Letter of Dedication
The letter to the Sorbonne
Descartes addresses the dean and doctors of the sacred faculty of theology in Paris. He has two things he wants philosophy to prove by natural reason: that God exists, and that the soul is distinct from the body. He notes that Scripture says the knowledge of God is clear enough that those who lack it are blameworthy — which implies a philosophical proof should be possible. He has already sketched the argument in the Discourse on the Method of 1637; now he offers a fuller treatment and asks for the Sorbonne's protection. The political stakes are real: Descartes watched Galileo condemned by the Roman Inquisition in 1633 and chose the Netherlands as his base precisely to write freely. The dedication is not mere flattery but a calculated move.
Preface to the Reader
Preface and pre-emptive replies
In the Discourse on the Method, Descartes had asked readers to point out anything worthy of objection. Two objections came back, and he addresses them here. The first: even if the mind perceives itself as nothing but a thinking thing, it does not follow that its nature consists only in being a thinking thing — the word "only" might be too strong. The second: even if I have the idea of something more perfect than I am, it does not follow that the idea itself, or its object, actually exists. Both objections are addressed briefly but precisely. Descartes then tells the reader what to expect: the meditations require sustained concentration over several days, and the reader should not judge any single one in isolation.
Synopsis
The roadmap
The Synopsis describes each meditation in a single paragraph. The First establishes the grounds for doubting everything. The Second shows that the mind's existence is the one thing that survives total doubt. The Third proves God exists from the idea of God in the mind. The Fourth explains truth, error, and why a perfect God is compatible with a creature who makes mistakes. The Fifth gives a second proof of God from the nature of essence. The Sixth proves the existence of bodies and establishes the real distinction between mind and body. The Synopsis is not a substitute for the meditations; Descartes says explicitly that the soul's immortality, which many expect him to prove, is not in fact demonstrated here — it requires further premises from physics. The map tells you where you are going but not what you will find when you get there.
Meditation 1
The great demolition
Meditation 1 is the controlled demolition. Descartes has decided that once in his life he will rid himself of all opinions received without examination, and he must do it now while he is free from the cares of practical life. He does not need to show every belief is false — only that it might be. First wave: the senses sometimes mislead. Second wave: even clear sensory experience might be dreaming. Third wave: even arithmetic and logic might be wrong if an evil deceiver has constructed my mind to treat falsehoods as truths. At the end, Descartes has no secure ground left. He resolves to hold to the doubt deliberately, as if all familiar beliefs were false, so that he can proceed to what — if anything — the doubt cannot touch.
Meditation 2
The cogito and the wax
Meditation 2 opens in the wreckage left by the First. Descartes supposes all the things he sees are false; he has no senses; body, shape, extension, and motion are fictions. But wait — if he is being deceived, he must exist to be deceived. Whatever else is uncertain, the thinking, doubting self exists: cogito, ergo sum. Next he asks what kind of thing this self is. Not a body — he has not yet established that bodies exist. He is, essentially, a thing that thinks: that doubts, understands, affirms, denies, wills, refuses, imagines, perceives. Then the wax argument: a piece of wax loses every sensible quality when held near flame, yet he judges it to be the same wax. The judgment comes from the mind, not the senses. The mind is more immediately known than any body.
Meditation 3
The proof of God from the idea of God
Meditation 3 is the most demanding of the six. Descartes begins by taking stock of what he knows: he is a thinking thing, and whatever he perceives clearly and distinctly is probably true — but he cannot be fully certain until he has dealt with the possibility of a deceiving God. He then launches into a lengthy examination of the kinds of ideas in the mind and their "objective reality" — the degree of being they represent. The key move: the idea of God in my mind represents an infinite, all-perfect being. Nothing finite and imperfect could be the adequate cause of an idea with that much objective reality. Therefore an actually existing infinite and perfect being — God — must have caused the idea. This is the trademark argument. God exists. And a perfect God would not be a deceiver. Therefore clear and distinct perception is reliable. The circle of knowledge begins to close.
Meditation 4
Why we make mistakes
Meditation 4 is short and underestimated. Descartes now knows God is not a deceiver and that his faculties, used correctly, are reliable. But he still makes mistakes. Why? The intellect has a limited range: it clearly perceives some things, dimly perceives others, and perceives nothing at all of yet others. The will, by contrast, is unlimited — it can assent to or dissent from anything that comes before the mind. Error arises when the will extends itself beyond the range of the intellect: when I affirm something I do not clearly and distinctly understand. The remedy is not to distrust the intellect but to discipline the will: withhold assent from anything not clearly perceived. Right cognition is an exercise of self-government.
Meditation 5
The ontological proof
Meditation 5 is in two parts. The first examines the clear and distinct ideas of mathematical objects — triangles, spheres, numbers — and argues that these objects have true and immutable natures even if no such objects exist in the world. (I can discover properties of a triangle I did not put there.) The second part gives the ontological argument: I have the idea of a supremely perfect being. Existence is a perfection. Therefore existence is contained in the idea of a supremely perfect being; therefore God exists. The argument is not that I can imagine existence into anything — I cannot conceive a mountain without a valley, but that proves nothing about whether mountains exist. The case of God is different: existence belongs to the nature of a perfect being necessarily, the way having three angles belongs necessarily to a triangle.
Meditation 6
The return to the world
The last meditation is the longest and the most resolved. Bodies exist — not because the senses are trustworthy, but because God, who is not a deceiver, would not have given us such a powerful inclination to believe in them if they did not exist. The mind is really distinct from the body: I have a clear and distinct idea of myself as a thinking, non-extended thing, and a clear and distinct idea of body as extended, non-thinking — and what I clearly and distinctly conceive as separable, God can produce as separate. But then Descartes admits the twist: mind and body are also intimately united. Pain is not a cold observation of damage — I feel it. This is the union. And the union is real, even though the distinction is real. The puzzle Descartes ends on — how can two wholly different substances interact? — is the puzzle that has not been solved since.