A French philosopher, born at Langres, the son of a cutler there; a zealous propagator of the philosophic ideas of the 18th century, and the projector of the famous "Encyclopédie," which he edited along with D'Alembert, and which made a great noise in its day, but did not enrich its founder, who was in the end driven to offer his library for sale to get out of the pecuniary difficulties it involved him in, and he would have been ruined had not Catharine of Russia bought it, which she not only did, but left it with him, and paid him a salary as librarian. Diderot fought hard to obtain a hearing for his philosophical opinions; his first book was burnt by order of the parlement of Paris, while for his second he was clapped in jail; and all along he had to front the most formidable opposition, so formidable that all his fellow-workers were ready to yield, and were only held to their task by his indomitable resolution and unquenchable ardour. "A deist in his earlier writings," says Schwegler, "the drift of his subsequent writings amounts to the belief that all is God. At first a believer in the immateriality and immortality of the soul, he peremptorily declares at last that only the race endures, that individuals pass, and that immortality is nothing but life in the remembrance of posterity; he was kept back, however, from the materialism his doctrines issued in by his moral earnestness"; that Diderot was at heart no sceptic is evident, as Dr. Stirling suggests, from his "indignation at the darkness, the miserable ignorance of those around him, and his resolution to dispel it" (1713-1784).