The idea of believing for a good reason has both normative and psychological content. How are these related? Recently, a number of authors have defended a ‘disjunctivist’ view of rationalisation, on which a good reason can make a subject’s responses to it intelligible in a way that mere ‘apparent reasons’ cannot. However, little has been said about the possible epistemological significance of this view or its relationship to more familiar forms of disjunctivism in the philosophy of perception. This paper examines (...) the relationship between epistemological disjunctivism and disjunctivism about rationalisation, arguing that the latter provides an attractive articulation of certain elements of the former. The specific claim is that disjunctivism about rationalisation enables the proponent of epistemological disjunctivism to explain why beliefs that are based on conclusive normative reasons provided by perception are susceptible to a certain kind of undercutting defeat. On the way to motivating this claim, the paper considers possible ways of articulating epistemological disjunctivism in terms of reasons, distinguishes different forms of disjunctivism about reasons for belief and clarifies the relationships between them. (shrink)