Mental Evolution. 503 



removed from life-preserving activities, is determined 

 mainly by the law of congruity. But there are several 

 such systems. There are, indeed, as many systems as 

 there are minds ; but these may be classified in several 

 distinct groups, which we may liken to genera and species. 

 These are the various interpretations of nature, theories of 

 things, and the like ; the systems of ideas, thoughts, con- 

 ceptions, emotions, beliefs, which, as we say, belong to us, 

 each and all, and which determine to which metakinetic 

 species we belong. These are the highest products of 

 mental evolution ; and among them there is, so to speak, 

 a struggle, if not for existence, at any rate for prevalence. 

 Which shall eventually prevail -a spiritual interpretation of 

 nature, a material interpretation, a monistic interpretation, 

 or other, who shall say ? But, so far as we can judge, the 

 winning species among systems of ideas and interpreta- 

 tions of nature are likely to be those in which the greatest 

 number of ideas are fused into harmonious synthesis ; in 

 which all the ideas are congruous ; and in which the 

 abstract or conceptual ideas, when brought into contact 

 with concrete or perceptual states of consciousness, are 

 found to be in harmony and congruity therewith. 



