Gilson Étienne (1884–1978), French Catholic philosopher, historian, cofounder of the Pontifical Institute of Medieval Studies in Toronto, and a major figure in Neo-Thomism. Gilson discovered medieval philosophy through his pioneering work on Descartes’s Scholastic background. As a historian, he argued that early modern philosophy was incomprehensible without medieval thought, and that medieval philosophy itself did not represent the unified theory of reality that some Thomists had supposed. His studies of Duns Scotus, Augustine, Bernard, Aquinas, Bonaventure, Dante, and Abelard and Héloïse explore this diversity. But in his Gifford lectures (1931–32), The Spirit of Medieval Philosophy, Gilson attempted a broad synthesis of medieval teaching on philosophy, metaphysics, ethics, and epistemology, and employed it in his critique of modern philosophy, The Unity of Philosophical Experience (1937). Most of all, Gilson attempted to reestablish Aquinas’s distinction between essence and existence in created being, as in Being and Some Philosophers (1949). See also NEO -THOMISM , THOMIS. D.W.H.