Most contemporary philosophers of action accept Aristotle’s view that actions involve movements generated by an internal cause. This is reflected in the wide support enjoyed by the Causal Theory of Action (CTA), according to which actions are bodily movements caused by mental states. Some critics argue that CTA suffers from the Problem of Disappearing Agents (PDA), the complaint that CTA excludes agents because it reduces them to mere passive arenas in which certain events and processes take place. Extant treatments of (...) PDA, most notably those of Michael Bratman and David Velleman, interpret the problem as a challenge to CTA’s ability to capture the role of rational capacities like deliberation and reflection in the etiology of human action. I argue that PDA admits of another interpretation, one that arises when we appreciate that the exercise of higher rational capacities in action presupposes possession of a prior lower-level capacity for basic self-movement – the power to initiate and control one’s bodily behavior. Bolstering CTA so that it accommodates richer exercises of practical thought – as Bratman and Velleman do – will not resolve PDA unless CTA already captures this basic agential power. Adequately responding to PDA, therefore, requires answering a question unaddressed by current responses: How do bodily movements caused by sub-agential items like mental states count as movements actively performed by the whole agent? I argue that CTA can answer this question by adopting a normative account of the nature of self-moving agents. On this view, self-moving agents are teleologically constituted, meaning (1) their nature and proper function derives from their characteristic ends and aims, and (2) the nature and proper function of their parts depend on these ends and aims. Basic self-movement consists of movements caused by a sub-agential part whose own proper function is to generate behavior that constitutes or contributes to the pursuit of the agent’s overall proper function. After showing how this picture applies to artifactual and collective agents (i.e., robots and teams), I extend the account to organic agents (human beings) by sketching a broadly Aristotelian picture of the nature of living things. (shrink)