 Gilles Deleuze (January 18, 1925–November 4, 1995) was one of the most influential and prolific French philosophers of the second half of the twentieth century. Deleuze conceived of philosophy as the production of concepts, and he characterized himself as a “pure metaphysician.” In his magnum opus Difference and Repetition, he tries to develop a metaphysics adequate to contemporary mathematics and science—a metaphysics in which the concept of multiplicity replaces that of substance, event replaces essence and virtuality replaces possibility. Deleuze also produced studies in the history of philosophy (on Hume, Nietzsche, Kant, Bergson, Spinoza, Foucault, and Leibniz), and on the arts (a two-volume study of the cinema, books on Proust and Sacher-Masoch, a work on the painter Francis Bacon, and a collection of essays on literature.) Deleuze considered these latter works as pure philosophy, and not criticism, since he sought to create the concepts that correspond to the artistic practices of painters, filmmakers, and writers. In 1968, he met Félix Guattari, a political activist and radical psychoanalyst, with whom he wrote several works, among them the two-volume Capitalism and Schizophrenia, comprised of Anti-Oedipus (1972) and A Thousand Plateaus (1980). Their final collaboration was What is Philosophy? (1991).