Cartesianism

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Cartesianism is the body of philosophy descending from René Descartes (1596–1650): a program built on systematic doubt, a sharp division between thinking mind and extended matter, and a mechanical account of the physical world. It names both Descartes’s own work and the school that took up his terms across the later seventeenth century, often pressing them to conclusions he had not drawn.

The starting move was to doubt everything that could be doubted, and to see what survived. What survived, Descartes held, was the fact of his own thinking — the one thing that could not be doubted away, since doubting is itself a kind of thought. From that fixed point he rebuilt: a self whose essence is thought, a God whose existence guarantees that clear and distinct ideas are trustworthy, and beyond them a material world knowable through reason rather than the unreliable senses. The method was as much the legacy as any single conclusion; it offered a way of proceeding that owed nothing to inherited authority.

At the center sits the division usually called dualism. Mind is thinking and unextended; body is extended and unthinking; the two are really distinct substances. From this it followed that everything material — the heavens, the weather, the living body itself — could in principle be explained as matter in motion, machinery without hidden purposes or occult sympathies. That mechanical picture was Cartesianism’s most consequential export, and it set the frame against which much of early modern science, and a good deal of later esoteric thought, would define itself. The standing difficulty was the seam between the two substances: if mind and body share nothing, how does a decision move an arm, or an injury reach the soul as pain? Descartes located the meeting in the brain and left the mechanism obscure.

His successors took the problem and ran. Nicolas Malebranche held that mind and body do not interact at all; God alone acts, occasioning the appropriate effect on each occasion — the doctrine known as occasionalism. Arnold Geulincx reached a kindred view. Others extended the mechanical physics or defended the proofs of God against the period’s mounting objections, while Spinoza and Leibniz, schooled in Cartesian terms, built systems meant to heal the very split Descartes had opened.

Cartesianism was contested from the first. Critics charged that a wholly mechanical nature drained the world of life and the body of soul, and that the gap between substances could not be honestly bridged. Anne Conway, writing near the end of the century, argued against both Descartes and Hobbes that spirit and matter are not two kinds of thing but one substance in differing degrees — a vitalist reply that the library preserves in its 1692 form. The school as a movement faded as Newtonian physics and British empiricism gained ground. Its central questions did not: the relation of mind to body, and the reach of a mechanical explanation of nature, remain live where it left them.

→ In the library: Conway — The Principles of the Most Ancient and Modern Philosophy (1692)

→ Related: Dualism · Neoplatonism