Kant did not take all of the steps down to postmodernism, but he did take the decisive one. Of the five major features of Enlightenment reason—objectivity, competence, autonomy, universality, and being an individual faculty—Kant rejects objectivity. Once reason is so severed from reality, the rest is details—details that are worked out over the next two centuries. By the time we get to the postmodernist account, reason is seen not only as subjective, but also as incompetent, highly contingent, relative, and collective.
