Belief revision: A critique

Nir Friedman*, Joseph Y. Halpern

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


We examine carefully the rationale underlying the approaches to belief change taken in the literature, and highlight what we view as methodological problems. We argue that to study belief change carefully, we must be quite explicit about the "ontology" or scenario underlying the belief change process. This is something that has been missing in previous work, with its focus on postulates. Our analysis shows that we must pay particular attention to two issues that have often been taken for granted: the first is how we model the agent's epistemic state. (Do we use a set of beliefs, or a richer structure, such as an ordering on worlds? And if we use a set of beliefs, in what language are these beliefs are expressed?) We show that even postulates that have been called "beyond controversy" are unreasonable when the agent's beliefs include beliefs about her own epistemic state as well as the external world. The second is the status of observations. (Are observations known to be true, or just believed? In the latter case, how firm is the belief?) Issues regarding the status of observations arise particularly when we consider iterated belief revision, and we must confront the possibility of revising by φ and then by ¬φ.

Original languageAmerican English
Pages (from-to)401-420
Number of pages20
JournalJournal of Logic, Language and Information
Issue number4
StatePublished - 1999

Bibliographical note

Funding Information:
★ Some of this work was done while both authors were at the IBM Almaden Research Center. The first author was also at Stanford while much of the work was done. IBM and Stanford’s support are gratefully acknowledged. This work was also supported in part by NSF under grants IRI-95-03109 and IRI-96-25901, by the Air Force Office of Scientific Research under grant F49620-96-1-0323, and by an IBM Graduate Fellowship to the first author. A preliminary version of this paper appeared in L.C. Aiello, J. Doyle, and S.C. Shapiro, eds., Principles of Knowledge Representation and Reasoning: Proceedings Fifth International Conference (KR ’96), pp. 421–431, 1996.


  • Agm postulates
  • Belief revision
  • Iterated revision


Dive into the research topics of 'Belief revision: A critique'. Together they form a unique fingerprint.

Cite this