COSMIC PHILOSOPHY 



not yet, indeed, estimate the age of the last great 

 glacial epoch with any approach to accuracy ; 

 yet the age which we assign to this epoch must 

 enter as an important factor into our estimates 

 of the antiquity of preceding epochs. But while 

 this point remains undetermined, it may be noted 

 that even the decision which leaves the smallest 

 time for the operation of unaided natural selec- 

 tion can weaken the Darwinian theory only on 

 the assumption that the agency already alleged 

 by that theory has been the sole factor concerned 

 in forwarding organic evolution — and this as- 

 sumption, though it may have been made by 

 over - confident disciples of Mr. Darwin, has 

 never been made by Mr. Darwin himself. Mr. 

 Darwin is too profoundly scientific in spirit to 

 imagine that, with all his unrivalled patience 

 and sagacity, he has completely solved one of 

 the most intricate problems with which the stu- 

 dent of nature has ever been called upon to deal. 

 It is more than likely that future research will 

 disclose other agencies which have cooperated 

 with natural selection in accelerating the diver- 

 sification of species. Meanwhile the evidence in 

 behalf of the first ten propositions involved in 

 the Darwinian theory is sufficiently strong to 

 make it apparent that a vast amount of specific 

 change must have taken place, and also that 

 natural selection has been a chief factor in pro- 

 ducing that change. To the arguments which 

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