Agreeing to Disagree: A Survey

Working Paper No. 97-18

Posted: 8 Oct 1997

See all articles by Giacomo Bonanno

Giacomo Bonanno

University of California, Davis - Department of Economics

Klaus Nehring

University of California, Davis - Department of Economics

Date Written: June 1997

Abstract

Aumann (1976) put forward a formal definition of common knowledge and used it to prove that two "like minded" individuals cannot "agree to disagree" in the following sense. If they start from a common prior and update the probability of an event E (using Bayes' rule) on the basis of private information, then it cannot be common knowledge between them that individual 1 assigns probability p to E and individual 2 assigns probability q to E with p not equal to q. In other words, if their posteriors of event E are common knowledge then they must coincide. Aumann's Agreement Theorem has given rise to a large literature which we review in this paper. The results are classified according to whether they are probabilistic (Bayesian) or qualitative. Particular attention is paid to the issue of how to interpret the notion of Harsanyi consistency as a (local) property of belief hierarchies.

JEL Classification: C70

Suggested Citation

Bonanno, Giacomo F. and Nehring, Klaus, Agreeing to Disagree: A Survey (June 1997). Working Paper No. 97-18. Available at SSRN: https://ssrn.com/abstract=10812

Giacomo F. Bonanno (Contact Author)

University of California, Davis - Department of Economics ( email )

One Shields Drive
Davis, CA 95616-8578
United States
916-752-1574 (Phone)
916-752-9382 (Fax)

Klaus Nehring

University of California, Davis - Department of Economics ( email )

One Shields Drive
Davis, CA 95616-8578
United States
916-752-3379 (Phone)
916-752-9382 (Fax)

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