Originally published in 1966, this pivotal work of Mikel Dufrenne revises Kant’s notion of a priori, a concept previously given insufficient attention by philosophers, to realize a rich understanding that finally does justice to one of Kant’s most troubling cruxes. Following the Husserlian analytics of phenomenology, Dufrenne postulates a dualistic conception of the a priori as a structure that expresses itself outside the human subject, but also as a virtual knowledge that points to a philosophy of immediate apprehension or feeling. A friend of Paul Ricoeur, with whom he was detained as a prisoner of war during World War II, Dufrenne’s work until now has been sorely overlooked by American philosophers.