Rene Descartes (1596-1650) was a French philosopher. In Latin his name is Renatus Cartesius, from which we get the word “Cartesian.” He moved Western philosophy beyond Aristotle, created analytic geometry by applying algebra to geometry and was a leading light of the new science.
Descartes is the one who said “Cogito, ergo sum”, Latin for “I think, therefore I am”.
Descartes said that if you really want to know the truth, then at least once in your life you must doubt everything. From this universal doubt he knew that he existed because he doubted! “I think, therefore I am.” From there he proved that God exists, using the proofs of Anselm and Aquinas. But God would not deceive us, therefore we can trust our senses too. And so on.
Descartes reasoned from truths he could not doubt to new truths and then reasoned from these new truths to derive yet other truths and so on through a process of deduction.
Descartes did to philosophy what Euclid had done to geometry, building it from the ground up. So had Aristotle, but Descartes was far more thorough. It was quite unlike Bacon’s science by induction.
Descartes founded the school of rationalism. It said that man’s knowledge is based on reason and certain inborn ideas. This was later opposed by the empiricism of Locke.
Descartes saw the body and all of nature as matter in motion, as moving parts working together. The human mind, on the other hand, was something completely different. The mind was not material, it was not an ordinary part of nature. You could not see it or touch it. We only know about minds because we all experience them.
This is known as mind/body dualism, where the world is divided into mind and body. Most philosophers in the English-speaking world see it as a false distinction.
Descartes wondered where the mind was connected to the body. So he cut open dead animals and he cut open dead men and looked. Only man had a pineal gland, so he thought that was it. Years later, however, the pineal gland was found in other animals.
Descartes was a pious Catholic and, like Galileo, saw himself as helping the Church into the new age of thought. The Church did not see it that way.
While Descartes was writing his master work on science, “Le Monde”, the Church condemned Galileo for teaching the theory of Copernicus as true. That is just what Descartes had done in “Le Monde”! He stopped writing the book and never put it out. Instead he came up with his theory of vortices. It had some following till Newton proved Copernicus right once and for all.
In 1649 he went to Sweden to teach philosophy to the queen. The cold was too much for him and he died of pneumonia a year later.
His best books:
- Discourse on Method (1637)
- Meditationes de prima philosophia (1641)
- Principia philosophiae (1644)