René Descartes

René Descartes (1596–1650), French philosopher, mathematician, and natural scientist, is widely regarded as the founder of modern Western philosophy. Educated by the Jesuits at La Flèche, he combined a Catholic upbringing with a programmatic break from scholastic Aristotelianism, seeking to refound knowledge on indubitable first principles. In the Discourse on the Method (1637) and Meditations on First Philosophy (1641), he developed methodic doubt, the cogito ("I think, therefore I am"), and substance dualism between res cogitans and res extensa. Descartes advanced two principal arguments for God's existence: a causal argument from the idea of a perfect being in the finite mind, and a reworked ontological argument from God's essence to existence. Divine veracity functions as the guarantor of clear and distinct ideas and thus of scientific knowledge of the external world—generating the much-debated "Cartesian circle" first pressed by Antoine Arnauld and Pierre Gassendi in the Objections. His correspondence with Princess Elisabeth of Bohemia exposed difficulties in mind-body interaction; Spinoza, Leibniz, and Malebranche reworked his system in response. Critics from Hume to Heidegger have targeted his foundationalism, representationalism, and conception of subjectivity, while contemporary philosophy of mind continues to engage with—and largely reject—his dualism. Despite professed orthodoxy, his works were placed on the Index in 1663, reflecting tensions between his mechanistic physics, his theology, and Catholic doctrine.