educates the power of abstract thought. Every science is a model of
method, a discipline in close and consecutive thinking; and this merit
Logic ought to possess in a high degree.

For ages Logic has served as an introduction to Philosophy that is, to
Metaphysics and speculative Ethics. It is of old and honourable
descent: a man studies Logic in very good company. It is the warp upon
which nearly the whole web of ancient, mediæval and modern Philosophy is
woven. The history of thought is hardly intelligible without it.

As the science of proof, Logic gives an account of the _general_ nature
of evidence deductive and inductive, as applied in the physical and
social sciences and in the affairs of life. The _general_ nature of such
evidence: it would be absurd of the logician to pretend to instruct the
chemist, economist and merchant, as to the _special_ character of the
evidence requisite in their several spheres of judgment. Still, by
investigating the general conditions of proof, he sets every man upon
his guard against the insufficiency of evidence.

One application of the science of proof deserves special mention:
namely, to that department of Rhetoric which has been the most
developed, relating to persuasion by means of oratory, leader-writing,
or pamphleteering. It is usually said that Logic is useful to convince
the judgment, not to persuade the will: but one way of persuading the
will is to convince the judgment that a certain course is advantageous;
and although this is not always the readiest way, it is the most
honourable, and leads to the most enduring results. Logic is the
backbone of Rhetoric.

It has been disputed whether Logic is a science or an art; and, in fact,