René Descartes, Latinized name Renatus Cartesius (1596 – 1650) was a French philosopher, mathematician, and scientist who invented analytical geometry, linking the previously separate fields of geometry and algebra. One of the most notable intellectual figures of the Dutch Golden Age, René Descartes is also widely regarded as one of the founders of modern philosophy. René Descartes has often been called the father of modern philosophy, and is largely seen as responsible for the increased attention given to epistemology in the 17th century. He laid the foundation for 17th-century continental rationalism, later advocated by Spinoza and Leibniz, and was later opposed by the empiricist school of thought consisting of Thomas Hobbes, John Locke, George Berkeley, and David Hume.
René Descartes saw very clearly that all truths were linked with one another, so that finding a fundamental truth and proceeding with logic would open the way to all science. Descartes discovered this basic truth: "I think, therefore I am."
Refusing to accept the authority of previous
philosophers, Descartes frequently set his views apart from the philosophers who
preceded him. In the opening section of the Passions of the Soul, an early
modern treatise on emotions, Descartes goes so far as to assert that he will
write on this topic "as if no one had written on these matters before." His best
known philosophical statement is "cogito, ergo sum" ("I think, therefore I am";
French: Je pense, donc je suis), found in Discourse on the Method (1637; in
French and Latin) and Principles of Philosophy (1644, in Latin).
Descartes's Meditations on First Philosophy (1641) continues to be a standard text at most university philosophy departments. Descartes's influence in mathematics is equally apparent; the Cartesian coordinate system was named after him. He is credited as the father of analytical geometry, the bridge between algebra and geometry—used in the discovery of infinitesimal calculus and analysis. Descartes was also one of the key figures in the Scientific Revolution.
In Meditations on First Philosophy, Descartes attempted to demonstrate the existence of God and the distinction between the human soul and the body. Humans are a union of mind and body; thus Descartes's dualism embraced the idea that mind and body are distinct but closely joined. While many contemporary readers of Descartes found the distinction between mind and body difficult to grasp, he thought it was entirely straightforward. Descartes employed the concept of modes, which are the ways in which substances exist.
In Discourse on the Method, Descartes recalls: I
entirely abandoned the study of letters. Resolving to seek no knowledge other
than that of which could be found in myself or else in the great book of the
world, I spent the rest of my youth traveling, visiting courts and armies,
mixing with people of diverse temperaments and ranks, gathering various
experiences, testing myself in the situations which fortune offered me, and at
all times reflecting upon whatever came my way to derive some profit from it.
Unlike many moralists of the time, Descartes did not deprecate the passions but rather defended them; he wept upon Francine's death in 1640. According to a recent biography by Jason Porterfield, "Descartes said that he did not believe that one must refrain from tears to prove oneself a man." - Porterfield, J., René Descartes (New York: Rosen Publishing, 2018).
Descartes concludes that he can be certain that he exists because he thinks. But in what form? He perceives his body through the use of the senses; however, these have previously been unreliable. So Descartes determines that the only indubitable knowledge is that he is a thinking thing. Thinking is what he does, and his power must come from his essence. Descartes defines "thought" (cogitatio) as "what happens in me such that I am immediately conscious of it, insofar as I am conscious of it". Thinking is thus every activity of a person of which the person is immediately conscious. - Descartes, René (1644). The Principles of Philosophy. IX.