compact philosophical treatise of modern time. It is worthy of note,
that, writing in the desultory, fragmentary, and accidental way he
did, he not only wrote with unexampled clearness on matters the most
abstruse, but never, that we are aware, in all the variety of his
communications, extending over so many years, contradicted himself.
No philosopher is more intelligible, none more consequent.

In philosophy, Leibnitz was a _Realist_. We use that term in the
modern, not in the scholastic sense. In the scholastic sense, as we
have seen, he was not a Realist, but, from childhood up, a Nominalist.
But the Realism of the schools has less affinity with the Realism
than with the Idealism of the present day.

His opinions must be studied in connection with those of his
contemporaries.

Des Cartes, Spinoza, Locke, and Leibnitz, the four most
distinguished philosophers of the seventeenth century, represent
four widely different and cardinal tendencies in philosophy: Dualism,
Idealism, Sensualism, and Realism.

Des Cartes perceived the incompatibility of the two primary
qualities of being, thought and extension, as attributes of one and
the same (created) substance. He therefore postulated two (created)
substances,--one characterized by thought without extension, the
other by extension without thought. These two are so alien and so
incongruous, that neither can influence the other, or determine the
other, or any way relate with the other, except by direct mediation
of Deity. (The doctrine of Occasional Causes.) This is Dualism,--
that sharp and rigorous antithesis of mind and matter, which Des