Belief change as change in epistemic entrenchment

In this paper, it is argued that both the belief state and its input should be represented as epistemic entrenchment (EE) relations. A belief revision operation is constructed that updates a given EE relation to a new one in light of an evidential EE relation, and an axiomatic characterization of this operation is given. Unlike most belief revision operations, the one developed here can handle both multiple belief revision and iterated belief revision.The authors are thankful to John G. Bennett, Henry E. Kyburg, Jr., Norman Foo, Pavlos Pepas, Maurizio Pagnucco, Bob Hadley, members of the Knowledge Systems Group at the University of Sydney and participants of the AI'93 workshop on Belief Revision: Bridging the Gap Between Theory and Practice at Melbourne where a version of this paper was presented, for their suggestions. The authors also express their gratitude to the two anonymous referees for Synthese for their excellent comments and suggestions. Of course it is only the authors that are responsible for the errors that remain.