Theory and Decision

, Volume 79, Issue 4, pp 547–571 | Cite as

Purely subjective extended Bayesian models with Knightian unambiguity



This paper provides a model of belief representation in which ambiguity and unambiguity are endogenously distinguished in a purely subjective setting where objects of choices are, as usual, maps from states to consequences. Specifically, I first extend the maxmin expected utility theory and get a representation of beliefs such that the probabilistic beliefs over each ambiguous event are represented by a non-degenerate interval, while the ones over each unambiguous event are represented by a number. I then consider a class of the biseparable preferences. Two representation results are achieved and can be used to identify the unambiguity in the context of the biseparable preferences. Finally a subjective definition of ambiguity is suggested. It provides a choice theoretic foundation for the Knightian distinction between ambiguity and unambiguity.


Knightian distinction Maxmin expected utility  Biseparable preference Unambiguous event 

JEL Classification

D80 D81 



I am deeply indebted to David Schmeidler for inspiration, guidance, and support. I am also thankful for Yaron Azieli, Chew Soo Hong, and Ani Guerdjikova for helpful discussion. This research was supported by ANR and Labex.


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Copyright information

© Springer Science+Business Media New York 2015

Authors and Affiliations

  1. 1.LEMMAUniversity of Paris 2ParisFrance

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