The Evolution hypothesis 455 



in a variety of forms. It has made idealistic thinkers revise their 

 relation to the real world ; it has led positivistic thinkers to find a 

 closer connection between the facts on which they based their 

 views ; it has made us all open our eyes for new possibilities to arise 

 through the prima facie inexplicable "spontaneous" variations which 

 are the condition of all evolution. This last point is one of peculiar 

 interest. Deeper than speculative philosophy and mechanical science 

 saw in the days of their triumph, we catch sight of new streams, 

 whose sources and laws we have still to discover. Most sharply does 

 this appear in the theory of mutation, which is only a stronger 

 accentuation of a main point in Darwinism. It is interesting to 

 see that an analogous problem comes into the foreground in physics 

 through the discovery of radioactive phenomena, and in psychology 

 through the assumption of psychical new formations (as held by 

 Boutroux, William James and Bergson). From this side, Darwin's 

 ideas, as well as the analogous ideas in other domains, incite us to 

 renewed examination of our first principles, their rationality and 

 their value. On the other hand, his theory of the struggle for 

 existence challenges us to examine the conditions and discuss the 

 outlook as to the persistence of human life and society and of the 

 values that belong to them. It is not enough to hope (or fear?) 

 the rising of new forms ; we have also to investigate the possibility 

 of upholding the forms and ideals which have hitherto been the bases 

 of human life. Darwin has here given his age the most earnest and 

 most impressive lesson. This side of Darwin's theory is of peculiar 

 interest to some special philosophical problems to which I now pass. 



IV. 



Among philosophical problems the problem of knowledge has in 

 the last century occupied a foremost place. It is natural, then, to 

 ask how Darwin and the hypothesis whose most eminent repre- 

 sentative he is, stand to this problem. 



Darwin started an hypothesis. But every hypothesis is won by 

 inference from certain presuppositions, and every inference is based 

 on the general principles of human thought. The evolution hypo- 

 thesis presupposes, then, human thought and its principles. And 

 not only the abstract logical principles are thus presupposed. The 

 evolution hypothesis purports to be not only a formal arrangement of 

 phenomena, but to express also the law of a real process. It supposes, 

 then, that the real data — all that in our knowledge which we do not 

 produce ourselves, but which we in the main simply receive— are 

 subjected to laws which are at least analogous to the logical relations 



