Descartes’ first love was mathematics, and the core of his metaphysical vision was the mathematicisation of the material world. His first completed work (1618, before his new vision) was a little tract on the mathematics of music, called the Compendium Musicae. There is then a long period of silence as he works on a number of projects:

1. His analytic geometry, which provided a technique for doing geometry without the need for visible diagrams. This was crucial, not only for the future development of mathematics (in particular the calculus), but also for Descartes’ dualism, since it completely separated sensory spatial images with geometrical shapes, from purely intellectual understanding.

2. His general theory about the nature of the material universe: the identification of space with matter; the division of matter into moving particles of three different orders of magnitude; the laws governing the interactions of particles (mechanics); his explanation of planetary motion in terms of vortices in the ether set in motion by the sun; and so on.

3. His theory of light, which is our main source of sensory information about the material world. This involves both the nature of light, and the mathematical laws governing the passage of light from luminous objects to the retina of the eye (how it is reflected by mirrors, and refracted by lenses etc.).

4. His theory of how animal and human bodies function; and in particular how sensory images are formed in the ‘animal spirits’, and how motions in the animal spirits give rise to bodily motions.

5. His theory of the nature of the human soul and of God; of the rational knowledge which distinguishes humans from animals; and of the human passions.

6. His account of the interaction of soul and body (he kept on promising this, but never wrote it).

7. And finally, his explanation of how he succeeded in discovering all this, when no-one had succeeded before — in other words, a new logic of scientific discovery, to replace or complement the syllogistic logic of Aristotle.

The first surviving work was an account of his new logic, called the Regulae ad Directionem Ingenii. It is usually translated as ‘Rules for the Direction of the Mind;’ but ingenium (which I usually translate as ‘wit’) means creative or inventive intelligence, as contrasted with the deductive logic of the intellect or understanding. An anachronistic but more illuminating translation would ‘Rules for Lateral Thinking.’ This work was not printed during Descartes’ lifetime, but it was circulated in multiple manuscript copies. The only manuscript to survive is one which Leibniz bought in Amsterdam in 1670, when he was visiting Spinoza (who wrote a similar work called the Treatise on the Improvement of the Intellect). Descartes wrote the Rules in Latin, in about 1628. The work was first printed in a Dutch translation in 1684, and in the original Latin in 1701 (by the Amsterdam publishers Blaeu, who had published Hobbes’s Latin works in 1668).

For the next few years, Descartes worked at his major treatise on the nature of the material universe, and on the human being. He wrote it in French, and gave it the title The World (Le Monde). He had almost completed it by 1633; but then he learned of Galileo’s condemnation by the Church and imprisonment, for publishing the theory that the earth revolves round the sun (in his Dialogue on the Two Great Systems of the World of 1632). So he decided not to publish it. Most or all of it came out at later dates in one form or another; and only parts of the original version survive. These are The World, or Treatise on Light, and the Treatise on the Human Being, which were published by Clerselier after Descartes’ death.

Go to The World, or Treatise on Light
Go to the Treatise on the Human Being

During the next few years, Descartes wrote up three separate treatises in French, incorporating some material from The World, together with much fresh material. These were the Optics (La Diopotrique), covering his theory of perception, and the mathematics of reflection and refraction; the so-called Meteorology (Les Météores), which is translationese for ‘Astronomy’; and the Geometry (La Géométrie), which contained his new analytic geometry. Having written them, he decided to publish them with a preliminary essay, summarising his new method of reasoning, and setting the treatises in the context of his philosophical system as a whole. The full title of this essay is Discourse on the Right Method for Conducting one’s Reason and Discovering the Truth in the Sciences; and also Optics, Astronomy, and Geometry, which are Examples of this Method. Its approach is autobiographical, and it includes a brief account of Descartes’ method of doubt. Despite the title, there is much less explicit material on method than in the Rules. The four works (Descartes’ first publication) were published together, anonymously, in Holland in 1637. A Latin translation of all but the Geometry was published in 1644, including changes made by Descartes himself. I have translated a short extract from the end of the French version of the Discourse, Part 5.

