The Unity of Reasons

What are reasons?  Davidson claims that reasons consist of mental states or dispositions; Kenny claims that goals are reasons; Dancy claims that grounds (whether true or false) are reasons; Raz claims that a reason is a fact.  Which of these views, if any, is correct?  Are there different kinds of reasons, e.g. explanatory reasons, motivating reasons, normative reasons, etc.?  Can intentional acts be defined in terms of reasons?  Anscombe writes: "What distinguishes actions which are intentional from those which are not? The answer that I shall suggest is that they are the actions to which a certain sense of the question ‘Why?’ is given application; the sense is of course that in which the answer, if positive, gives a reason for acting.” (Intention, §5)  Raz writes: “The central type of human action is intentional action [...] intentional action is action for a reason.” (Engaging Reason, p.22)  Are these views right?