In his essay ‘The Order of the Discourse’, Michel Foucault offers an outline of the character and focus of his future research. He proposes to identify the processes by which in our society discourse is ‘at once controlled, selected, organised, and redistributed by a certain number of procedures whose role it is to ward off its powers, to gain mastery over its chance events, to evade its ponderous, formidable materiality’. To this end, Foucault isolates three ‘principles of exclusion’. They are prohibition, the division between reason and madness and the rejection of the latter, and thirdly, the opposition between true and false.

According to Foucault, the third principle of exclusion finds its origin in the classical rejection of the sophist and the Platonic foundation of a ‘will to truth’ or ‘will to knowledge’.