November 20 (10:00-11:00) room E.118.2 (main building, 1st floor)
Miklós Pintér (Corvinus University)
Consistent Beliefs without Common Prior
In a strand of the literature, it is assumed that the common prior has full support; that is, every type of every player is assigned positive probability. Morris (1991, 1994) established an epistemological–behavioral duality characterisation of the common prior with full support, showing that a finite type space admits such a prior if and only if it contains no acceptable bet. This result forms the basis of the present paper. The paper makes three contributions: (1) The characterisation of Morris (1991, 1994) is extended to infinite type spaces. (2) The extension is robust: it does not depend on whether the infinite model applies countably additive or purely additive probabilities as beliefs. (3) The analysis implies that the notion of a real common prior—understood as a single probability distribution or a set of probability distributions—is not necessarily meaningful.
The talk is based on joint work with Ziv Hellman (Bar-Ilan University).