A unified theory of counterfactual reasoning

A successful theory of causal reasoning should be able to account for inferences about counterfactual scenarios. Pearl (2000) has developed a formal account of causal reasoning that has been highly influential but that suffers from at least two limitations as an account of counterfactual reasoning: it does not distinguish between counterfactual observations and coun-terfactual interventions, and it does not accommodate back-tracking counterfactuals. We present an extension of Pearl’s account that overcomes both limitations. Our model provides a unified treatment of counterfactual interventions and back-tracking counterfactuals, and we show that it accounts for data collected by Sloman and Lagnado (2005) and Rips (2010). In addition to reasoning about actual states of affairs, hu-mans find it natural to reason about what might have been