Life and works of Descartes (1)

René Descartes (1596-1650) came from a family of gentlemen from Touraine. His grandfather, Pierre Descartes, had fought in the wars of religion; his father Joachim, who became an advisor to the Parliament of Brittany in 1586, had three children from his wife, Jeanne Brochard, daughter of the lieutenant general of Poitiers; Fain, Pierre Descartes, succeeded his father, and René was the third. From 1604 to 1612, he was a student at the college of La Flèche, founded by Henri IV and run by the Jesuits. There he received, in the last three years, a teaching of philosophy, consisting of expositions, summaries or commentaries on the works of Aristotle: Organon in the first year, physical books in the second, Metaphysics and the De anima in the third; teaching which, according to tradition, was intended to prepare for theology. In the second year, he also studied mathematics and algebra in the recent treatise of Father Clavius. In 1616, he took his legal exams in Poitiers. Freed by his modest fortune from any material concerns, like many gentlemen of his time, he enlisted in 1618 in Holland, then allied with France against the Spaniards, in the armies of Prince Maurice of Nassau. There he became friends with a doctor of medicine from the University of Caen, Isaac Beeckman, born in 1588, whose diary shows us Descartes dealing with mathematical or physico-mathematical problems with him. In 1619, Descartes, released from his engagement with the Protestant Maurice of Nassau, went to the army that the Catholic Maximilian of Bavaria was gathering against the king of Bohemia, and attended the coronation of Emperor Ferdinand in Frankfurt. It was on November 10, 1619, in a German village near Ulm, that “full of enthusiasm he discovered, he said, the foundations of an admirable science”, an expression which undoubtedly designates a universal method, capable to introduce unity into the sciences. At this time Descartes was going through a period of mystical enthusiasm: he became affiliated, perhaps through the Ulm mathematician Faulhaber, with the Association of the Rosicrucians, which prescribed to its members the free practice of medicine; the titles of the manuscripts of this period, of which only a few lines remain, are significant: the Experimenta, which relate to sensitive things; the Pamassus, the region of the Muses; the Olyrnpica, which relate to divine things; finally, it was around this time that he had a prophetic dream, where he read this verse from Ausonius, in a collection of Latin poets that he practiced as a schoolboy: “Quod vitae sectabov iter? », verse which he interpreted as the sign of his philosophical vocation.

From 1619 to 1628, Descartes travels; from 1623 to 1625, he was in Italy where he made the pilgrimage to Notre-Dame de Loreto where he had vowed to go at the time of his dream; from 1626 to 1628, he stayed in Paris, dealing with mathematics and diopters. It was undoubtedly then that he wrote a pamphlet that remained unfinished, the Regulae ad directionem ingenii, published in 1701 and of which the Logic of Port-Royal (part IV, chàp. II, 1664) translates rules XII and XIII. At this time also, Cardinal de Bérulle, founder of the Oratory, encouraged philosophical research to serve the cause of religion against the libertines.

At the end of 1628, Descartes retired to Holland to seek solitude; except for a trip to France in 1644, he had to stay there, not without changing his stay several times, until 1649. From 1628 to 1629, he wrote a “small treatise on metaphysics” on the existence of God and that of our souls, intended to provide the foundations of its physics. In 1629, he interrupted it to take up physics. It was then that he wrote the Treatise on the World, the progress of which was followed in his correspondence until 1633; his reflections on the phenomenon of parhelia, observed in Rome in 1629, led him to an explanation in order of all the phenomena of nature, formation of planets, gravity, ebb and flow, to arrive at the explanation of man and the human body. Then occurred the event which was to change his plans: Galileo was condemned by the Holy Office for having supported the movement of the earth: “What surprised me so much,” he wrote to Mersenne, “the July 22, 1633, that I almost resolved to burn all my papers, or at least not to let anyone see them. […] I confess that if it [the movement of the earth] is false, all the foundations of my philosophy are also false, because it is demonstrated by them obviously, and it is so linked with all the parts of my treaty that I cannot detach it without returning it. remains all defective.” The treatise remained in Descartes’ papers and was not published until 1677.

However, he does not abandon the idea of making known his physics, and the three essays. Meteora, Dioptrics and Geometry, published in 1637 and preceded by a Discourse on the method, are only intended, in his thinking, “to prepare the way for him and to fathom the ford”. In fact, the Dioptrics, already completed in 1635, contained: on a glass-cutting machine, research continued in 1629; on refraction, a chapter written in 1632; on the vision, the development of the corresponding chapter of the World Treaty. The Meteors were composed in the summer of 1635, and the Geometry, in 1636, while the Meteors were being printed. The original title of the whole work was: “The. project of a universal science which can elevate our nature to its highest degree of perfection. Plus Dioptrics, Meteors and Geometry where the most curious subjects that the author could choose are explained in such a way that even those who have not studied them can understand them”; for which Descartes substitutes: “Discourse on the method for conducting one’s reason well and seeking the truth in the sciences, plus Dioptrics, Meteors and Geometry which are tests of this method.”