Despite their linchpin role in the ordinary self-understanding of ordinary people, familiar notions of human agency, the central stuff of this chapter, have never succeeded in finding a workable place in the traditional explanatory armamentarium of psychology. Within recent memory, even the slightest whiff of agentiveness was enough to evoke the discipline's signature fear of vitalism (Skinner, 1973), the very thing that psychology as a science had arisen to defeat. While this reflexive aversion to all talk of human agency is perhaps less automatic than was once the case, remnants of this persistent squeamishness are not altogether missing. For many, the problem is set by Wittgenstein's famous question: "What is left over if I subtract the fact that my arm goes up from the fact that I raise my arm?" This curious arithmetic is usually seen to yield two kinds of phenomena. The first, historically ceded to philosophy, has to do with all those human activities that are guided by so-called higher faculties, such as beliefs or intentions. Such purposeful actions, as they are commonly identified, are generally construed as agentive in nature and held in contrast to lesser, nonagentive behaviors. This second