Epistemic entrenchment and possibilistic logic

摘要

This note points out the close relationships existing between recent proposals in the theory of belief revision made by Gardenförs based on the notion of epistemic entrenchment, and possibility theory applied to automated reasoning under uncertainty. It is claimed that the only numerical counterparts of epistemic entrenchment relations are so-called necessity measures that are dual to possibility measures, and are also mathematically equivalent to consonant belief functions in the sense of Shafer. Relationships between Spohn's ordinal conditional functions and possibility theory are also laid bare.