The concepts of reasons as supporting elements, of practical reason as a capacity, and of practical reasoning as a process are central in the theory of action. This paper provides a brief account of each. Several kinds of reason for action are distinguished. Practical reason is characterized both as a capacity whose exercise is largely constituted by a kind of responsiveness to reasons and as governed by certain normative principles; and practical reasoning is described as a kind of mental process in which reasons figure as premises and, form those premises, a practical conclusion is drawn. Much of the paper undertakes two related tasks: to distinguish the main kinds of practical reasoning and the associated criteria of assessment and to formulate some important substantive principles of practical reason. These principles yield criteria of several sorts: logical, inferential, epistemic, and material. On the theory presented, although any (non-basic) intentional act can be grounded in practical reasoning, the same acts can be performed for the relevant reason(s) without being so grounded, and in either case their rationality depends on adequate support by the reason(s). One kind of reason is commonly thought to be captured by Kantian hypothetical imperatives. The final sections explore what constitutes a hypothetical imperative and what other principles are needed to account for practical rationality. A major conclusion is that in the domain of practical reason, if there are no categorical imperatives, there are no hypothetical imperatives either.
