Rene Descartes | Biography, Ideas, Philosophy, ‘I Think, Therefore I Am,’ & Facts (2025)

René Descartes (born March 31, 1596, La Haye, Touraine, France—died February 11, 1650, Stockholm, Sweden) was a French mathematician, scientist, and philosopher. Because he was one of the first to abandon Scholastic Aristotelianism, because he formulated the first modern version of mind-body dualism, from which stems the mind-body problem, and because he promoted the development of a new science grounded in observation and experiment, he is generally regarded as the founder of modern philosophy. Applying an original system of methodical doubt, he dismissed apparent knowledge derived from authority, the senses, and reason and erected new epistemic foundations on the basis of the intuition that, when he is thinking, he exists; this he expressed in the dictum “I think, therefore I am” (best known in its Latin formulation, “Cogito, ergo sum,” though originally written in French, “Je pense, donc je suis”). He developed a metaphysical dualism that distinguishes radically between mind, the essence of which is thinking, and matter, the essence of which is extension in three dimensions. Descartes’s metaphysics is rationalist, based on the postulation of innate ideas of mind, matter, and God, but his physics and physiology, based on sensory experience, are mechanistic and empiricist.

Early life and education

Although Descartes’s birthplace, La Haye (now Descartes), France, is in Touraine, his family connections lie south, across the Creuse River in Poitou, where his father, Joachim, owned farms and houses in Châtellerault and Poitiers. Because Joachim was a councillor in the Parlement of Brittany in Rennes, Descartes inherited a modest rank of nobility. Descartes’s mother died when he was one year old. His father remarried in Rennes, leaving him in La Haye to be raised first by his maternal grandmother and then by his great-uncle in Châtellerault. Although the Descartes family was Roman Catholic, the Poitou region was controlled by the Protestant Huguenots, and Châtellerault, a Protestant stronghold, was the site of negotiations over the Edict of Nantes (1598), which gave Protestants freedom of worship in France following the intermittent Wars of Religion between Protestant and Catholic forces in France. Descartes returned to Poitou regularly until 1628.

In 1606 Descartes was sent to the Jesuit college at La Flèche, established in 1604 by Henry IV (reigned 1589–1610). At La Flèche, 1,200 young men were trained for careers in military engineering, the judiciary, and government administration. In addition to classical studies, science, mathematics, and metaphysics—Aristotle was taught from Scholastic commentaries—they studied acting, music, poetry, dancing, riding, and fencing. In 1610 Descartes participated in an imposing ceremony in which the heart of Henry IV, whose assassination that year had destroyed the hope of religious tolerance in France and Germany, was placed in the cathedral at La Flèche.

In 1614 Descartes went to Poitiers, where he took a law degree in 1616. At this time, Huguenot Poitiers was in virtual revolt against the young King Louis XIII (reigned 1610–43). Descartes’s father probably expected him to enter Parlement, but the minimum age for doing so was 27, and Descartes was only 20. In 1618 he went to Breda in the Netherlands, where he spent 15 months as an informal student of mathematics and military architecture in the peacetime army of the Protestant stadtholder, Prince Maurice (ruled 1585–1625). In Breda, Descartes was encouraged in his studies of science and mathematics by the physicist Isaac Beeckman (1588–1637), for whom he wrote the Compendium of Music (written 1618, published 1650), his first surviving work.

Descartes spent the period 1619 to 1628 traveling in northern and southern Europe, where, as he later explained, he studied “the book of the world.” While in Bohemia in 1619, he invented analytic geometry, a method of solving geometric problems algebraically and algebraic problems geometrically. He also devised a universal method of deductive reasoning, based on mathematics, that is applicable to all the sciences. This method, which he later formulated in Discourse on Method (1637) and Rules for the Direction of the Mind (written by 1628 but not published until 1701), consists of four rules: (1) accept nothing as true that is not self-evident, (2) divide problems into their simplest parts, (3) solve problems by proceeding from simple to complex, and (4) recheck the reasoning. These rules are a direct application of mathematical procedures. In addition, Descartes insisted that all key notions and the limits of each problem must be clearly defined.

Descartes also investigated reports of esoteric knowledge, such as the claims of the practitioners of theosophy to be able to command nature. Although disappointed with the followers of the Catalan mystic Ramon Llull (1232/33–1315/16) and the German alchemist Heinrich Cornelius Agrippa von Nettesheim (1486–1535), he was impressed by the German mathematician Johann Faulhaber (1580–1635), a member of the mystical society of the Rosicrucians.

Descartes shared a number of Rosicrucian goals and habits. Like the Rosicrucians, he lived alone and in seclusion, changed his residence often (during his 22 years in the Netherlands, he lived in 18 different places), practiced medicine without charge, attempted to increase human longevity, and took an optimistic view of the capacity of science to improve the human condition. At the end of his life, he left a chest of personal papers (none of which has survived) with a Rosicrucian physician—his close friend Corneille van Hogelande, who handled his affairs in the Netherlands. Despite these affinities, Descartes rejected the Rosicrucians’ magical and mystical beliefs. For him, this period was a time of hope for a revolution in science. The English philosopher Francis Bacon (1561–1626), in Advancement of Learning (1605), had earlier proposed a new science of observation and experiment to replace the traditional Aristotelian science, as Descartes himself did later.

In 1622 Descartes moved to Paris. There he gambled, rode, fenced, and went to the court, concerts, and the theatre. Among his friends were the poets Jean-Louis Guez de Balzac (1597–1654), who dedicated his Le Socrate chrétien (1652; “Christian Socrates”) to Descartes, and Théophile de Viau (1590–1626), who was burned in effigy and imprisoned in 1623 for writing verses mocking religious themes. Descartes also befriended the mathematician Claude Mydorge (1585–1647) and Father Marin Mersenne (1588–1648), a person of universal learning who corresponded with hundreds of scholars, writers, mathematicians, and scientists and who became Descartes’s main contact with the larger intellectual world. During this time Descartes regularly hid from his friends to work, writing treatises, now lost, on fencing and metals. He acquired a considerable reputation long before he published anything.

At a talk in 1628, Descartes denied the alchemist Chandoux’s claim that probabilities are as good as certainties in science and demonstrated his own method for attaining certainty. The Cardinal Pierre de Bérulle (1575–1629)—who had founded the Oratorian teaching congregation in 1611 as a rival to the Jesuits—was present at the talk. Many commentators speculate that Bérulle urged Descartes to write a metaphysics based on the philosophy of St. Augustine as a replacement for Jesuit teaching. Be that as it may, within weeks Descartes left for the Netherlands, which was Protestant, and—taking great precautions to conceal his address—did not return to France for 16 years. Some scholars claim that Descartes adopted Bérulle as director of his conscience, but this is unlikely, given Descartes’s background and beliefs (he came from a Huguenot province, he was not a Catholic enthusiast, he had been accused of being a Rosicrucian, and he advocated religious tolerance and championed the use of reason).