The Origin of Sentient Life. 185 



and development, and it is proved incapable of setting 

 in a comprehensible order the most notable of the 

 phenomena. It is compelled to introduce an incom- 

 prehensible cause, not at one point only, but along 

 the entire stream of change. But to fall back on a 

 mysterious, inscrutable cause revealing itself in sen- 

 tient organic life at every instant and everywhere in 

 manifestations that co-operate with knowable causes, 

 and give to the result its special characteristics, is to 

 condemn evolution as a rational hypothesis. 



That this conclusion is just will appear the more 

 evident, if we consider the influence of feeling in the 

 growth and development of organisms. The loss of 

 nerve-sensibility is the precursor of decay in the 

 individual ; and the sense of pleasure and pain is, 

 perhaps, the most potent factor in the changes 

 wrought in living things in the course of generations. 

 Through pleasures and pains, the modifications which 

 arise are in great part effected. These feelings can- 

 not be either ignored or placed in a position so 

 relatively unimportant that they may be dealt with as 

 incidents, rather than causes in the process. Environ- 

 ing physical forces are, no doubt, continually operating, 

 and must produce their legitimate effect; but the 

 results brought about are not wholly due to forces 

 operating according to dynamic law ; they are in 

 great part owing to the activities called forth by the 

 sense of pleasure enjoyed in certain affections of the 

 organism, and the sen^e of pain suffered in others. 



