This theory is now
commonly known by the name of Naturalism; according to it the facts
dealt with by the natural sciences are the only reality which is
knowable; man's nature is part of these and has to be adapted to
them, and there is nothing further with which it can be brought into
relation. This theory is not the same as the scientific theory of
evolution, nor is it a necessary consequence of it; but in the
minds of many the two go together. The conclusion of the preceding
argument--that the ethical significance of evolution is not deep
enough to give any answer to the fundamental question of morals--is
not a criticism of the theory of evolution so far as restricted to
the domain of science, but it is a criticism of the Naturalism which
professes to be a final philosophy.

III.

ETHICS AND IDEALISM.

There has been no movement of metaphysical thought in our time which
can be compared for its widespread influence or for its general
acceptance with the theory of evolution in biological science.
Intimate as is its connexion with the progress of science, metaphysics
does not keep step with it,--any more than it simply marks time as the
former advances. It reflects the influence of each new generalisation
of science; but if and so far as it reflects this influence only, it
cannot be an adequate metaphysics. Metaphysics must re-think each new
fact brought to light, each new generalisation established by science.
It must think them in their relation to the whole, and attempt to
understand them by setting them in their place in the complete system
of knowledge and reality. This complete system is indeed an
ideal, never adequately comprehended by the human mind; but it is
nevertheless the ideal which determines all efforts of constructive
philosophy--including those efforts which take the generalisation of
some special science as their all-comprehending principle. An attempt
of this kind to make a philosophy out of a scientific generalisation
has in our own time been the obvious result of the theory of
evolution, and has given new vogue to the philosophical system called
Naturalism. That system draws its strength from the scientific
doctrine of evolution; but as a philosophy it gives an extended
application to the generalisation established by a group of sciences,
and valid for the facts within their range. It interprets the law
of development which rules the sequences of nature as the highest
attainable princi