Tribute to Jean-Yves Jaffray by the French Group of Decision Theory

We show that when decision makers are of the multiple prior kind, there is an equivalence between no betting and non empty intersection of the sets of priors.

We show that the monotone continuity condition introduced by Arrow (1970) is the behavioral counterpart of countable additivity and weak compactness of the set of priors in a maxmin expected utility model. This generalizes Arrow's original result, who considered the special case of a singleton...