n of a pendulum, which no sooner reaches
its highest elevation on the one side, than it acquires a tendency to
rush to the opposite extreme on the other. There can be little doubt
that the recent revival of speculative "Idealism" was the result, at
least in part, of a strong reaction against the "sensational"
philosophy, which had degenerated in the school of Priestley at home,
and in that of Condillac abroad, into a system of gross and revolting
Materialism. For the same reason, we may now, I think, anticipate a
speedy reaction the other way,--a reaction against the extravagances of
"idealistic" and "transcendental" speculation, and a tendency towards a
more practical and matter-of-fact philosophy. This tendency, if guided
by the true spirit of the Baconian method, may give a powerful impulse
to Inductive Science in all its departments; but, if biased by partial
and one-sided views, may issue either in the temporary ascendancy of the
Positive School, or the partial revival of some other form of
Materialism.

Some such tendency might have been expected to arise as soon as Idealism
should have reached its culminating point. For, on a comprehensive view
of the whole history of speculative thought, we find that there are just
_four_ great systems of Metaphysics, which are perpetually recurring, as
it were, in cycles. The first is the system of Dualism,--not the Dualism
of Christian Theology, which speaks of God and nature, the Creator and
the creature,--but the Dualism of ancient Paganism, which held Matter
and Spirit to be equally uncreated and eternal: the second is
Materialism, which resolves all into Matter and its laws: the third is
Idealism, which resolves all into Mind and its modifications: and the
fourth is Pantheism, which identifies Existence with Thought, and
resolves all into the Absolute.[145] In the present age, Idealism is in
the ascendant, and has risen to the height of Pantheism; but, by a
natural reaction, many are beginning to desiderate a more substantial
and practical philosophy, while the rapid progress of physical science
is directing their thoughts more and more to the wonders of the material
world. In these circumstances, there may be a tendency to relapse into
the Materialism of the last century, which attempted to explain the
whole theory of the universe by the laws of _matter_ and _motion_; or at
least to embrace some modification of the Positive Philosophy, which
excludes all _causes_, whether