LEIBNIZ, although one of the great system-makers among
philosophers, did not leave a complete and full-scale account
of his philosophy. He wrote voluminously but unsystematic-
ally, and much of his work was produced in response to a book
or article with which he was in disagreement. The Théodicée,
for instance, was provoked by Bayle Dictionary article on
the difficulties of combining in a Christian theology God's
goodness, human freedom, and the existence of evil. This was
the only book published by Leibniz in his lifetime, though he
contributed articles to the learned journals of his day, Acta
Eruditorum, the Journal des Savants, etc. The rest of Leibniz's
writings were left in manuscript form in the Royal Library at
Hanover, and editors have published selections from them at
intervals. The total impression of Leibniz's work is of an
extremely condensed statement of a philosophical position
brilliantly illuminated from many points of view, from mathe-
matical and physical studies, from reflection upon morals and
religion, upon common-sense perception and microscopic
vision. This is perhaps not unfitting for a philosophy of
Monads enjoying an infinite variety of systematically inter-
connected points of view. This study is from a philosophical
standpoint which is sympathetic to, but not uncritical of,
metaphysical speculation.

I am happy to have this opportunity of thanking the editor
of the series, Professor A. J. Ayer, for the time and trouble he
has spent in reading and commenting upon this book in
manuscript, and for his many helpful criticisms and sugges-
tions. I wish also to thank my sister, Mrs Grace A. Moss, for
her help in enabling me to follow Leibniz's contribution to
mathematics.

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