It has no natural affinity with the more "ideal" or "spiritual" form of Pantheism. We must not conclude, however, that it has no historical connection with it. For it is instructive to mark, in tracing the history of philosophic speculation, that its course resembles not so much the uniform current of a stream, as the alternate flowing and ebbing of the tide; or, if we may change the figure, that its movement may be likened to the oscillation 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 efficient or final, from the field of