What is rational agency? What conceptual tools should we use when reasoning about it? What are the best methods for discovering the springs of our action and justifying our theoretical claims about it? A good starting point is to look at our common-sense, pre-analytical discourse about human action. There are two forms of such discourse. Firstly there is a descriptive discourse, describing what we do and explaining why we are doing it. When we are asked “Why did you do that?” we normally say “Because I wanted to and believed that by acting in this way I would achieve that result.” That is, we name a want and belief. These together constitute our reason for acting. “Why did you do that?” always expects a reason in response, and only accepts ...