It is doubtless too early to assess the break introduced by Michel Foucault, who has been Professor at the College de France (he holds the Chair of the History of Systems of Thought) since 1970, in a philosophic landscape previously dominated by Sartre and by what Sartre called the unsurpassable philosophy of our time, Marxism. From the outset, starting with The History of Madness (1961), Michel Foucault situates himself elsewhere. It is no longer a question of basing philosophy on a new cogito, or of developing a system of things previously hidden from the eyes of the world, but rather of interrogating the enigmatic gesture – a gesture that may be characteristic of Western society – through which true discourses (thus also those of philosophy) are constituted, with their familiar power.

If Foucault is indeed perfectly at home in the philosophical tradition, it is within the critical tradition of Kant, and his undertaking could be called A Critical History of Thought. This is not meant to imply a history of ideas that would be at the same time an analysis of errors that could be measured after the fact, or a deciphering of the misunderstandings to which they are related and on which what we think today might depend. If by thought is meant the act that posits a subject and an object in their various possible relations, a critical history of thought would be an analysis of the conditions under which certain relations between subject and object are formed or modified, to the extent that these relations are constitutive of a possible knowledge.