Justifiable preferences

We characterize preferences over acts that can be represented by a utility function and a multiple–prior, such that an act f is preferred to act g if there is a prior under which the expected utility induced by f is higher than that induced by g. These preferences are referred to as justifiable preferences. We further introduce a generalized model of ambiguity that involves a collection of multiple–priors, namely, multiple multiple–priors and incorporate Bewley’s Knightian model in justifiability: f is preferred to g if, according to at least one set of priors, f is unanimously preferred to g.