XX Journal of Comparative Neurology. 



which is eftected the physical elimination, by death or failure to procreate 

 their kind, of those who fall below mediocrity ; selective mating is the 

 giving expression to certain preferences or ideals. By natural selection 

 all are plucked in life's examination who do not reach a certain standard 

 of excellence : by selective mating particular individuals are picked out 

 by an act of selective choice. Natural selection has guided the mental 

 symbolism to certain developments by eliminating those in whom these 

 develop nents were absent : selective mating is a product of the menta 1 

 symbolism so developed. It is itself the outcome of psychogenesis. And 

 however important it may be as a factor in social development it is rather 

 the result of than the cause of the higher phases of mental evolution. 



The Law of Truth. In seeking an answer to the question : What is 

 the law of psychogenesis? it will be well to start from the higher and 

 more abstract region of concepts and work our way downwards to the 

 more practical level of percepts; and then, having found certain subsidiary 

 laws or principles, to see if there does not run through these a single basal 

 law or principle. 



What is the guiding principle of development in intellectual matters? 

 I would call it the law of truth. In the course of my reading and of my 

 converse with my fellow-men I find the facts of nature and of human con- 

 duct and experience interpreted in a number of difTerent ways. Some of 

 these interpretations I unhesitatingly accept as true ; others with as little 

 hesitation I reject as false ; many I ignore or relegate to a suspense account. 

 On what ground do I at once accept certain interpretations and reject 

 certain others? It is often difhcult to give, off-hand, the specific grounds 

 of acceptance or rejection. But it practically comes to this. I accept 

 what is in accordance with my own views and theories : I reject what is 

 contrary to my own scheme. I relegate to a suspense account, or ignore, 

 what neither accords fully with my system of interpretation of nature, of 

 life and of man, nor actually conflicts with the interpretation. I neither 

 accept nor reject what seems to be irrelevant. . . . The true is 

 accepted, the false rejected ; the rest more or less ignored No man 

 consciously accepts the false, or rejects the true. ... To say that 

 any one believes what he deems untrue is a contradiction in terms. 



The Law of Psychogenesis. Enough has now been said to indicate 

 what I regard as the law of psychogenesis. As in the case of natural 

 selection, propjrly understood, it is a law ef elimination — the elimination 

 of the incongruous. It applies not only to the relations of concepts inter se ^ 



