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Mind–body dualism
1641 (Meditations)· Idea or argument· Reality, mind & God
Well documentedSolid records, texts or physical evidence.
Descartes' view that mind and body are two different kinds of thing: a thinking, unextended soul and an extended, unthinking machine.
See it on the Philosophy map →The idea
Idea: you are a thinking thing joined to a body, and the two are different substances. Reasoning: I can doubt my body exists but not my mind; matter has size and location, thought has neither. Descartes guessed they meet at the pineal gland in the brain. Main objection, put in 1643 by Princess Elisabeth of Bohemia: how can something with no extension push a physical body? This 'interaction problem' remains the view's chief weakness.
Why it matters
It set the terms of the mind-body problem for modern thought and freed the physical world to be studied as pure mechanism, apart from the soul.
Where it comes from
Set out in the Meditations (1641) and Passions of the Soul (1649); Elisabeth's challenge survives in her 1643 letters with Descartes.
Still debated
Few philosophers or neuroscientists now accept two substances, but whether consciousness can be fully explained in physical terms is still open.
Connections (5)
▸Avicenna (Ibn Sina) anticipated, with his "flying man," Mind–body dualismMostly agreed
The connection
Avicenna imagined a man created in midair, blindfolded, limbs apart, touching nothing. He would still know he exists without knowing he has a body, so the self or soul must be distinct from the body. Descartes' argument that he can doubt his body but not his mind follows a strikingly similar path.
When and how
Avicenna's Book of Healing (al-Shifa), the part On the Soul, written in Persia in the 1020s; translated into Latin in Toledo in the 12th century.
How sure are we?
The 'flying man' was widely known to medieval Latin scholars through that translation; its parallel with Descartes' Meditations is a standard point in histories of philosophy.
Debates and open questions
Whether Descartes knew the argument, directly or through scholastic teaching at his Jesuit school, is unproven, and the two arguments serve different purposes.
▸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.
▸Mind–body dualism gives one classic answer to What is the mind?Mostly agreed
The connection
Dualism is the classic answer to what the mind is: an immaterial thinking substance, distinct from the brain and body. It fits common intuitions and many religious views of the soul, but its interaction problem pushed most later philosophers toward materialism or other alternatives.
When and how
Descartes' Meditations (1641); predecessors include Plato's Phaedo, and philosophers such as Richard Swinburne still defend versions today.
How sure are we?
In the 2020 PhilPapers survey of philosophers, about half favored physicalism and about a third non-physicalism, a camp broader than Descartes' substance dualism.
Debates and open questions
Property dualism, which says brains have non-physical properties such as experience, keeps a version alive; whether any dualism fits neuroscience is debated.
▸Mind–body dualism was rejected by Baruch SpinozaWell documented
The connection
Spinoza rejected Descartes' two substances. He argued there is only one substance, God or Nature, and that mind and body are two aspects of the same thing, like two descriptions of one event. Nothing has to cross between them, so the interaction problem disappears. This view is often called dual-aspect monism.
When and how
Spinoza's Ethics, Part 2, finished around 1675 in The Hague and published after his death in 1677; he had expounded Descartes' philosophy in 1663.
How we know
Spinoza published an exposition of Descartes' Principles (1663) and openly mocks the pineal-gland theory in the preface to Part 5 of the Ethics.
Debates and open questions
Whether Spinoza's two aspects solve the interaction problem or just rename it is debated; some neuroscientists, such as Antonio Damasio, cite him favorably.
▸Mind–body dualism foreshadowed Chalmers and the hard problem of consciousnessMostly agreed
The connection
Descartes split reality into thinking mind and extended matter, leaving a puzzle: how do physical processes connect with experience? Chalmers' hard problem is a modern restatement of that gap. His own answer, 'naturalistic dualism', treats experience as a basic feature of the world alongside physical ones, though not as a separate soul.
When and how
Descartes' Meditations (1641) set out the split; Chalmers revived the question in 1995 and in The Conscious Mind (1996), where he defends a form of property dualism.
How sure are we?
Chalmers discusses the dualist tradition directly, and his zombie argument is often compared with Descartes' argument that mind and body can be clearly conceived apart.
Debates and open questions
Many physicalists accept the hard problem's question but reject dualism; whether the problem forces any form of dualism is the main disagreement.