Criticisms of Theory of Natural Selection. 377 
other hand, as we have seen in the preceding chapter, 
there is a vast accumulation of evidence in favour of 
the theory. Hence, it is no wonder that the theory 
has now been accepted by all naturalists, with scarcely 
any one notable exception, as at any rate the best 
working hypothesis which has ever been propounded 
whereby to explain the facts of organic evolution. 
Moreover, in the opinion of those most competent to 
judge, the theory is entitled to be regarded as some- 
thing very much more than a working hypothesis : 
it is held to be virtually a completed induction, or, 
in other words, the proved exhibition of a general 
law, whereby the causation of organic evolution ad- 
mits of being in large part—if not altogether— 
explained. 
-Now, whether or not we subscribe to this latter 
conclusion ought, I think, to depend upon what we 
mean by an explanation in the case which is before 
us. If we mean only that, given the large class of 
known facts and unknown causes which are conveni- 
ently summarized under the terms Heredity and 
Variability, then the further facts of Struggle and 
Survival serve, in some considerable degree or 
another, to account for the phenomena of adaptive 
evolution, I cannot see any room to question that 
the evidence is sufficient to prove the statement. 
But it is clear that by taking for granted thesc great 
facts of Heredity and Variability, we have assumed 
the larger part of the problem as a whole. Or, more 
correctly, by thus generalizing, in a merely verbal 
form, all the unknown causes which are concerned in 
these two great factors of the process in question, we 
are not so much as attempting to explain the pre- 
