The "Possibility of Practical Reason" explores the foundational questions of moral psychology: How can any of our behaviour qualify as acting for a reason? How can any considerations qualify as reasons for us to act? David Velleman argues that both possibilities depend on there being a constitutive aim of action - something that makes for success in action as such, in the same way that truth makes for success in belief. Considerations qualify as reasons for acting by virtue of their relevance to the constitutive aim; and our behavior qualifies as acting for a reason when it responds to such considerations in pursuit of the aim. The eleven papers that make up this book (two of them previously unpublished) discuss such topics as the relation between value and practical reasoning, the foundations of decision theory, freedom of the will, shared intention, and the motivational role of the imagination.