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. Where the schools had taught the soul to read truth off the surfaces of things, Cartesianism turned the order inside out: the mind first secures itself, then God, and only then the world. Certainty runs from the inside out, and the senses, demoted, no longer testify to what matter is — they merely flag that something is there.

The architecture of the system

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. The distinction is not a matter of degree or of two faculties in one nature but of two utterly different kinds of being, each fully itself without the other. 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. Animals, having no thinking substance, were on this account automata; the human body too, a hydraulic engine of nerves and fluids, ran by the same laws that move the planets. 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 contrast that sharpens it most is the living nature it displaced. The Paracelsian world was full of signatures, sympathies, and active virtues seeded through matter by a world-soul; salt, sulphur, and mercury were not inert stuffs but principles charged with their own tendencies. Against that whole picture the Cartesian body is a clockwork swept clean of inner powers — no archeus directing the organs, no semina striving toward their forms, only extension, figure, and motion. Mechanism defined itself precisely by emptying nature of the vitalist freight the chemical philosophy had loaded onto it, and the quarrel between the two pictures runs underneath much of the century’s natural philosophy.

The standing difficulty was the seam between the two substances: if mind and body share nothing — if one is thought without extension and the other extension without thought — how does a decision move an arm, or an injury reach the soul as pain? Descartes located the meeting in the brain, naming the pineal gland as the point where the soul’s volitions are translated into motions of the animal spirits, but he left the mechanism obscure. Two things with no common attribute were said to act on each other at a single small place, and no account was given of how. The seam was not a loose end of the system; it was the system’s deepest strain, the place where the very clarity of the division made the union of soul and body inexplicable. His successors inherited the strain rather than the solution.

The occasionalist answer

His successors took the problem and ran. Nicolas Malebranche (1638–1715), the Oratorian priest who turned to Descartes after a chance encounter in 1664 with the posthumous Traité de l’homme, held that mind and body do not interact at all. God alone acts; what are ordinarily called causes are merely occasions upon which God produces the appropriate effect — the doctrine known as occasionalism. The argument was not a pious add-on but a metaphysical claim: a true cause is one between which and its effect the mind perceives a necessary connection, and since no such connection is found between any created things, only God qualifies as a genuine cause. The arm rises not because the will pushes it but because, on the occasion of the willing, God moves it. Malebranche radicalized Descartes rather than repairing him: where Descartes had inconsistently allowed bodies their own forces and the soul its own efficacy, occasionalism withdrew causal power from every creature and lodged it in God, draining the world of secondary causation altogether. He went further still, holding that the mind perceives external things by ideas that exist not in itself but in God — the celebrated vision in God, fusing Augustine’s doctrine of divine illumination with the Cartesian theory of ideas.

Arnold Geulincx (1624–1669), the Antwerp logician dismissed from Leuven and received at Leiden, reached a kindred view independently. He fixed the image that occasionalism is still remembered by: mind and body are two clocks God has wound to keep perfect time, each striking the hour in exact accord with the other though neither moves the other’s works. From the same denial of creaturely power he drew an ethics of humility — ubi nihil vales, ibi nihil velis, where you are worth nothing, there will nothing — that found an unlikely afterlife in the notebooks of Samuel Beckett. Other followers extended the mechanical physics, mapped the laws of motion, or defended the proofs of God against the period’s mounting objections. The school had become a workshop for solving the problem its founder had left open, and occasionalism was the most rigorous of the solutions: it closed the seam by abolishing interaction entirely and paying for it with a God who acts at every instant on every thing.

Spinoza, Leibniz, and the single substance

Two of the century’s largest systems were built in Cartesian terms precisely to heal the split Descartes had opened. Benedictus de Spinoza (1632–1677), whose only signed publication in his lifetime was a geometrical exposition of Descartes’s Principles of Philosophy (1663), inherited the technical vocabulary of substance, attribute, and mode and then collapsed Descartes’s plurality of substances into one. There is, on his account, only a single infinite substance — Deus sive Natura, God or Nature — of which thought and extension are two attributes, two ways the one reality expresses itself. Mind and body are not two things that must somehow be made to interact; they are one and the same mode conceived now under thought, now under extension, so that the order of ideas is the very order of things. The seam vanishes because the two sides were never two. Where Descartes guaranteed the material world by appeal to a God outside it, Spinoza folded God and world into a single necessary order and denied final causes, miracles, and a providential deity altogether — a conclusion the cautious Descartes would have refused, and one for which Spinoza was read for a century as the arch-heretic of the age.

Gottfried Wilhelm Leibniz (1646–1716), who met Malebranche in Paris and engaged occasionalism closely, agreed that created substances do not, in metaphysical strictness, act on one another. But he rejected the occasionalist God who intervenes on every occasion as a perpetual miracle, a divine machinist forever resetting the clocks. In its place he proposed pre-established harmony: God created each substance — each monad — with its whole future folded into it, so that mind and body, like two clocks set going in perfect agreement at the start, run in exact correspondence forever after without any further divine adjustment and without acting on each other at all. The clock image that Geulincx had used to picture occasionalism, Leibniz turned against it: the occasionalist needs a God who keeps correcting the clocks; the harmonist needs only one who made them true. Both men accepted the Cartesian premise that distinct substances cannot genuinely interact, and both built elaborate machinery to live with it. Neither denied the premise; that denial came from a different quarter.

