Rationalism senses. For instance, his famous dictum, "cogito ergo sum" or "I think, therefore I am", is a conclusion reached "a priori" i.e., prior to any kind of experience on the matter. The simple meaning is that doubting one's existence, in and of itself, proves that an "I" exists to do the thinking. In other words, doubting one's own doubting is absurd. This was, for Descartes, an irrefutable principle upon which to ground all forms of other knowledge. Descartes posited a metaphysical dualism, distinguishing between the substances of the human body (""res extensa"") and the mind or soul (""res cogitans""). This
Cogito and the History of Madness his point of departure for "Cogito and the History of Madness" is Foucault's 1961 book "Folie et déraison". Derrida's paper primarily relies on two sections of Foucault's work, the original 1961 preface in which Foucault makes a number of general comments about the book, setting forth his intentions and methodology, and two and a half pages at the start of the second chapter where Foucault links Descartes to an historical event that silenced madness at the end of the classical age. Foucault's 1961 text was heavily abridged for a popular edition in 1964 that formed the basis for Richard Howard's