After studying at Leipzig, his native city, and at Jena, he became a doctor of law at Altdorf (1666). Constantly occupied with practical political concerns, Leibniz never accepted an academic position. He was (1666-73) in the diplomatic service of the elector of Mainz, who employed him on several political projects; one of these was a plan to persuade King Louis XIV of France to attack Egypt and thereby to divert his attention from Germany. While in Paris (1672-76) he came into contact with some of the foremost minds of Europe.
About that time he developed, independently of Newton, the infinitesimal calculus. Leibniz's calculus was published in 1684, three years before Newton's, and his system of notation was universally adopted. From 1676 he was employed by the duke of Brunswick-Lüneburg (later the elector of Hanover), whom he served as privy councillor, librarian, and historian. This association brought him close to the elector of Brandenburg (soon to be king of Prussia), who was persuaded by Leibniz to establish a scientific academy at Berlin. In 1700 he became its first president.
Most of Leibniz's philosophical writings are occasional pieces, addressed to various people. The two published in his lifetime were Essais de Théodicée sur la bonté de Dieu, la liberté de l'homme, et l'origine du mal (1710) and Monadology (1714). It was largely these works that influenced Christian von Wolff, whose popularization of the Leibnizian system became the standard academic philosophy in 18th-century Germany.
Leibniz's major philosophical work, Nouveaux Essais sur l'entendement humain (1704), contains the views of Leibniz on points raised in Locke's Essay Concerning Human Understanding. Because of Locke's death, however, it was not published until 1765. The publication of Nouveaux Essais in 1765 was important because it revealed for the first time the "true Leibniz" as opposed to the popularized version of Wolff, and it had a decisive effect on Immanuel Kant and the whole German Enlightenment.
Leibniz's philosophy is a consistent rationalism. The universe forms one context in which each occurrence can be seen in relation to every other. Since the universe is the result of a divine plan, Leibniz calls it the best of all possible worlds; for this he was satirized by Voltaire in Candide. Leibniz's assertion, however, does not imply an unqualified optimism, since evil is a necessary ingredient in even the best of all possible worlds. The ultimate constituents of the universe, in his view, are monads or simple substances, each of which represents the universe from a different point of view. Being simple, monads are immaterial and thus cannot act. Apparent interaction is explained in terms of the principle of preestablished harmony.
The principle of continuity as expressed in the phrase "nature makes no leaps" is another part of Leibniz's rationalism. The monads are arranged in an infinitely ascending scale, based on the distinctness with which each represents the universe. All monads have perception (consciousness), but only rational monads have apperception (self-consciousness). A basic distinction in Leibniz's logic is that made between "truths of reason," or necessary propositions, whose principle is the law of noncontradiction, and "truths of fact," or contingent propositions, based on the principle of sufficient reason. The principle has its root in the divine intellect, and its most important expression is his law of causality.
With the decline of interest in metaphysics in contemporary philosophy, recent studies have tended to emphasize Leibniz's significance in mathematics and logic. However, Leibniz's metaphysics have not been neglected but rather reinterpreted in light of his mathematical and logical works.
See Liebniz's political writings, ed. and tr. by P. Riley (1972); G. H. Parkinson, Logic and Reality in Leibniz's Metaphysics (1965); H. Ishiguro, Leibniz's Philosophy of Logic and Language (1972); G. M. Ross Leibniz (1984); S. Brown Leibniz (1985).