This essay presents rhetoric as a profound and radical questioning as well as a re-vision of the nature of language itself, and consequently of all aspects of social and cultural life. Based on an elaboration of Nietzsche's thinking on rhetoric, it mainly addresses the rhetorical thinking of four critics - Derrida, Foucault, de Man and Barthes - who, in their common inheritance from and critique of Nietzsche's critical approach, have revealed a dual-nature of rhetoric which in turn sets a dual-task for critical thinking : an endless criticism (demystification) and self-criticism. Critical thinking thus turns out to be a " critique of criticism " and a reflection on the limit of critical thinking itself, i.e., a critique - in the Kantian sense of the word - of the (im)possibility of rational thinking.