Uncertainty with Ordinal Likelihood Information

This paper proposes a new framework of choice under uncertainty, where the only information available to the decision maker is about the the ordinal likelihood of the di erent outcomes each action generates. This contrasts both with the classical models where the potential out- comes of each action have an associated probability distribution, and with the more recent complete uncertainty models, where the agent has no information whatever about the probability of the outcomes, even of an ordinal nature. We present an impossibility result in our framework, and some ways to circumvent it that result indiferent ranking rules.