THEORIES OF EVOLUTION 109 



facts in evolution, the situation becomes one of 

 scant hope. 



It is necessary at the outset for every evolutionist 

 to establish his articles of faith if he would be 

 understood, for this, in the end, is the basis for 

 our investigations until our knowledge can be 

 brought to greater exactness. It must be admitted 

 that no one view has been established to the exclu- 

 sion of all others by scientific proof, hence these 

 articles of faith should be at once a basis for study 

 and a confession of the tentative nature of all 

 evolutionary theories. The attitude of every indi- 

 vidual must be based in some degree on what he 

 finds it possible to believe, and belief is not final 

 proof. With such an attitude toward his subject, 

 the evolutionist may examine the work of his fel- 

 lows fairly, and without bias accept such modi- 

 fying factors as may be brought to bear upon his 

 own views. If anything is necessary to progress in 

 our knowledge of the processes of evolution it is 

 this very recognition of limitations : limitations of 

 knowledge and of the interpretation of facts, limi- 

 tations of the other fellow's work and of one's own. 



The spirit of fairness demands that we consider 

 the beliefs of the vitalists as well as those of the 

 mechanists, if only to make clear our reasons for 

 abandoning the vitalistic approach. We have no 

 more evidence for the non-existence of a vitalistic 

 principle than for its existence. Nevertheless a 



