A trichotomy of attitudes for decision-making under complete ignorance

We study decision criteria under complete ignorance, that is, when there is no available information regarding plausible probability distributions over the possible outcomes. We characterize the set of criteria satisfying quasi-transitivity, Savage's independence, duplication, a strong version of dominance and scale invariance. Only three criteria satisfy these requirements. These criteria are the well-known protective criterion, its dual criterion which we call hazardous, and a neutral criterion which is the composition of both (a decision is strictly preferred according to this criterion to another one if both the protective and the hazardous criteria strictly prefer the former). (C) 2009 Elsevier B.V. All rights reserved.