Lyotard on Kant

"The reader of Kant cannot fail to wonder how the critical thinker could ever establish conditions of thought that are a priori. With what instruments can he formulate the conditions of legitimacy of judgments when he is not yet supposed to have any at his disposal? How, in short, can he judge properly 'before' knowing what judging properly is, and in order to know what it might be?"

J-F. Lyotard, Lessons on the Analytic of the Sublime, translation Elizabeth Rottenberg, Stanford University Press, 1994, 32.