Abstract

When David Lewis (1986) told us that possible worlds were a ‘paradise for philosophers,’ he neglected to add that they are a minefield for decision theorists. Possibilities—be they nomological, metaphysical, or epistemic possibilities—have little to do with subjective probabilities, and it is these latter that matter most to decision theory. Bernard Katz and Doris Olin (2007) have tried to solve the two-envelope problem by appealing to possible worlds and counterfactual conditionals. In this paper I explain why any such attempt is misguided, and why we, qua decision theorists, must focus on the probable rather than the possible.