What is cartesian doubt?
In the Discorse on Method, Descartes draws a distinction between one side the practical life, a field of action, and the other the science of truth.
In practical life, the resolution must be the watchword. Descartes gives the example of man lost in a forest: if he does not resolve to walk straight, but hesitates and instead keeps coming up on his feet, he has little chance of finding his way. The practical life of merely likely, likely, an ersatz of truth. We must act in the everyday life, without doubt.
In science, because he is seeking the truth, man must achieve absolute truths. These truths can be found only by using a method. Descartes proposes to reject everything he believes to be true, to see if something resists to the doubt.
Methodical doubt and skeptical doubt
Descartes said at the outset that his doubt is to destroy the doubt. It is a method, a question that is provisional. Skeptical doubt, it is permanent. He claims that no truth can be found. Methodical doubt is voluntary and hyperbolic (it has on the body of knowledge). This will escape the absolute doubt and absolute truth. “Confident of our reason” is the starting point of the Cartesian method.
From doubt to Consciousness: I think therefore I am
To doubt, a subject must be an “I”. Even if all are false representations of the subject (example of the candle), it remains that they are those of a subject. There is therefore a matter of right, no doubt thinking. I think an intuitive. Or if I think I am. The cogito is born: the thinker is aware of himself. The subject is not only aware but thinks he thinks.
Consciousness becomes the homeland of the truth, the firm ground on which to base knowledge.
The break with the Greeks (Plato / Socrates / Aristotle) is important: the Greeks believed the truth as transcendent, outside man. Truth existed before man, he could discover through meditation, but not create it. Descartes gives to man his power, the central place of knowledge by saying that truth is immanent.