René Descartes
Doubt everything to find what survives doubt.
René Descartes (1596 – 1650, France · Dutch Republic · Sweden) : rationalism. To build knowledge as solid as mathematics, Descartes resolves to [[doute-methodique|doubt everything]] that can be doubted: the senses, dreams, even proofs. One thing survives: while he doubts, he thinks, so he exists. On AskPhilosophy: 9 reconstructed arguments, 4 quotes checked word for word against the original texts, and 4 common beliefs examined; every text carries an authenticity badge (written by the author, posthumous, student notes, reported, apocryphal).
Why he matters
He is often called the father of modern philosophy: he starts from the thinking subject rather than the authority of the Ancients. As a mathematician he invented analytic geometry: the "Cartesian coordinates" still taught in school.
His times
Educated by the Jesuits at La Flèche, a soldier during the Thirty Years' War, he lived twenty years in the Dutch Republic. In 1633, hearing of Galileo's condemnation, he gave up publishing his treatise The World. He died in Stockholm, invited by Queen Christina.
His positions
click a row to see the evidenceHe proves God's existence from the idea of the infinite we find in ourselves (Med. III) and by the ontological argument (Med. V). God then guarantees the truth of our clear and distinct ideas.
The piece of wax: it is neither sight nor touch that tells us what the wax is, but "an inspection of the mind". Our fundamental ideas are innate.
Doubt is not an end but a tool: it leads to a general rule : what we conceive clearly and distinctly is true.
Cartesian dualism: mind (a thinking, unextended thing) and body (an extended, unthinking thing) are two distinct substances. See the full argument below.
The freedom of our will is known without proof: even while doubting everything, we felt we could refuse to believe. Yet he admits he cannot reconcile it with God's omnipotence.
The good is objective, but Descartes holds (Replies to the Sixth Objections, and his 1630 letters to Mersenne) that eternal truths, those about the good included, depend on God's free will; man finds them already established by God. An unusual moral realism grounded in God.
God and the soul should be demonstrated "by philosophical rather than theological reasoning". But he leaves revealed theology outside the scope of his method.
He does not address the question directly. In his letters to Elisabeth, the highest good is the contentment of mind that comes from virtue.
"Good sense is the most fairly distributed thing in the world": reason is equal in all; our errors come from misusing our will, not from a corrupt nature.
His first maxim: obey the laws and customs of his country and keep his religion. Radical doubt is for the search for truth, not for social life, and he declines to reform states.
His ethics first takes the form of "provisional maxims" (Discourse III), then culminates in generosity: the firm resolve to use one's free will well. Scholars debate how close this is to virtue ethics and Stoicism.