René Descartes

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Article abstract: Descartes’ cardinal contribution is the extension of the mathematical method to all fields of knowledge. He is the father of analytic geometry and the author of the most universally appropriate version of mind-body dualism in the history of philosophy.

Early Life

René Descartes was born to one of the most respected families among the French-speaking nobility in Touraine. His father, Joachim, held the post of counselor to the Parlement de Bordeaux. Descartes’ mother died of tuberculosis only a few days after giving birth to her son, leaving a frail child of chronically poor health to the sole care of his father. René’s physical condition remained delicate until he was in his twenties.

Joachim Descartes was a devoted and admiring father, determined to obtain the best education for “his philosopher.” When Descartes was ten, he was sent to the College of La Flèche, newly established by the Jesuits under the auspices of Henry IV.

Descartes was an exemplary student of the humanities and of mathematics. When, at the age of sixteen, he began his study of natural philosophy, he came to the insight which would later give rise to his revolutionary contributions to modern thought. Uncertainty and obscurity, he discovered, were hallmarks of physics and metaphysics. These disciplines seemed to attract a contradictory morass of opinions that yielded nothing uniform or definite. By contrast, Descartes’ studies in mathematics showed him something firm, solid, and lasting. He was astonished to find that while mathematical solutions had been applied to scientific problems, the method of mathematics had never been extended to important practical matters. At La Flèche, Descartes concluded that he would have to break with the traditions of the schools if he were to find knowledge of any worth.

Descartes left his college without regret, and his father subsequently sent him to Paris. Social life there failed to amuse him, and he formed his most intimate friendships with some of France’s leading scholars and teachers. When he was twenty-one, he joined the army but spent little time campaigning. In his spare time, he wrote a compendium of music and displayed his mathematical genius by instantaneously solving puzzles devised for him by soldiers in his company.

Descartes was housed with a German regiment in winter quarters at Ulm, waiting for active campaign, when the whole core of his subsequent thought suddenly took shape. On the night of November 10, 1619, after a day of intense and agitated reflection, Descartes went to bed and had three dreams. He interpreted these dreams as a divine sign that he was destined to found a unified science based on a new method for the correct management of human reason. Descartes’ sudden illumination and resolve on that night to take himself as the judge of all values and the source of all certainty in knowledge was momentous for the world of ideas.

Life’s Work

Descartes spent the next ten years formulating his method while continuing scientific researches, and occupied himself with travel in order to study what he called “the great book of the world.” He had come to the view that systems of human thought, especially those of the sciences and philosophy, were better framed by one thinker than by many, so that systematizing a body of thought from the books of others was not the best method. Descartes wanted to be disabused of all the prejudices he had acquired from the books of others; thus, he sought to begin anew with his own clear and firm foundation. This view was codified in his first substantial work, Regulae ad Directionem Ingenii (1701; Rules for the...

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Direction of the Mind, 1911). In this work, Descartes set forth the method of rational inquiry he thought requisite for scientific advance, but he advocated its use for the attainment of any sort of knowledge whatever.

Descartes completed a scientific work entitled La Monde in 1633, the same year that Galileo was condemned by the Inquisition. Upon hearing this news, Descartes immediately had his own book suppressed from publication, for it taught the same Copernican cosmology as did Galileo, and made the claim that indicted Galileo’s orthodoxy: that human beings could have knowledge as perfect as that of God. A few years later, Descartes published a compendium of treatises on mathematics and physical sciences which were written for the educated but nonacademic French community; this work obliquely recommended his unorthodox views to the common men of “good sense” from whom Descartes hoped to receive a fair hearing. This work was prefaced by his Discours de la méthode (1637; Discourse on Method, 1649) and contained the Geometry, the Dioptric, and the Meteors.

Discourse on Method provided the finest articulation of what has come to be known as Descartes’ method of doubt. This consisted of four logical rules: first, to admit as true only what was so perfectly clear and distinct that it was indubitable; second, to divide all difficulties into analyzable elements; third, to pass synthetically from what is easy to understand to what is difficult; and fourth, to make such accurate enumerations of the steps of reasoning so as to be certain of having omitted nothing. The method is fundamentally of mathematical inspiration, and it is deductive and analytical rather than experimental. It is a heuristic device for solving complex problems that yields explicit innovation and discovery. Descartes employed his method to this end in the tract on geometry when he discovered a way to resolve the geometric curves into Cartesian coordinates. Such an invention could hardly have come from the traditional Euclidean synthetic-deductive method, which starts from assumed axioms and common notions in order to generate and prove logically entailed propositions.

Descartes’ new method was akin to those found in the writings of Francis Bacon and Galileo, and it was the architectonic of the new science. “Old” science, leftover from ancient and medieval researches, merely observed and classified, and explained its findings in terms of postulated natural purposes of things. The new science inaugurated in the seventeenth century sought, in Descartes’ words, to make men the “masters and possessors of nature.” This goal involved invention and discovery, the generation of new and nonspeculative knowledge, to be put in the service of practical ends. For Descartes and the other seventeenth century “new” scientists, human wonder and understanding were without intrinsic value; what was without practical use or application for mankind, Descartes remarked in Discourse on Method, was absolutely worthless. The new science aimed to create effects, not merely to understand causes.

