René Descartes

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René Descartes (Latinized Cartesius, 1596–1650) was a French philosopher and mathematician whose redescription of nature as matter in motion did much to end the world-picture that Renaissance magic and hermeticism had assumed. He is remembered for the method of systematic doubt, for the single certainty he claimed to reach through it — cogito, ergo sum, I think, therefore I am — and for splitting the world into two kinds of stuff: mind, which thinks, and body, which is sheer extension and obeys mechanical law.

That division is the part of his work that bears on esoteric history. The inherited cosmos of the magi was alive throughout: stars with influences, herbs with virtues, hidden correspondences binding the human being to the heavens, a soul of the world running through all of it. Descartes drained that animacy from physical nature. In his account, body is dead extension, fully explicable as machinery, with mind walled off on the other side; the planets push, they do not signify. He did not refute astrology or alchemy so much as leave them no room to stand. Scholarship has long treated this — together with the parallel work of Bacon and Galileo — as a turning point after which the magical sciences slowly lost their standing as knowledge, however long they went on being practised.

The irony, much noted, is how close his own beginnings ran to that older world. As a young man travelling in Germany during the opening of the Thirty Years’ War, in the winter of 1619, he is reported to have shut himself in a heated room and, on a single night in November, dreamed three vivid dreams that he took as a sign of his vocation — the founding scene of his philosophy, by his own later telling. The same years saw the Rosicrucian manifestos circulating through the German lands, and Descartes is said to have tried to find the unseen Brotherhood that issued them, without success. From this his earliest biographer, Adrien Baillet, recorded the suspicion that Descartes was himself a Rosicrucian, and reported the joke offered against it: that he could not be one of the Invisibles, since he was plainly visible to all.

How much weight any of this carries is contested. The dreams are attested only at second hand, through a lost notebook Baillet paraphrased; the Rosicrucian contact is rumour worked up by his enemies and by later occult writers as much as by historians. What the episode marks is real enough — that the man who helped build the mechanical universe came up through the same ferment of hermetic and Rosicrucian hope as the figures his philosophy displaced, and emerged from it pointed the other way.

His mature thought set the terms for a century of argument. Spinoza pressed his dualism toward a single substance; Malebranche read mind and body as joined only by God; the mind-body problem he bequeathed is still open. Within Western esotericism his name tends to stand for the loss it laments — the moment a cosmos full of meaning was reconceived as a mechanism, and the soul left with nowhere in the physical world to belong.

→ Related: Francis Bacon · Galileo Galilei · Benedictus De Spinoza · Nicolas Malebranche · Blaise Pascal