Journal of Philosophical Logic

, Volume 41, Issue 1, pp 143-172

First online:

Global and Iterated Contraction and Revision: An Exploration of Uniform and Semi-Uniform Approaches

  • Sven Ove HanssonAffiliated withDepartment of Philosophy and the History of Technology, Royal Institute of Technology (KTH) Email author 

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In order to clarify the problems of iterated (global) belief change it is useful to study simple cases, in particular consecutive contractions by sentences that are both logically and epistemically independent. Models in which the selection mechanism is kept constant are much more plausible in this case than what they are in general. One such model, namely uniform specified meet contraction, has the advantage of being closely connected with the AGM model. Its properties seem fairly adequate for the intended type of contraction. However, the revision operator based on it via the Levi identity collapses into an implausible operation that loses all old information when revising by new information. A weaker version, semi-uniform specified meet contraction, avoids the collapse but has the disadvantage of a remarkably weak logic. It is left as an open issue whether there is an intermediate class of contraction operators that yields a more satisfactory logic.


Iterated contraction Iterated revision Specified meet contraction Belief revision Global belief change Global operator