François-Marie d’Arouet (1694–1778), better known by his pen name Voltaire, was a French writer and public activist who played a singular role in defining the eighteenth-century movement called the Enlightenment. At the center of his work was a new conception of philosophy and the philosopher that in several crucial respects influenced the modern concept of each. Yet in other ways Voltaire was not a philosopher at all in the modern sense of the term. He wrote as many plays, stories, and poems as patently philosophical tracts, and he in fact directed many of his critical writings against the philosophical pretensions of recognized philosophers such as Leibniz, Malebranche, and Descartes. He was, however, a vigorous defender of a conception of natural science that served in his mind as the antidote to vain and fruitless philosophical investigation. In clarifying this new distinction between science and philosophy, and especially in fighting vigorously for it in public campaigns directed against the perceived enemies of fanaticism and superstition, Voltaire pointed modern philosophy down several paths that it subsequently followed.