obligation—especially if it seems to you, after reflection, that the teaching in question comes from God himself. But what about rationality and warrant? And since rationality is included in warrant, we can simplify: what about warrant? The part of Calvin’s definition of faith that is especially striking to contemporary ears is that on his account faith is a really special case of knowledge (“a sure and certain knowledge”; see also the account of true faith in the Heidelberg Catechism, above, p.