How Many Are Affected? A Real Limit of Epidemiology

We read with interest Charlie Poole’s commentary [1] on our paper, “Redundant causation from a sufficient cause perspective,”[2] in which he questions the utility of the sufficient component cause (SCC) model for examining differences between etiologic and excess effects. Poole contends that the concept we term “redundant causation” is uncomplicated and (we presume), well understood. He questions whether “it needs to be explained in terms any deeper than those of potential outcomes” [1]. His critique of our paper focuses on our hypothetical and simplistic example of sufficient causes (SCs) of liver cancer. To be of value, Poole believes our example must be realistic and must bring “aspects of the potential outcome and sufficient cause models, and their interface, into sharp relief” [1]. His concerns raise larger issues about the roles of simplifications and the SCC model in methods research in general. We address each of these below.