A good deal of truth is contained in Richard Rorty’s comment that, in the Middle Ages, God was god; that in the Age of Enlightenment and modernity, reason became god; and that today, in the postmodern age, there is no God. The idol or the god of reason has been shattered. Today, the beloved notion of “rationality”, once one of the most lofty and sacred of terms, conveys little more than a suspect, ambiguous, and modest meaning. Aristotelian reason, Cartesian reason, Kantian reason, Hegelian reason, religious reason, historical reason, dialectical reason, theoretical reason, practical reason, and all the other varieties of reason, have smashed the mirror into a thousand pieces, so as to make it impossible to see any whole and undistorted image reflected in it.
Today when someone speaks of reason, they are referring either to the logical methods of deductive and inductive reasoning, proof and refutation, and so on, or to the products of reason, including philosophy, language, morality, science, and the like. Since these products are all fluid and mutable, it is considered axiomatic in our times that reason changes (or evolves and is infinitely perfectible).
more from Eurozine here.