Reasons can play a variety of roles in a variety of contexts. For instance, reasons can motivate and guide us in our actions (and omissions), in the sense that we often act in the light of reasons. And reasons can be grounds for beliefs, desires and emotions and can be used to evaluate, and sometimes to justify, all these. In addition, reasons are used in explanations: both in explanations of human actions, beliefs, desires, emotions, etc., and in explanations of a (...) wide range of phenomena involving all sorts of animate and inanimate substances. This diversity has encouraged the thought that the term 'reason' is ambiguous or has different senses in different contexts. Moreover, this view often goes hand in hand with the claim that reasons of these different kinds belong to different ontological categories: to facts (or something similar) in the case of normative/justifying reasons, and to mental states in the case of motivating/explanatory reasons. In this paper I shall explore some of the main roles that reasons play and, on that basis, I shall offer a classification of kinds of reasons. As will become clear, my classification of reasons is at odds with much of the literature in several respects: first, because of my views about how we should understand the claim that reasons are classified into different kinds; second, because of the kinds into which I think reasons should be classified; and, finally, because of the consequences I think this view has for the ontology of reasons. (shrink)