Aumann has shown that agents who have a common prior cannot have common knowledge of their posteriors for event $E$ if these posteriors do not coincide. But given an event $E$, can the agents have posteriors with a common prior such that it is common knowledge that the posteriors for $E$...

Aumann has shown that agents who have a common prior cannot have common knowledge of their posteriors for event $E$ if these posteriors do not coincide. But given an event $E$, can the agents have posteriors with a common prior such that it is common knowledge that the posteriors for $E$...

Given the regularity condition on posteriors proposed in Lehrer and Samet (2011), we show that Lehrer and Sametʼs (2011) characterization of agreeing to agree in countable-information models cannot be extended to uncountable-information models. This answers an open question raised in Lehrer and...

This chapter is a very compressed review of the neoclassical orthodoxy on the nature of rationality on economic theory. It defends the orthodoxy both against the behavioral criticism that it assumes too much and the revisionist view that it assumes too little. In places, especially on the...

To answer the question in the title we vary agentsʼ beliefs against the background of a fixed knowledge space, that is, a state space with a partition for each agent. Beliefs are the posterior probabilities of agents, which we call type profiles. We then ask what is the topological size of the...

We generalize the ``No-speculative-trade" theorem for finite unawareness belief structures in Heifetz, Meier, and Schipper (2013) to the infinite case.

We define a generalized state-space model with interactive unawareness and probabilistic beliefs. Such models are desirable for potential applications of asymmetric unawareness. We compare unawareness with probability zero belief. Applying our unawareness belief structures, we show that the...

We define a generalized state-space model with interactive unawareness and probabilistic beliefs. Such models are desirable for many potential applications of asymmetric unawareness. We develop Bayesian games with unawareness, define equilibrium, and prove existence. We show how equilibria are...

The paper provides a speci?cation of belief systems for models of large economies with anonymity in which aggregate states depend only on cross-section distributions of types. For belief systems satisfying certain conditions of mutual absolute continuity, the paper gives a necessary and...