ality and their value. On the other hand,
his theory of the struggle for existence challenges us to examine the
conditions and discuss the outlook as to the persistence of human life
and society and of the values that belong to them. It is not enough to
hope (or fear?) the rising of new forms; we have also to investigate the
possibility of upholding the forms and ideals which have hitherto been
the bases of human life. Darwin has here given his age the most earnest
and most impressive lesson. This side of Darwin's theory is of peculiar
interest to some special philosophical problems to which I now pass.

IV.

Among philosophical problems the problem of knowledge has in the last
century occupied a foremost place. It is natural, then, to ask how
Darwin and the hypothesis whose most eminent representative he is, stand
to this problem.

Darwin started an hypothesis. But every hypothesis is won by inference
from certain presuppositions, and every inference is based on
the general principles of human thought. The evolution hypothesis
presupposes, then, human thought and its principles. And not only
the abstract logical principles are thus presupposed. The evolution
hypothesis purports to be not only a formal arrangement of phenomena,
but to express also the law of a real process. It supposes, then,
that the real data--all that in our knowledge which we do not produce
ourselves, but which we in the main simply receive--are subjected
to laws which are at least analogous to the logical relations of our
thoughts; in other words, it assumes the validity of the principle of
causality. If organic species could arise without cause there would
be no use in framing hypotheses. Only if we assume the principle of
causality, is there a problem to solve.

Though Darwinism has had a great influence on philosophy considered as
a striving after a scientific view of the world, yet here is a point of
view--the epistemological--where philosophy is not only independent but
reaches beyond any result of natural science. Perhaps it will be said:
the powers and functions of organic beings only persist (perhaps also
only arise) when they correspond sufficiently to the conditions under
which the struggle of life is to go on. Human thought itself is, then, a
variation (or a mutation) which has been able to persist and to
survive. Is not, then, the problem of knowledge solved by the evolution
hypothesis? Spencer had given an affirmative answer to thi