Belief Revision

This chapter first introduces the AGM theory of belief revision. Then it focuses on the problem of iterated belief revisions.

Symbolic and subsymbolic components in the logic of belief change

The intention of this paper is to 'locate' symbolic and subsymbolic components in the theory of belief change. First I will consider the roles of these components within the framework of epistemic logic (Hintikka style) and then apply it on a wider context - i.e. to the theory of belief change (Gärdenfors style or AGM theory). In this way we shall obtain the basis of the logic of belief change.

Strong Syntax Splitting for Iterated Belief Revision

AGM theory is the most influential formal account of belief revision. Nevertheless, there are some issues with the original proposal. In particular, Parikh has pointed out that completely irrelevant information may be affected in AGM revision. To remedy this, he proposed an additional axiom (P) aiming to capture (ir)relevance by a notion of syntax splitting. In this paper we generalize syntax splitting from logical sentences to epistemic states, a step which is necessary to cover iterated revision. The generalization is based on the notion of marginalization of epistemic states. Furthermore, we study epistemic syntax splitting in the context of ordinal conditional functions. Our approach substantially generalizes the semantical treatment of (P) in terms of faithful preorders recently presented by Peppas and colleagues.

On the degeneracy of the full AGM-theory of theory-revision

A general method is provided whereby bizarre revisions of consistent theories with respect to contingent sentences that they refute can be delivered by revision-functions satisfying both the basic and the supplementary postulates of the AGM-theory of theory-revision.