Philosopher · Early modern
René Descartes
1596–1650 · Cartesian rationalism
Died a Catholic; his works were placed on the Index donec corrigantur (1663), and Cartesianism was banned in French and Jesuit schools.
Jesuit-educated mathematician and founder of modern philosophy, Descartes sought a certainty immune to doubt and found it in the thinking self (cogito ergo sum), from which he proved God and then the external world. He held that mind and body are two complete substances, that animals are machines, that matter is pure extension, and that the eternal truths depend on God's free will. He dedicated the Meditations to the Sorbonne and remained, he insisted, a faithful Catholic.
Why he matters: His turn to the subject set the agenda of all later philosophy, and the Church's long quarrel with rationalism, idealism and dualism begins here; yet his proofs of God and the soul were offered in the service of the faith, and his piety was real.
Where to be careful
On the Index for the doctrine of matter as extension (incompatible, it was judged, with transubstantiation) and for method of doubt; his dualism is foreign to Vienne's definition of the soul as form of the body, and his voluntarism about eternal truths unsettles the natural law.
Reading
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Meditations on First Philosophy, with Objections and RepliesRené Descartes · Read the Objections of Arnauld and Gassendi with it; the Church's worries are there.
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Discourse on MethodRené Descartes · The short autobiographical version.
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The Unity of Philosophical ExperienceÉtienne Gilson · Chapters on “The Cartesian Experiment”; the classic Catholic diagnosis.
Documented positions
Where this thinker stands on each dispute the test covers.