Cogito, ergo sum
Doubting itself proves the doubter exists. This first certainty resists all doubt, and philosophy henceforth begins from the subject.
The Early Modern Age · 1596 – 1650
René Descartes
笛卡尔
Father of modern philosophy, who found 'I think, therefore I am' through universal doubt, split mind from matter, and invented analytic geometry.
RationalismBirthplace: La Haye, Touraine
I think, therefore I am.
Source: Discourse on Method, part 4
Descartes was born to minor nobility in central France, lost his mother in infancy, and as a sickly boy at the Jesuit college of La Flèche was allowed to sleep until noon, a habit he kept for life. He studied law, then resolved to learn from 'the great book of the world' and joined armies in Holland and Germany. On the night of 10 November 1619, in a stove-heated room on the Danube, he had three dreams and concluded that his mission was to found a unified science.
He lived in seclusion in Holland for twenty years, moving often to avoid interruption. News of Galileo's trial in 1633 made him suppress The World. In 1637 he published in French the Discourse on Method with three essays, one of which, the Geometry, fused algebra with geometry; coordinate systems are still called Cartesian. The Meditations on First Philosophy appeared in 1641 with objections from Hobbes, Gassendi, Arnauld and others and his replies.
The Meditations begin by doubting everything: the senses deceive, I may be dreaming, a demon may be systematically deceiving me. But as long as I doubt I think, and as long as I think I exist. From that fixed point he proves God's existence, lets God's veracity guarantee that clear and distinct ideas are true, and rebuilds the external world. Mind is thinking substance and matter extended substance, wholly different, and animals are mere machines. In 1649 Queen Christina of Sweden summoned him to Stockholm and demanded lessons at five in the morning; he survived one winter and died of pneumonia.
Key Ideas
Methodical doubt
Treat everything doubtful as false for the time being and see what remains. Doubt is not the goal but a tool for clearing the ground.
Mind–body dualism
The essence of mind is thought and of matter extension; they are distinct substances. How they interact became the problem of the next three centuries.
Clear and distinct ideas
Whatever I perceive clearly and distinctly is true. The criterion of truth moves from authority to the self-evidence of reason.
Mechanical nature
The material world, including animal bodies, is a machine running by laws of motion. Final causes are expelled from natural science.
Influenced by
Influenced
- Thomas Hobbes
- Blaise Pascal
- Baruch Spinoza
- John Locke
- Nicolas Malebranche
- Gottfried Wilhelm Leibniz
- George Berkeley
- Immanuel Kant
- Edmund Husserl
The Cartesian Meditations call phenomenology a 'neo-Cartesianism': it too begins by suspending everything, but what remains is not a thinking substance but the whole structure of consciousness.
- Jean-Paul Sartre
- Emmanuel Levinas
The idea of the infinite in Descartes' Third Meditation was the text he prized most: a finite mind containing an idea that exceeds it is the very structure of the Other's entry into the self.
- Maurice Merleau-Ponty
The adversary of the Phenomenology of Perception is Descartes' cogito: before the reflective 'I think' there is an 'I can', the body's perceptual hold on the world.
- Simone de Beauvoir
- Thomas Nagel
He defended Descartes' intuition: the subjective character of consciousness is what every objective description leaves out, and even if dualism is wrong it grasps a real problem.