rial which he collected by his observations and his experiments.
He not only revived an old hypothesis, but he saw the necessity of
verifying it by facts. Whether the special cause on which he founded the
explanation of the origin of species--Natural Selection--is sufficient,
is now a subject of discussion. He himself had some doubt in regard
to this question, and the criticisms which are directed against his
hypothesis hit Darwinism rather than Darwin. In his indefatigable search
for empirical evidence he is a model even for his antagonists: he has
compelled them to approach the problems of life along other lines than
those which were formerly followed.

Whether the special cause to which Darwin appealed is sufficient or not,
at least to it is probably due the greater part of the influence which
he has exerted on the general trend of thought. "Struggle for existence"
and "natural selection" are principles which have been applied, more or
less, in every department of thought. Recent research, it is true, has
discovered greater empirical discontinuity--leaps, "mutations"--whereas
Darwin believed in the importance of small variations slowly
accumulated. It has also been shown by the experimental method, which
in recent biological work has succeeded Darwin's more historical method,
that types once constituted possess great permanence, the fluctuations
being restricted within clearly defined boundaries. The problem has
become more precise, both as to variation and as to heredity. The inner
conditions of life have in both respects shown a greater independence
than Darwin had supposed in his theory, though he always admitted that
the cause of variation was to him a great enigma, "a most perplexing
problem," and that the struggle for life could only occur where
variation existed. But, at any rate, it was of the greatest importance
that Darwin gave a living impression of the struggle for life which is
everywhere going on, and to which even the highest forms of existence
must be amenable. The philosophical importance of these ideas does not
stand or fall with the answer to the question, whether natural selection
is a sufficient explanation of the origin of species or not: it has
an independent, positive value for everyone who will observe life and
reality with an unbiassed mind.

In accentuating the struggle for life Darwin stands as a
characteristically English thinker: he continues a train of ideas which
Hobbes and Malthus ha