Contribution to Philosophy

Leibniz voluminous notebooks indicate that during the years at Hanover Leibniz's thought was increasingly dominated by the development of a comprehensive cosmic philosophy. He composed no complete exposition of his philosophical theories, but to any of his correspondents who inquired about them he freely expounded phases of his "new system," and on three important occasions he took issue with exponents of differing views in extended polemical essays which brought out the essentials of his own philosophy.

In his Théodicé, written in reply to an attack upon his views in Pierre Bayle's Dictionnaire historique et critique (1699), Leibniz defines God as "infinite possibility" and the world (actuality) as "compossibility" in that it contains the greatest number of stimultaneous possibilities; it is therefore the best of all possible worlds. In defining "substance," he proceeds from the traditional postulate that all predicates are contained in their subjects, to the designation as substances of all words which can be used only as subjects.

In a criticism of John Locke's Essay on Human Understanding (1690) Leibniz refuted Locke's major premise that the senses are the source of all understanding by adding "except the understanding itself," distinguishing three levels of understanding: the self-conscious, the conscious, and the unconscious or subconscious. And in an essay known as the "Monadology," he more specifically defines the ultimate elements of the universe as individual precipient centers of possibility or force, which he calls "monads." Each unit perceives the universe from its own point of view and interprets what it perceives according to its own level of understanding, but there is no interaction or intercommunication among the units and therefore no operation of cause and effect.

In the famous exchange of letters (1715-1716) with Samuel Clarke, Leibniz describes space and time as merely systems of relationship or order, calling Newton's treatment of them as absolute entities a reversion to medieval notions.

Such ideas as these, characteristic of Leibniz's application of logic to the problems of metaphysics, found little response among the philosophers of his time, who were more receptive to the patterns of Locke's empiricism. But when Leibniz's Nouveaux essais sur l'entendement humain was finally published in 1765, Locke's influence was receding, and Leibniz's work became a major factor in the formation of the transcendental philosophy of Immanuel Kant.