In a very broad sense, agency is virtually everywhere. Whenever entities enter into causal relationships, they can be said to act on each other and interact with each other, bringing about changes in each other. In this very broad sense, it is possible to identify agents and agency, and patients and patiency, virtually  everywhere.[1] Usually, though, the term ‘agency’ is used in a much narrower sense to denote the performance of intentional actions. This way of thinking about agency has a long history in philosophy and it can be traced back to Hume and Aristotle, among other historical figures. In contemporary analytic philosophy, it is most commonly associated with the influential work of Anscombe (1957) and Davidson (1963). Anscombe’s and Davidson’s views differ significantly in many respects, but they share the central doctrine that action is to be explained in terms of the intentionality of intentional action. In the debates that followed, the philosophy of action revolved largely around the notion of intentional action. For some time, the term ‘agency’ was rarely used, and if it was, it was usually taken to refer to the exercise of the capacity to perform intentional actions.[2] This has changed in the more recent debate, where talk about agency has become more and more common in many areas of philosophy (and in other areas of research).[3] To some extent, this focus on the notion of agency has been fuelled by a resistance to the assimilation of agency to intentional action. As we will see in the following section, this resistance amounts in some cases to the rejection of the standard conception of action, in some cases it amounts to the rejection of the standard theory of action, and in some it amounts to the more modest claim that there are different kinds of agency.