Cultural Reader: Renè Descartes' Philosophy: Simple Overview and Summary

René descartes (1596–1650), credited with founding modern philosophy, was educated in Jesuit schools in France, beginning with Jesuit college at La Flèche, which was established by the king for the education of the brightest children of the upper classes. In time he came to reject certain principles of his education and developed his Method, the intellectual system expounded in his Discourse on the Method of Rightly Conducting One’s Reason and Seeking Truth in the Sciences(1637). This work was followed by Meditations on First Philosophy (1641), which discuss the “first philosophy”—the nature of God.

For many thinkers Descartes's Discourse on Method represents the beginning of the end of the domination of Aristotle and the Scholastics. The Scholastic philosophers (churchmen teaching throughout Europe) followed Aristotle and St. Thomas Aquinas in a rigid system governed by rules of logic. Although sensory evidence was sometimes relied on, the final authority was the church. Descartes wished on the contrary to substitute the authority of his own reasoning in his investigations into the nature of truth.

His discovery of Method came to him suddenly in 1619 in a “blinding flash” of insight. Seeing the need for a unity of thought in science, he realized that the step-by-step proofs used by geometricians could be employed in all aspects of science. In “Discourse Two” he explains the four rules of his Method and ends with a summary of his insight into geometry:

The first was never to accept anything as true that I did not know to be evidently so: that is to say, carefully to avoid precipitancy and prejudice, and to include in my judgments nothing more than what presented itself so clearly and so distinctly to my mind that I might have no occasion to place it in doubt.

The second, to divide each of the difficulties that I was examining into as many parts as might be possible and necessary in order best to solve it.

The third, to conduct my thoughts in an orderly way, beginning with the simplest objects and the easiest to know, in order to climb gradually, as by degrees, as far as the knowledge of the most complex, and even supposing some order among those objects which do not precede each other naturally.

And the last, everywhere to make such complete enumerations and such general reviews that I would be sure to have omitted nothing.

These long chains of reasonings, quite simple and easy, which geometers are accustomed to using to teach their most difficult demonstrations, had given me cause to imagine that everything which can be encompassed by man’s knowledge is linked in the same way, and that, provided only that one abstains from accepting any for true which is not true, and that one always keeps the right order to one thing to be deduced from that which precedes it, there can be nothing so distant that one does not reach it eventually, or so hidden that one cannot discover it.

Descartes insisted that if each step of the inquiry were free from error, the darkest secrets of nature could be discovered. What he needed once he established this principle was an unassailable position from which to begin. That first point reached, his chain of reasoning could stretch to the stars; without it, true knowledge was impossible. Descartes describes that point in Discourse on Method. It contains the most famous catchphrase in philosophy: “Cogito, ergo sum” (I think, therefore I am). After rejecting many other possible points of departure, Descartes hit upon the statement that was for him unassailable: if he thought about something, then he knew that he must exist, that he was a “thing that thinks,” and that he could not be deceived about the fact that he thought. After establishing this basic truth, he moved toward a proof of the existence of God that did not depend on sensory evidence. It is sometimes described as an intuitive proof, because it depends on a chain of reasoning that starts neither from observation nor from an outside authority.

Descartes' philosophy was influenced by the skepticism of Michel Eyquem de Montaigne(1533–1592), who, in his essays, accepted the view that certainty was impossible because the senses were unreliable and the very existence of the individual unprovable. In the latter part of the sixteenth century, the discovery of important classical texts—especially Sextus Empiricus’s translation of the work of the ancient Greek philosopher Pyrrho—was enormously influential in Europe because they cast doubt on all things. The fracturing of the Christian Church into several sects called into question the most authoritative truths of all, most notably when Martin Luther challenged the authority of the church on the question of the truth. Doubt and uncertainty were therefore part of a crisis in European thought. Descartes worked out his theories a hundred years after Luther, and with the publication of Discourse on Method he seemed to have begun to offer a way out of the crisis.

Ironically, Descartes’ philosophical reliance on intuitive chains of reasoning did not work in his favor in scientific investigations of the kind we now rely on. He was uncomfortable with evidence gathered by the senses—what is now calledempirical evidence—and therefore made little contribution to the development of modern science. However, he did not hold science back. He especially admired Galileo (1564–1642), the most renowned scientist of his time.

Another legacy of Descartes is the body-mind split. He states in his Fourth Meditation that he is aware of the distinctions between his body and his mind and sees them as different in certain essentials. Eventually, he postulates that the mind’s existence may not depend on the body. Such a view was widely developed in poetry and literature and is for some critics a lamentable fact.