2 MENTAL EVOLUTION IN MAN. 



I think that any such endeavour — even were I qualified to 

 make it — would tend only to obscure my exposition of those 

 principles themselves. It is enough that I should trace the 

 operation of such principles, as it were, in outline, and leave 

 to the professed historian the task of applying them in special 

 cases. 



The present work being thus a treatise on human psycho- 

 logy in relation to the theory of descent, the first question 

 which it must seek to attack is clearly that as to the evidence 

 of the mind of man having been derived from mind as we 

 meet with it in the lower animals. And here, I think, it is 

 not too much to say that we approach a problem which is not 

 merely the most interesting of those that have fallen within 

 the scope of my own works ; but perhaps the most interesting 

 that has ever been submitted to the contemplation of our 

 race. If it is true that " the proper study of mankind is 

 man," assuredly the study of nature has never before reached 

 a territory of thought so important in all its aspects as that 

 which in our own generation it is for the first time approach- 

 ing. After centuries of intellectual conquest in all regions of 

 the phenomenal universe, man has at last begun to find that 

 he may apply in a new and most unexpected manner the 

 adage of antiquity — Know thyself. For he has begun to per- 

 ceive a strong probability, if not an actual certainty, that his 

 own living nature is identical in kind with the nature of all 

 other life, and that even the most amazing side of this his own 

 nature — nay, the most amazing of all things within the reach of 

 his knowledge — the human mind itself, is but the topmost 

 inflorescence of one mighty growth, whose roots and stem and 

 many branches are sunk in the abyss of planetary time. 

 Therefore, with Professor Huxley we may say : — " The impor- 

 tance of such an inquiry is indeed intuitively manifest. 

 Brought face to face with these blurred copies of himself, the 

 least thoughtful of men is conscious of a certain shock, due 

 perhaps not so much to disgust at the aspect of what looks 

 like an insulting caricature, as to the awaking of a sudden 

 and profound mistrust of time-honoured theories and strongly 



