e, then night may be said to be the cause of day,
for the one invariably precedes the other. Day does succeed to night,
but only on certain conditions--namely, that the sun rise. "The
succession," observes Mr Mill, "which is equivalent and synonymous to
cause, must be not only invariable but unconditional. We may define,
therefore," says our author, "the cause of a phenomenon to be the
antecedent, or the concurrence of antecedents, upon which it is
invariably and _unconditionally_ consequent."--Vol. I. p. 411.

A dilemma may be raised of this kind. The universality of the law of
causation--in other words, the uniform course of nature--is the
fundamental principle on which all induction proceeds, the great
premise on which all our science is founded. But if this law itself be
the result only of experience, itself only a great instance of
induction, so long as nature presents cases requiring investigation,
where the causes are unknown to us, so long the law itself is
imperfectly established. How, then, can this law be a guide and a
premiss in the investigations of science, when those investigations
are necessary to complete the proof of the law itself? How can this
principle accompany and authorise every step we take in science, which
itself needs confirmation so long as a process of induction remains to
be performed? Or how can this law be established by a series of
inductions, in making which it has been taken for granted?

Objections which wear the air of a quibble have often this
advantage--they put our knowledge to the test. The obligation to find
a complete answer clears up our own conceptions. The observations
which Mr Mill makes on this point, we shall quote at length. They are
taken from his chapter on the _Evidence of the Law of Universal
Causation_; the views in which are as much distinguished for boldness
as for precision.

After having said, that in all the several methods of induction the
universality of the law of causation is assumed, he continues:--

"But is this assumption warranted? Doubtless (it may be
said) _most_ phenomena are connected as effects with
some antecedent or cause--that is, are never produced
unless some assignable fact has preceded them; but the
very circumstance, that complicated processes of
induction are sometimes necessary, shows that cases
exist in which this regular order of succession is not
apparent to our first and simplest apprehension. If,