112 THE PROBLEMS OF EVOLUTION 



up as a mechanist, to be sure, but to the extent 

 that he is a true scientist it will make no difference 

 to him whether they prove the mechanistic or the 

 vitalistic concept, provided only that they ulti- 

 mately result in proof. 



The foundations of mechanistic theories of evo- 

 lution are in one way only a step removed from 

 the vitalistic. They have the marked advantage 

 of limiting themselves to primary concepts which 

 are at least susceptible to scientific proof, while the 

 ideas of vitalism are beyond the reach of existing 

 scientific methods, but their susceptibility has not 

 yet come to fruition. The obstacles to scientific 

 treatment of the materials of evolution are so 

 great that our understanding and acceptance of 

 them still rest on logical appeal rather than on 

 scientific values, hence the basis of faith with 

 which they are inevitably associated. It is often 

 difficult in this field to say with certainty when an 

 observation is factual and when it is limited by 

 incompleteness of data and by the personal equa- 

 tion. But we are human, and the best that we can 

 do is to admit the probable accuracy of observa- 

 tions checked and rechecked, and agreed upon by 

 many scientists rather than by one or two individ- 

 uals. Pioneer efforts cannot partake of this sup- 

 port, but they should at least be amenable to it. 



Accepting only the well-established theories of 

 evolutionary method our remaining articles of 



