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
phaenomena, is called, in its most general expression, the deductive method,
and consists of three operations: the first, one of direct induction; the
second, of ratiocination; and the third, of verification."

Now, the conditions which have determined the existence of species are not
only exceedingly complex, but, so far as the great majority of them are
concerned, are necessarily beyond our cognisance. But what Mr. Darwin has
attempted to do is in exact accordance with the rule laid down by Mr. Mill;
he has endeavoured to determine certain great facts inductively, by
observation and experiment; he has then reasoned from the data thus
furnished; and lastly, he has tested the validity of his ratiocination by
comparing his deductions with the observed facts of Nature. Inductively,
Mr. Darwin endeavours to prove that species arise in a given way.
Deductively, he desires to show that, if they arise in that way, the facts
of distribution, development, classification, &c., may be accounted for,
_i.e._ may be deduced from their mode of origin, combined with