Full Idea
In early work Foucault writes in opposition to the Enlightenment. ..The reason that was supposed to liberate us has itself become the primary instrument of our domination. ..His heroisation of the mad aims to set up an alternative to the regime of reason.
Gist of Idea
Foucault originally felt that liberating reason had become an instrument of domination
Source
report of Michel Foucault (works [1978]) by Gary Gutting - Foucault: a very short introduction 7
Book Reference
Gutting,Gary: 'Foucault' [OUP 2005], p.76
A Reaction
Adorno and Horkheimer are cited as background. I hear Spinoza turning in his grave, because right reason could never be an instrument of domination.