90 EVIDENCES AND LIMITATIONS 



causation fully to account for them. Accordingly they 

 acknowledge that physical evolution does not entirely 

 explain the origin of species, but merely describes their 

 physical antecedents and the physical conditions of 

 their origin. That unknown factors have part in species 

 forming is confessed, and the possibility that these 

 factors are partly at least superphysical may be, and 

 has been, conceded witliout doing violence to physical 

 science. 



It is not a postulate of physical science that such 

 science should be able to solve all problems raised by 

 scientific experience. Its theories are limited in appli- 

 cation, and leave many questions unanswered. Thus 

 the evolutionary theory postulates the existence of life, 

 and therefore cannot rightly be understood to be con- 

 cerned with the problem of its origin. That theory 

 simply describes the development of the physical 

 organisms in which life is found. This development 

 is attended by the appearance of certain specific 

 characters which purely physical antecedents and con- 

 ditions do not and cannot explain : — such, for instance 

 as instinct, reason, and moral sense. The inference to 

 be drawn from this is that these characters are not 

 wholly accounted for by natural evolution, but require 

 for their development what is called involution — that 

 is, the coming in of higher factors than can be regarded 

 as belonging to the purely physical order. 



No possible mechanical adjustment or rearrange- 

 ment of physical conditions can of itself produce a 

 superphysical effect. Such an effect requires super- 