Go to the Discourse on the Method

Descartes’ decision to publish in French meant that his work would make little impression abroad (French didn’t become the lingua franca of educated Europeans till the end of the seventeenth century). His main readership was educated French men and women, mostly outside university circles. But his ambition was to replace Aristotle as the one great authority in theology, philosophy, and science; so he had to publish in Latin, and in the appropriate style. His first Latin publication was the Meditations on First Philosophy (i.e. metaphysics), which was directed towards university theologians. Descartes himself had been educated at the Jesuit college of La Flèche, and he would have been familiar with the meditational method, set forth by St. Ignatius Loyola, the founder of the Jesuits, in his Spiritual Exercises. The Meditations uses a similar method, and guides the reader through a sequence of thoughts, which they can experience for themselves. Before publication, Descartes had manuscript copies distributed to a number of distinguished philosophers, through the good offices of his friend Marin Mersenne, in Paris. The first edition, of 1641, was published with six sets of objections and Descartes’ replies, and the second edition, of 1642, included a seventh set, and a long letter to Father Dinet. A French translation by Louis-Charles d’Albert, Duc de Luynes, was published in 1647.

Go to Hobbes’s objections to Descartes’ Meditations, and Descartes’ replies

Three year later, in 1644, Descartes published his second and last great Latin work, the Principles of Philosophy. This was designed as a text to be used in university Arts faculties (which was where science was taught at the time). The style is more logical and didactic. The first part covers much the same ground as the Meditations, but more briefly, and most of the rest covers broadly the same ground as the projected The World. The work was incomplete, and it ends with a summary of what he would have said about perception, and the relation between the mind and the body. It was translated into French by the Abbé Claude Picot in 1647, and included a new preface by Descartes, and a number of alterations which may or may not have had Descartes’ approval.

Go to the Principles of Philosophy

Henri de Roy (Henricus Regius), who was Professor of Medicine at the University of Utrecht, was a propagandist for Descartes’ physics, but disagreed with Descartes’ metaphysics. They fell out with each other when Regius published a book which, in Descartes’ view, both plagiarised and distorted some of his as yet unpublished work. In 1647, Regius published a broadsheet listing their points of disagreement, and Descartes immediately responded with his Notes on a certain Broadsheet (Notae in Programma quoddam), published in Latin in 1648.

Go to Notes on a Broadsheet

Descartes then resumed writing in French, focussing on his account of the human being. His Passions of the Soul was published in 1649, just before he died. He failed to complete his Description of the Human Body, which was published by Clerselier in 1664.

Go to the Description of the Human Body

In 1648, a student called Frans Burman managed to track Descartes down in Holland, and interview him about his philosophy. His record of the interview survives, and was first published by Charles Adam in 1896 (reprinted Paris, Vrin, 1975).

Go to Conversation with Burman

To make up for his physical isolation in Holland and elsewhere, Descartes was a prolific correspondent, and large numbers of his letters survive. I have included a few on the mind/body problem.

Go to Correspondence with Princess Elizabeth
Go to Correspondence with Meyssonnier
Go to Correspondence with Mersenne

There are various other minor works which were not published during Descartes’ lifetime, from which I have selected just one extract.

Go to First Thoughts on the Generation of Animals

The standard and virtually complete edition of Descartes’ works is that by Charles Adam and Paul Tannery, Oeuvres de Descartes (Paris, 1897–1910), and a revised edition (Paris, Vrin/CNRS, 1964–76). I have used this edition for all my translations.

There is no complete translation of all Descartes’ writings into English. By far the most complete, accurate, and readable is that by John Cottingham, Robert Stoothoff, and Dugald Murdoch, The Philosophical Writings of Descartes, 2 volumes (Cambridge, 1985). There is a good selection from his correspondence by Anthony Kenny, Descartes, Philosophical Letters (Oxford, 1970).

Go to Index to Descartes texts