French philosophy could be placed and progressively built. Thus he rejected anything which appeared uncertain and decided to only accept apodeictic knowledge as truth. After invoking the possibility of an omnipotent deceiver to reject the external world, the information given to him from his senses, mathematics and logic, Descartes discovered at least one thing could be known apodictically. If he himself was doubting, then he had to exist. Thus Cogito Ergo Sum - I think, therefore I am - became the first principle of Cartesianism. Descartes then claimed that because he discovered the Cogito through perceiving it clearly and distinctly, anything he
Cogito and the History of Madness at the end of the renaissance and the beginning of the classical age. He then discusses the treatment of madness by Descartes in the "Meditations on First Philosophy". Foucault argues that Descartes refuses to recognise a commonality between himself and people who are mad and uses this dissociation as an excuse not to take madness seriously as a grounds for doubt. For Foucault this exclusion of madness by Descartes leads to a cogito that is more or less arbitrarily self-assured of its own rationality. Derrida argues that Descartes might appear to dismiss madness at the point of the meditation to