A long tradition suggests a fundamental distinction between situations of risk, where true objective probabilities are known, and unmeasurable uncertainties where no such probabilities are given. This distinction can be captured in a Bayesian model where uncertainty is represented by the agent's...

This note questions the behavioral content of second-order acts and their use in decision theoretic models. We show that there can be no verification mechanism to determine what the decision maker receives under a second-order act. This impossibility applies even in idealized repeated...

A preference is invariant with respect to a transformation if its ranking of acts is unaffected by a reshuffing of the states under. We show that any invariant preference must be parametric: there is a unique sufficient set of parameters such that the preference ranks acts according to their...