e objection, that
it is preposterous to trouble ourselves about the history of the Roman
Empire, because we do not know anything positive about the origin and
first building of the city of Rome! Would it be a fair objection to
urge, respecting the sublime discoveries of a Newton, or a Kepler,
those great philosophers, whose discoveries have been of the profoundest
benefit and service to all men,--to say to them--"After all that you
have told us as to how the planets revolve, and how they are maintained
in their orbits, you cannot tell us what is the cause of the origin of
the sun, moon, and stars. So what is the use of what you have done?"
Yet these objections would not be one whit more preposterous than the
objections which have been made to the 'Origin of Species.' Mr. Darwin,
then, had a perfect right to limit his inquiry as he pleased, and the
only question for us--the inquiry being so limited--is to ascertain
whether the method of his inquiry is sound or unsound; whether he has
obeyed the canons which must guide and govern all investigation, or
whether he has broken them; and it was because our inquiry this evening
is essentially limited to that question, that I spent a good deal of
time in a former lecture (which, perhaps, some of you thought might
have been better employed), in endeavouring to illustrate the method
and nature of scientific inquiry in general. We shall now have to put in
practice the principles that I then laid down.

I stated to you in substance, if not in words, that wherever there
are complex masses of phenomena to be inquired into, whether they be
phenomena of the affairs of daily life, or whether they belong to the
more abstruse and difficult problems laid before the philosopher, our
course of proceeding in unravelling that complex chain of phenomena with
a view to get at its cause, is always the same; in all cases we must
invent an hypothesis; we must place before ourselves some more or less
likely supposition respecting that cause; and then, having assumed an
hypothesis, having supposed cause for the phenomena in question, we must
endeavour, on the one hand, to demonstrate our hypothesis, or, on the
other, to upset and reject it altogether, by testing it in three ways.
We must, in the first place, be prepared to prove that the supposed
causes of the phenomena exist in nature; that they are what the
logicians call 'vera causae'--true causes;--in the next place, we
should be prepared to show