department of human speculation or enquiry. It provided a new alphabet of
philosophical ideas, and everything in heaven and earth could be expressed
in it; not only could be, but ought to be, and Leibniz showed tireless
energy in working out restatements of standing problems.

As a man with an idea, with a philosophical nostrum, Leibniz may be
compared to Bishop Berkeley. There was never any more doubt that Leibniz
was a Leibnitian than that Berkeley was a Berkeleian. But there is no
comparison between the two men in the width of their range. About many
things Berkeley never took the trouble to Berkeleianize. To take the most
surprising instance of his neglect--he assured the world that his whole
doctrine pointed to, and hung upon, theology. But what sort of a theology?
He scarcely took the first steps in the formulation of it. He preferred to
keep on defending and explaining his _esse est percipi_. With Leibniz it is
wholly different; he carries his new torch into every corner, to illuminate
the dark questions.

The wide applicability of pre-established harmony might come home to its
inventor as a rich surprise. The reflective historian will find it less[12]
surprising, for he will suspect that the applications were in view from the
start. What was Leibniz thinking of when the new principle flashed upon
him? What was he _not_ thinking of? He had a many-sided mind. If the
origins of the principle were complex, little wonder that its applications
were manifold. Every expositor of Leibniz who does not wish to be endlessly
tedious must concentrate attention on one aspect of Leibniz's principle,
and one source of its origin. We will here give an account of the matter
which, we trust, will go most directly to the heart of it, but we will make
no claims to sufficient interpretation of Leibniz's thought-processes.

Leibniz, then, like all the philosophers of the seventeenth century, was