AFTERWORD 



With the close of the nineteenth century the hour hand of 

 biological science had completed another revolution. One 

 after another, the classic systems of evolution had passed into 

 the discard, as its remorseless progress registered their doom. 

 The last of these systems, De-Vriesianism, enjoyed a meteoric 

 vogue in the first years of the present century, but it, too, has 

 gone into eclipse with the rise of rediscovered Mendelism. 

 Notwithstanding all these reverses, however, the evolutionary 

 theory still continues to number a host of steadfast adherents. 



Some of its partisans uphold it upon antiquated grounds. 

 Culturally speaking, such men still live in the days of Darwin, 

 and fail to realize that much water has passed under the 

 bridge since then. It has other protagonists, however, who are 

 thoroughly conversant with modem data, and fully aware, 

 in consequence, of the inadequacy of all existent formulations 

 of the evolutional hypothesis. Minds of the latter type are 

 proof, apparently, against any sort of disillusionment, and it 

 is manifest that their attitude is determined by some con- 

 sideration other than the actual results of research. 



This other consideration is monistic metaphysics. In defect 

 of factual confirmation, evolution is demonstrated aprioristi- 

 cally from the principle of the minimum. The scope of this 

 methodological principle is to simplify or unify causation by 

 dispensing with all that is superfluous in the way of explana- 

 tion. In olden days, it went by the name of Occam's Razor 

 and was worded thus: Entia non sunt multiplicanda praeter 

 necessitatem — "Things are not to be multiplied without neces- 

 sity." Evolution meets the requirements of this principle. It 

 simplifies the problem of organic origins by reducing the num- 

 ber of ancestors to a minimum. Therefore, argues the evolu- 

 tionist, evolution must be true. 



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