d 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 pre-supposed. 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 subject 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 this
question before the appearance of _The Origin of Species_. For the
individual, he said, there is an _a priori_, original, basis (or
_Anlage_) for all mental life; but in the species