Descartes intended his method not for mathematics and science only. He envisioned the unity of all knowledge. He employed his method in a purely metaphysical inquiry in Meditationes de Prima Philosophia (1641; Meditations on First Philosophy, 1680) to “establish something firm and lasting in the sciences.” He fashioned in this a primary certainty by rejecting at the outset everything about which it was possible to have the least doubt.

He set aside as false everything learned from or through the senses, and the truths of arithmetic and geometry. Only the proposition, “I think, therefore I am,” remained an indubitable truth. One cannot doubt one’s existence, Descartes reasoned, without existing while one doubts. Thus, cogito ergo sum became his first and most certain principle. Further days of meditation on this principle revealed the certitudes that he was a substance whose whole essence it was to think, entirely independent of his body and of all other material things. His primary truth also enabled him to prove the existence of God.

In this one epochal week of meditations, Descartes made privacy the hallmark of mental activity, moved the locus of certitude to inner mental states, and rejected faith and revelation in favor of clarity and distinctness. Reason itself had previously governed the coherence of what had to be taken as truth; now inner representation, and its correspondence with the external, material world, governed the kingdom of relevant truth. Most philosophers after Descartes have followed his conception of inner representations as the foundation of knowledge of all outer realities. Only in the twentieth century has this position, and its attendant problems, been systematically examined and contested.

The years that followed the publication of Meditations on First Philosophy were marked by controversies resulting from attacks by theologians. Descartes’ orthodoxy was impugned and his arguments were assailed. In 1647, formal objections to the Cartesian metaphysics, along with the author’s replies, were published as a companion volume to a second edition of the Meditations on First Philosophy in French translation.

Descartes’ next project was to be his last. Les Passions de l’âme (1649; The Passions of the Soul, 1650) was a treatise of psychology which explained all mental and physiological phenomena by mechanical processes. This work has striking moral overtones as well. Descartes’ implicit prescription for the best human life is reminiscent of that of the ancient Stoics: Men should strive to conquer their passions in order to attain peace of mind. Descartes maintained in The Passions of the Soul that while people who feel deep passions are capable of the most pleasant life, these passions must be controlled with the intervention of rational guidance. In the end, he claimed that teaching one to be the master of one’s passions was the chief use of wisdom.

In 1649, Descartes responded to the request of Queen Christina of Sweden to join a distinguished circle of scholars she was assembling in Stockholm to instruct her in philosophy. As a result of the Swedish climate and the rigorous schedule demanded by the queen, Descartes caught pneumonia and died the following year.


The thinking of René Descartes epitomizes the transition from the medieval epoch of the Western world to the modern period. Modern man came to deify personal freedom. This tendency originated with the privatization of consciousness and the drive to overcome the rigors of nature. For Descartes, only absolutely certain knowledge counted as wisdom. Descartes envisaged wisdom as having practical benefits for the many, as opposed to being a mere cerebral exaltation for the educated few. Descartes saw the improvement of the mental and physical health of mankind as being the best of these benefits of wisdom. This prospect was ratified by the enterprises of centuries to come.

Descartes was one of the pioneers of modern mathematics. He conceived the possibility of treating problems of geometry by reducing them to algebraic operations and devised the necessary means for making geometric operations correspond to those of arithmetic. He also introduced the notion of deducing solutions from the assumption of the problem’s being solved. This has become such a fundamental technique in algebra and higher mathematics that one can scarcely imagine its having had a genesis. Descartes’ radical distinction between mind and body and his revolutionary method of metaphysical inquiry have had a profound effect on the history of philosophy.


Balz, Albert G. A. Descartes and the Modern Mind. New Haven, Conn.: Yale University Press, 1952. Balz analyzes the pervasive influence of Cartesianism on the last three centuries. The analysis proceeds topically, with exposition of a particular facet of Descartes’ thought and then analysis of its legacy.

Cottingham, John G. Descartes. New York: Basil Blackwell, 1986. Most commentators on Descartes’ philosophy focus on his theory of knowledge; Cottingham takes a broader view of Cartesian philosophy and shows readers a profound Cartesian understanding of human nature. Excellent for beginning students, clear on and faithful to Descartes’ texts.

Gaukroger, Stephen, ed. Descartes: Philosophy, Mathematics, and Physics. Totowa, N.J.: Barnes & Noble Books, 1980. Takes up Descartes’ concern with providing a philosophical foundation for mathematical physics. Ten authors approach this theme from a variety of angles. Extremely well indexed.

Haldane, Elizabeth S. Descartes: His Life and Times. New York: American Scholar Publications, 1966. Artfully crafted, detailed (nearly 400 pages), but eminently readable biography of Descartes. Haldane is especially good at providing historical notes on circumstances which influenced Descartes’ thought and development. Contains a good bibliography of studies of Descartes’ philosophy.

Keeling, S. V. Descartes. New York: Oxford University Press, 1968. One of the best overviews of Descartes’ thought and influence, this book connects Descartes’ development to his thought, gives a systematic reading of his corpus, and critically analyzes the merits and defects of Cartesianism. Well indexed, with a substantial bibliography.

Kenny, Anthony. Descartes: A Study of His Philosophy. New York: Random House, 1968. A standard commentary for beginning students of Descartes’ philosophy which gives particular emphasis to his epistemology. Treats philosophical issues topically in brief, clear chapters. Contains an abbreviated bibliography and a general index.