CH. xvn METAPHYSICS OF NATURAL SELECTION 181 



we accept natural selection by struggle as a (or the) 

 great method of evolution and lever of progress in 

 nature ? There is no great presumption, surely, in 

 putting the question ! The evidence in favour, not of 

 organic evolution, but of natural selection as its 

 method, is deductive and hypothetical ; the same thing 

 indeed is true of many of our scientific theories. The 

 evidence for natural selection is as follows : (1) Struggle 

 and selection are facts ; (2) They will given time 

 enough account for quite as much progress, quite as 

 much differentiation as we see in the cosmos of life ; 

 (3) Therefore, by the law of parsimony, they have 

 caused it. All this is only probable evidence, and " the 

 plurality of causes" may undermine it. Accordingly 

 we claim the right of criticising the theory, and of asking 

 whether it is antecedently credible. Is it thinkable that 

 the evolution of life proceeds along lines of struggle ? 

 Surely that is thinkable. The doctrine merely implies 

 that living organisms are parts of nature and are treated 

 as such ; that though the organic and the animal may 

 approach the spiritual, they have not yet reached it. 

 And, by naming one intelligible and thinkable process 

 of evolution in organisms, Darwin has even helped the 

 cause of sound philosophy and the cause of faith. 

 When we meet with intelligible processes, we perceive 

 the presence of reason in the world ; and when the 

 Christian perceives reason at work, he is more than ever 

 assured that the world he lives in is God's world. 



Force and Force. Symmetry with what has gone 

 before would lead us to head our next paragraph with 

 these words. But it is questionable whether we can 

 fairly charge Darwin with treating the different biological 

 forces involved in natural selection life, variability, 

 heredity as mutually independent and merely coin- 



