hypothesis has the merit of being eminently simple and
comprehensible in principle, and its essential positions may be stated
in a very few words: all species have been produced by the development
of varieties from common stocks; by the conversion of these, first into
permanent races and then into new species, by the process of NATURAL
SELECTION, which process is essentially identical with that artificial
selection by which man has originated the races of domestic animals--the
STRUGGLE FOR EXISTENCE taking the place of man, and exerting, in the
case of natural selection, that selective action which he performs in
artificial selection.

The evidence brought forward by Mr. Darwin in support of his hypothesis
is of three kinds. First, he endeavours to prove that species may be
originated by selection; secondly, he attempts to show that natural
causes are competent to exert selection; and thirdly, he tries to prove
that the most remarkable and apparently anomalous phenomena exhibited by
the distribution, development, and mutual relations of species, can be
shown to be deducible from the general doctrine of their origin, which
he propounds, combined with the known facts of geological change; and
that, even if all these phenomena are not at present explicable by it,
none are necessarily inconsistent with it.

There cannot be a doubt that the method of inquiry which Mr. Darwin
has adopted is not only rigorously in accordance with the canons of
scientific logic, but that it is the only adequate method. Critics
exclusively trained in classics or in mathematics, who have never
determined a scientific fact in their lives by induction from experiment
or observation, prate learnedly about Mr. Darwin's method, which is not
inductive enough, not Baconian enough, forsooth, for them. But even if
practical acquaintance with the process of scientific investigation
is denied them, they may learn, by the perusal of Mr. Mill's admirable
chapter "On the Deductive Method," that there are multitudes of
scientific inquiries in which the method of pure induction helps the
investigator but a very little way.

"The mode of investigation," says Mr. Mill, "which, from the proved
inapplicability of direct methods of observation and experiment, remains
to us as the main source of the knowledge we possess, or can acquire,
respecting the conditions and laws of recurrence of the more complex
phenomena, is called, in its most general expression, the dedu