We analyze the preference aggregation problem without the assumption that individuals and society have fully determined and observable preferences. More precisely, we endow individuals and society with sets of possible von Neumann–Morgenstern utility functions over lotteries. We generalize the...

We provide a generalization of Harsanyi's (1955) aggregation theorem to the case of incomplete preferences at the individual and social level. Individuals and society have possibly incomplete expected utility preferences that are represented by sets of expected utility functions. Under Pareto...

Decision makers sometimes have to choose between alternative options about which they have no preference: either they judge the options equally valuable (indifference) or they have no judgment about their relative value (noncomparability). Choosing randomly is generally considered a natural way...

We provide possibility results on the aggregation of beliefs and tastes for Monotone, Bernoullian and Archimedian preferences of Cerreia-Vioglio, Ghirardato, Maccheroni, Marinacci, and Siniscalchi (2011). We propose a new axiom, Unambiguous Pareto Dominance, which requires that if the...