It has been the object of the preceding paragraphs to show that Leibniz[11] the politician and Leibniz the theologian were one and the same person; not at all to suggest that his rational theology was just political expediency.  We may apply to him a parody of his own doctrine, the pre-established harmony between nature and grace.  Everything happens as though Leibniz were a liberal politician, and his theology expressed his politics.  Yes, but equally, everything happens as though Leibniz were a philosophical theologian, and his politics expressed his theology.  His appreciation of Catholic speculation was natural and sincere; his dogmatic ancestry is to be looked for in Thomism and Catholic humanism as much as anywhere.  Above all, he had himself a liberal and generous mind.  It gave him pleasure to appreciate good wherever he could see it, and to discover a soul of truth in every opinion.

From the moment when Leibniz became aware of himself as an independent thinker, he was the man of a doctrine.  Sometimes he called it ’my principles’, sometimes ‘the new system’, sometimes ’pre-established harmony’.  It could be quite briefly expressed; he was always ready to oblige his friends with a summary statement, either in a letter or an enclosed memorandum, and several such have come down to us.  The doctrine may have been in Leibniz’s view simple, but it was applicable to every 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.