Untangling the Epidemiologist's Potential Outcomes Approach to Causation

In this paper I untangle a recent debate in the philosophy of epidemiology, focusing in particular on the Potential Outcomes Approach to causation. As the POA strategy includes the quantification of ‘contrary-to-fact’ outcomes, it is unsurprising that it has been likened to the counterfactual analysis of causation briefly proposed by David Hume, and later developed by David Lewis. However, I contend that this has led to much confusion. Miguel Hernan and Sarah Taubman have recently argued that meaningful causal inferences cannot be drawn from obesity. This paper prompted Alex Broadbent to criticise the POA conception of causation, accusing two of the four theses its proponents are committed to, of circularity and falsity. Here I scrutinise Broadbent’s claims, and suggest that a Popperian approach to causal inference in epidemiology diffuses both of his objections. However, I move on to argue that the POA’s commitment to granting only manipulable conditions causal-status, renders the position implausible as a conceptual analysis of causation. That said, I conclude that the strategy the POA employs is an effective tool for effect-measurement in intervention-cases; if it is a conceptual analysis of causation at all, it must be restricted to the causal analysis of manipulable conditions. The POA’s failure to successfully demarcate causal from non-causal conditions simpliciter should therefore not be viewed as a serious threat.