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René Descartes
1596–1650· Philosopher· Reality, mind & God
Well documentedSolid records, texts or physical evidence.
French philosopher and mathematician who tried to rebuild all knowledge from one certain starting point; often called the father of modern philosophy.
See it on the Philosophy map →The idea
Idea: doubt everything that can be doubted, then rebuild only on what survives. Jesuit-educated, briefly a soldier, he lived mostly in the Dutch Republic. Discourse on the Method (1637) and Meditations (1641) doubt the senses, dreams and even arithmetic, reach the cogito, then argue for God and an outside world. He and Fermat independently invented coordinate geometry, the x–y graph. Main objection: his road back from doubt depends on God, a step critics since Arnauld call circular.
Why it matters
He made 'how do I know?' the first question of philosophy for two centuries, and split reality into mind and matter, a picture still argued over.
Legacy and sources
His books and letters survive, and the Meditations was printed with objections from Hobbes, Gassendi, Arnauld and others, plus his replies. He died in Stockholm in 1650 while tutoring Queen Christina.
Still debated
Most historians say he died of pneumonia; a 2009 book by Theodor Ebert argued arsenic poisoning, which few accept.
Inside this (6)
Connections (10)
▸Ancient Skepticism (Pyrrho to Sextus Empiricus) was answered by René DescartesMostly agreed
The connection
Ancient Skeptic arguments, revived in print in the 1560s, threatened all certainty: the senses deceive and dreams feel real. Descartes turned their method into a tool, doubting everything on purpose to find what could not be doubted, the cogito, then rebuilding knowledge on it as his answer to the skeptics.
When and how
Henri Estienne printed Sextus Empiricus in Latin in 1562; Descartes answered in the Meditations, published in Paris in 1641.
How sure are we?
The First Meditation uses classic skeptical arguments, and Descartes' replies discuss skeptics directly; historian Richard Popkin documented this 'skeptical crisis' of the period.
Debates and open questions
Many think Descartes failed to beat the skeptics, since his road back from doubt depends on proving God; whether he ever truly doubted is also debated.
▸Anselm's ontological argument was revived by René DescartesWell documented
The connection
Anselm argued that God, 'that than which nothing greater can be conceived', must exist. Aquinas rejected the argument, but Descartes revived a version: existence belongs to the idea of a supremely perfect being as inseparably as a valley belongs to the idea of a mountain, so God exists.
When and how
Anselm's Proslogion (1077–78), at Bec in Normandy; Descartes' Fifth Meditation, published in Paris in 1641.
How we know
The Fifth Meditation states the argument, and the theologian Caterus, in the first set of Objections, compared it to Anselm's and raised Aquinas's criticism.
Debates and open questions
Whether Descartes' version is really Anselm's or a new argument, and whether either works, is debated; Kant later objected that existence is not a property.
▸Michel de Montaigne, Essays influenced René DescartesWell documented
The connection
Montaigne's Essays revived ancient skepticism, asking 'What do I know?' (Que sais-je?) and showing how custom shapes belief. Descartes read him and adopted his first-person, doubting voice, but aimed to defeat doubt and reach certainty, where Montaigne was content to live with it.
When and how
Montaigne wrote in his tower near Bordeaux, publishing the Essays from 1580 to 1595; Descartes' Discourse on the Method appeared in Leiden in 1637.
How we know
The Discourse echoes passages of the Essays, and Descartes discusses Montaigne's views on animals in a 1646 letter to the Marquess of Newcastle.
Debates and open questions
How far Descartes was answering Montaigne and his follower Pierre Charron specifically, rather than skepticism in general, is debated.
▸Galileo and the trial of 1633 frightened René DescartesWell documented
The connection
In 1633 the Roman Inquisition condemned Galileo for teaching that the Earth moves. Descartes, about to publish The World, which also had the Earth move, withdrew it at once. He later published his physics cautiously, and The World appeared only after his death.
When and how
Galileo was condemned in Rome in June 1633; Descartes, living in the Dutch Republic, heard the news that November.
How we know
Descartes' November 1633 letter to Mersenne says he almost burned his papers on hearing of Galileo's condemnation; The World was finally published in 1664.
Debates and open questions
How much fear, versus a wish to avoid controversy and stay in the Church's good graces, drove his caution is debated.
▸René Descartes proposed "I think, therefore I am" (the cogito)Well documented
The connection
Searching for one truth beyond doubt, Descartes doubted his senses, his body and even mathematics, imagining an all-powerful deceiver. He found that the act of doubting proved his own existence as a thinking thing, and made this cogito the first stone of his whole system.
