Descartes

Rene Descartes was a French philosopher.

To write his famous Meditations on First Philosophy, Descartes locked himself in a room and thought about existence, arriving at the conclusion that he, as a thinking person, must exist, because even if existence is a delusion, there must be someone to be deluded. However, he was still not sure that the things he perceived exist as well. He used a variant of Anselm's proof of the existence of God to decide that perhaps he wasn't deluded, and perhaps things did exist after all. He thought the soul lived in the pineal gland, and when someone does something, it's just an accident because the brain doesn't control the body, God does. This "god-robot" theory of consciousness got him into ferocious arguments with Hobbes.