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...

De Finetti's concept of exchangeability provides a way to formalize the intuitive idea of similarity and its role as guide in decision making. His classic representation theorem states that exchangeable expected utility preferences can be expressed in terms of a subjective beliefs on parameters....

We develop a model of undescribable events. Examples of events that are well understood by economic agents but are prohibitively difficult to describe in advance abound in real-life. This notion has also pervaded a substantial amount of economic literature. We put forth a model of such events...

We develop a model of undescribable events. Examples of events that are well understood by economic agents but are prohibitively difficult to describe in advance abound in real-life. This notion has also pervaded a substantial amount of economic literature. We put forth a model of such events...