 

 is still in a measure subservient to organic evolution. Mental pro- 

 cesses are the accompaniments or concomitants of the functional 

 activity of specially differentiated parts of the organism. They are 

 in some way dependent on physiological and physical conditions. 

 But though they are not physical in their nature, and though it is 

 difficult or impossible to conceive that they are physical in their 

 origin, they are, for Darwin and his followers, factors in the evolu- 

 tionary process in its physical or organic aspect. By the physiologist 

 within his special and well-defined universe of discourse they may be 

 properly regarded as epiphenomena ; but by the naturalist in his 

 more catholic survey of nature they cannot be so regarded, and were 

 not so regarded by Darwin. Intelligence has contributed to evolution 

 of which it is in a sense a product. 



The facts of observation or of inference which Darwin accepted 

 are these : Conscious experience accompanies some of the modes 

 of animal behaviour ; it is concomitant with certain physiological 

 processes ; these processes are the outcome of development in 

 the individual and evolution in the race ; the accompanying mental 

 processes undergo a like development. Into the subtle philosophical 

 questions which arise out of the naive acceptance of such a creed 

 it was not Darwin's province to enter ; " I have nothing to do," 

 he said 1 , "with the origin of the mental powers, any more than 

 I have with that of life itself." He dealt with the natural history 

 of organisms, including not only their structure but their modes of 

 behaviour ; with the natural history of the states of consciousness 

 which accompany some of their actions ; and with the relation of 

 behaviour to experience. We will endeavour to follow Darwin in 

 his modesty and candour in making no pretence to give ultimate 

 explanations. But we must note one of the implications of this self- 

 denying ordinance of science. Development and evolution imply 

 continuity. For Darwin and his followers the continuity is organic 

 through physical heredity. Apart from speculative hypothesis, 

 legitimate enough in its proper place but here out of court, we 

 know nothing of continuity of mental evolution as such : conscious- 

 ness appears afresh in each succeeding generation. Hence it is that 

 for those who follow Darwin's lead, mental evolution is and must 

 ever be, within his universe of discourse, subservient to organic 

 evolution. Only in so far as conscious experience, or its neural 

 correlate, effects some changes in organic structure can it influence 

 the course of heredity ; and conversely only in so far as changes 

 in organic structure are transmitted through heredity, is mental 



1 Origin of Species (6th edit.), p. 205. 



