This is a book about why we do what we do. It’s also about how we arrive at an understanding of other people’s actions. A traditional view in philosophy—‘common-sense psychology’ (CP)—holds that representational mental states (paradigmatically, beliefs and desires) lie at the heart of intentional action and social cognition. According to this view, intentional actions are responses to mental states which capture a person’s reasons for action: I open the cookie jar because I’d like a cookie and believe there is one in there. As a corollary, understanding someone else’s action is often held to depend on attributing them plausible mental states and reasoning: I think you opened the cookie jar because you wanted a cookie and believed there was one in there. However, this approach has been thrown into doubt by experimental findings which apparently show that CP’s appeal to reasons and reasoning is overly demanding and overly intellectualizing, painting an idealized picture of decision-making which is rarely borne out by the evidence. If we get out of our armchairs and examine how people actually make decisions, the claim is, what we find is that people don’t do what they do, typically, based on the reasons they have, nor do people understand one another’s actions via attributing them beliefs and desires and rational processing involving those kinds of states. In short, what we find is that CP is wrong. This book is an attempt to reject that line of argument and to defend the common-sense perspective.