P. Chang (1997) put forward an analysis for the power of a cause (as an event) to either generate an effect (another event) in its presence, or prevent the effect in its absence; they are known as "generative cause" and "preventive cause", respectively. Here we invoke signal-detection framework (specifically, the low-threshold and high-threshold versions of SDT) and derive the same formulae given in Chang (1997) for generative and preventive power of a cause. This viewpoint allows a refinement of the notion of causal power, i.e., the power of a generative cause c of an effect e is interpreted as the power of c to cause the occurrence of a sufficient condition for e, and the power of a preventive cause c of e as the power of c to prevent the occurrence of a necessary condition for e. It also follows that generative power and preventive power are two fundamentally independent attributes, quantifying sufficiency and necessity, of an event as a cause for another event in the causal chain. |