yed; while the facts of beauty were taken as
constituting no less conclusive evidence of the quality of such special
design as beneficent, not to say artistic. But now that the Darwinian
doctrine appears to have explained scientifically the former class of
facts by its theory of natural selection, and the latter class of facts
by its theory of sexual selection, we may fitly conclude this brief
exposition of the doctrine as a whole by considering what influence such
naturalistic explanations may fairly be taken to exercise upon the
older, or super-naturalistic, interpretations.

To begin with the facts of adaptation, we must first of all observe that
the Darwinian doctrine is immediately concerned with these facts only in
so far as they occur in organic nature. With the adaptations--if they
can properly be so called--which occur in all the rest of nature, and
which go to constitute the Cosmos as a whole so wondrous a spectacle of
universal law and perfect order, this doctrine is but indirectly
concerned. Nevertheless, it is of course fundamentally concerned with
them to the extent that it seeks to bring the phenomena of organic
nature into line with those of inorganic; and therefore to show that
whatever view we may severally take as to the kind of causation which is
energizing in the latter we must now extend to the former. This is
usually expressed by saying that the theory of evolution by natural
selection is a mechanical theory. It endeavours to comprise all the
facts of adaptation in organic nature under the same category of
explanation as those which occur in inorganic nature--that is to say,
under the category of physical, or ascertainable, causation. Indeed,
unless the theory has succeeded in doing this, it has not succeeded in
doing anything--beyond making a great noise in the world. If Mr. Darwin
has not discovered a new mechanical cause in the selection principle,
his labour has been worse than in vain.

Now, without unduly repeating what has already been said in Chapter
VIII, I may remark that, whatever we may each think of the measure of
success which has thus far attended the theory of natural selection in
explaining the facts of adaptation, we ought all to agree that,
considered as a matter of general reasoning, the theory does certainly
refer to a _vera causa_ of a strictly physical kind; and, therefore,
that no exception can be taken to the theory in this respect on grounds
of _logic_. If the theory in