COSMIC PHILOSOPHY 



or ubiquitous alteration of animal and vegetal 

 forms, but includes, in a general way, all cases 

 of persistence of type, as well as all cases of 

 progress or retrogression. One and the same 

 general theory accounts for the fact that, while 

 some species thrive in the struggle for life and 

 acquire new capacities, others dwindle in num- 

 bers or deteriorate in structure, while others 

 'again maintain themselves unchanged through- 

 out immense periods. Throughout all these 

 cases, the general truth is easily discerned that 

 the total result will depend upon a very com- 

 plex combination of circumstances : the diffi- 

 culty is in applying the general truth to the 

 special cases that arise. Probably no naturalist 

 could point out all the specific circumstances 

 which have caused any one race of animals to 

 prevail over another in the struggle for life. 

 Such a task would probably demand a more vast 

 and minute knowledge of the details of the or- 

 ganic world than it is as yet possible for the most 

 unremitting industry, inspired by the highest 

 genius, to acquire. Yet no one doubts the gen- 

 eral principle that it is natural selection which 

 determines, not only which races shall prevail, 

 but also which races shall vary and which shall 

 remain unmodified. So in dealing with human 

 societies, in the primitive era with which the 

 present discussion is chiefly concerned, the his- 

 toric data are insufficient to enable us to ascer- 



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