When and how
First in French in the Discourse on the Method (Leiden, 1637), then argued fully in the Meditations (Paris, 1641) and put in Latin in the Principles (1644).
How we know
Descartes' texts state it repeatedly, and Hobbes, Gassendi and Arnauld debated it in the printed Objections and Replies.
Debates and open questions
Whether he truly built on it alone, or smuggled in other assumptions such as what 'thinking' and 'existing' mean, is debated.
▸René Descartes defended Mind–body dualismWell documented
The connection
From the cogito Descartes reasoned that he knows he is a thinking thing before knowing he has a body, and that he can clearly conceive mind without body. Since God can create whatever we clearly conceive, mind and body must be separate substances, joined in a human being.
When and how
Meditations II and VI (1641); refined in letters with Princess Elisabeth of Bohemia (1643) and in Passions of the Soul (1649).
How we know
The Sixth Meditation states the 'real distinction' argument explicitly, and Gassendi, Arnauld and Elisabeth attacked it in writing.
Debates and open questions
A standard objection, pressed by Arnauld in 1641: being able to conceive mind without body does not show they can actually exist apart.
▸René Descartes sharpened What is the mind?Mostly agreed
The connection
Before Descartes, most thinkers, following Aristotle, treated the soul as the form or life of the body. By splitting thinking mind from mechanical body, Descartes turned the question into a sharp puzzle: how two utterly different things interact, and what consciousness is in a world of matter.
When and how
Meditations on First Philosophy, Paris, 1641, and Passions of the Soul, 1649, debated across Europe through his printed objections and letters.
How sure are we?
Philosophy-of-mind textbooks start with Descartes, and 'Cartesian dualism' names the view most later theories define themselves against.
Debates and open questions
Some argue Descartes invented a false problem by separating mind and body at all; others say he only made an old puzzle explicit.
▸René Descartes was opposed by British empiricismWell documented
The connection
Descartes held that some ideas, such as God, the self and mathematics, are innate, and that reason alone can reach certain knowledge. Locke opened his Essay by attacking innate ideas, arguing that the mind starts blank and every idea comes from experience. That clash defined the later 'rationalist versus empiricist' story.
When and how
Locke's Essay Concerning Human Understanding, London, 1689, Book 1; Locke had read Descartes at Oxford in the 1660s.
How we know
According to his friend Lady Masham, Locke said Descartes' books first gave him a taste for philosophy; Book 1 of the Essay argues against innate ideas, though rarely naming Descartes.
Debates and open questions
Locke's target may have been English Platonists and schoolmen more than Descartes, and the two shared more assumptions than the textbook split suggests.
▸Nick Bostrom: superintelligence and the simulation argument updated the evil-demon doubt of René DescartesMostly agreed
The connection
Descartes imagined an evil demon feeding him a false world, to find what cannot be doubted. Bostrom's simulation hypothesis gives that doubt a technological form: our experiences could be generated by a computer run by an advanced civilization, a demon made of hardware. Unlike Descartes, Bostrom argues it may be probable, not merely possible.
When and how
Descartes' Meditations (1641), First Meditation; Bostrom's 'Are You Living in a Computer Simulation?' (2003). Hilary Putnam's brain in a vat (1981) bridged them.
How sure are we?
Commentators routinely draw the comparison, but Bostrom says his argument differs from classic skepticism, so this is a family resemblance rather than direct borrowing.
Debates and open questions
Descartes used God to escape the doubt. Whether anything rescues knowledge if we are simulated, or whether a simulated world is still real, as Chalmers argues, is debated.
▸Blaise Pascal and the wager rejected the "God of the philosophers" of René DescartesMostly agreed
The connection
Pascal respected Descartes' science but rejected his rational route to God. For Pascal, God is known by the heart and faith, not proofs: his Memorial praises the 'God of Abraham, God of Isaac, God of Jacob, not of the philosophers and scholars', and the Pensées call Descartes 'useless and uncertain'.
When and how
Pascal met Descartes in Paris in September 1647; the Memorial is dated 23 November 1654; the Pensées were published in 1670.
How sure are we?
The Pensées criticize Descartes by name; the famous complaint that Descartes needed God only for a 'flick' to start the world was recorded by Pascal's circle.
Debates and open questions
Descartes later claimed he suggested Pascal's 1648 air-pressure experiment on the Puy de Dôme; who deserves the credit, and how much rivalry colored Pascal's view, is disputed.