Conway against the divided world

Cartesianism was contested from the first, and not only on technical grounds. In the Dutch universities, where Descartes had lived and written, the conflict broke into the open early: in March 1642 the Calvinist theologian Gisbertus Voetius, rector at Utrecht, secured a formal condemnation of Cartesian philosophy and of its local champion Henricus Regius, on the charge that it overturned Aristotelian orthodoxy and left the young unable to read the schoolmen. The municipal authority banned its teaching. The ban proved a temporary check — within a generation Cartesianism was entrenched across the Dutch faculties — but it marked how dangerous the new philosophy looked to the guardians of the old.

The deeper objection was metaphysical. 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. The Cambridge Platonists — Henry More and Ralph Cudworth foremost — had at first welcomed Descartes as an ally against atheistic materialism, then recoiled: a nature made of dead extension, More came to fear, was a nature from which spirit had been all but banished, and he answered it with a “Spirit of Nature,” Cudworth with a “Plastic Nature,” each an incorporeal formative power threaded through matter to keep the world alive. Their quarrel was with mechanism’s dead matter, drawing on the Neoplatonic inheritance they shared.

Anne Conway (1631–1679), More’s pupil and correspondent at Ragley Hall, pressed the objection furthest. Reading Descartes in More’s translations and Lurianic Kabbalah in the Latin of Knorr von Rosenroth, she argued against both Descartes and Hobbes that spirit and matter are not two kinds of thing but one substance in differing degrees — that body is congealed spirit and spirit refined body, the two shading into each other as light shades into dark, with no inert matter anywhere in the creation, since anything wholly devoid of life would be wholly unlike God and so could not be. This is not a bridge across the Cartesian seam but a refusal of the division that opened it: where Descartes set thinking and extension at an absolute distance and Spinoza made them two attributes of one substance, Conway made them two ends of one living continuum, every creature down to dust possessed of life, motion, and perception. Her Principia philosophiae antiquissimae et recentissimae, written in English, was published in Latin at Amsterdam in 1690 and turned back into English as The Principles of the Most Ancient and Modern Philosophy in 1692. In a single move its title sets her against the Cartesian, the Hobbesian, and the Spinozist systems alike — a vitalist monism that denies the premise the others labored to accommodate.

Scholarship and the texts

The primary Cartesian corpus is largely in the public domain and widely available. Conway’s posthumous treatise survives in the Latin of 1690 and the English back-translation of 1692, the latter among the Library’s holdings. The 1692 English text is freely available in keyed transcription from the Early English Books Online Text Creation Partnership, and the Cambridge Platonism Project hosts a diplomatic edition of the 1690 Latin alongside it. The opposing camp’s anchor text, Cudworth’s The True Intellectual System of the Universe (1678) — with its critique of a “dead cadaverous” Cartesian nature and its doctrine of Plastic Nature — is likewise available in EEBO-TCP transcription at the University of Michigan. Spinoza’s geometrical recasting of Descartes and his own Ethics circulate in R. H. M. Elwes’s nineteenth-century Chief Works and in the Latin Bruder and Van Vloten–Land editions, all long out of copyright.

The modern scholarship treats Cartesianism as a movement rather than a single doctrine. The standard map of the school’s afterlife is set out in the Stanford Encyclopedia of Philosophy’s entries on occasionalism and on Henricus Regius, the latter tracing the Utrecht crisis and the fortunes of Descartes’s first and most wayward Dutch disciple. John Cottingham’s Cambridge Companion to Descartes (1992) and the essays collected around it situate the school’s problems, while Daniel Garber’s Descartes Embodied (2001) reconstructs the physics and the body-as-machine. For the occasionalists, Steven Nadler’s work on Malebranche and the recovery of Arnold Geulincx — whose Ethica appeared posthumously at Leiden in 1675 and was edited with Samuel Beckett’s notes by Han van Ruler, Anthony Uhlmann, and Martin Wilson (Brill, 2006) — have brought the minor figures back into view. Conway’s twentieth-century recovery runs through Marjorie Hope Nicolson, Carolyn Merchant, Allison Coudert, and Sarah Hutton; Hutton’s Anne Conway: A Woman Philosopher (2004) is the standard study.

The seam Descartes left in the brain was the inheritance, not the doctrine. To keep the clean division of thinking and extended substance was to keep the question of how the two could ever meet; to answer that question was, in every case, to alter the division past recognition. The occasionalists kept the two substances and handed all their commerce to God. Leibniz kept them and locked them into a harmony wound at the creation. Spinoza dissolved them into one substance with two faces, and Conway into one living matter graded from dark to light. The mechanical body and the certainty won by doubt could be kept whole; the union of mind and matter could not be held in the same hands that had so sharply cut the two apart. Each system that took up Descartes’s terms found that to make the soul and the world touch again, it had first to unmake the very distinctness on which the whole edifice had been raised.

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

→ Related: Dualism · Neoplatonism · Rene Descartes · Nicolas Malebranche · Anne Conway · Benedictus De Spinoza · Gottfried Wilhelm Leibniz · Isaac Newton · John Locke · Empiricism · Cambridge Platonism · Henry More · Reason · Paracelsianism