This chapter assesses the merits of Aquinas’s hylomorphic account of the human act by comparing it to three contemporary action theories: (1) Donald Davidson’s causal theory of action, (2) Jennifer Hornsby’s agent-causal account, and (3) John Searle’s component analysis. It argues that Aquinas’s account has several advantages over these theories. First, it does not fall prey to the problem of deviant causal chains, which besets Davidson’s theory. Nor does it fall victim to the problem of the disappearing agent, which besets Davidson’s as well as Searle’s theory. Finally, Aquinas’s theory also has an advantage over Hornsby’s account. On Hornsby’s picture, a bodily human act is a causing that occurs inside the body, which has the counterintuitive consequence that human acts are unobservable, on her view. The chapter argues that for Aquinas only one component of a bodily human act is unobservable, namely, the volition, while the bodily commanded act is open to our gaze. Despite these advantages, it argues that Aquinas’s theory also has a drawback, namely, the dualism on which it is predicated. But it suggests that his hylomorphic theory of the human act can be detached from his dualism.

In this chapter, I articulate and defend several views that play important roles throughout the remainder of the book. First, I articulate the task of a metaphysical theory of action as that of providing an account of the distinction between actions and mere behaviours. I then distinguish two things we might mean to talk about when we talk about someone’s actions: the things they do; and their particular doings of those things. I argue that we are ontologically committed to entities of both types, and defend my preferred ontology, according to which particular doings are events, while the things we do are a kind of property we possess.

In this chapter, I introduce the topic of negative action. I provide a rough account of the distinction between positive and negative actions, of the distinction between two commonly-discussed kinds of negative behaviour (omitting and refraining), and of what distinguishes negative actions from mere failures to do something. Then, drawing on this discussion and the discussion of Chapter 1, I articulate the problem of negative action: negative actions seem to be genuine actions; actions seem to be events; but (at least some) negative actions seem to be, not events, but absences thereof. I trace the widespread acceptance of the latter claim to Deflationism, the view – often held only implicitly – that negative action sentences express negative existentials.

In this chapter, I consider whether we can solve the problem of negative action by insisting that intentional omissions, refrainments, and the like aren’t really actions at all, but ‘mere manifestations of agency’. I argue that the distinction between actions and mere manifestations of agency is more difficult to draw than it may appear, and that drawing such a distinction requires us to abandon plausible claims about the relations between powers and their manifestations, and between intentional behaviour and practical reasons. We must find some other solution to the problem.