This chapter starts with a discussion of Hume’s regularity theory of causality, which argues that the idea of necessary connection between two events (i.e., cause and effect) cannot be derived from observing the events and must be derived from an internal impression. Simply put, a causal relation is a mere constant conjunction of events. A counterfactual analysis of causation is based on Hume’s remark that if the cause did not occur, the effect would not exist. Lewis develops the analysis using the concept of possible world. In contrast to Hume’s deterministic view of causation, a probabilistic approach argues that causes raise the probability of − but do not necessarily lead to − their effects. Causal graph modeling and vector spacing modeling are two major techniques of identifying causal relations from empirical data, with the latter being more suitable for management research. A mechanism is a causal chain producing the effect of interest, and process tracing is a technique for identifying mechanisms in qualitative research.

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.