PFIA 2024
JIAF
Minimal Change in Modal Logic S5
Carlos Aguilera-Ventura, Jonathan Ben-naim, Andreas Herzig
We study belief revision for the modal logic S5. We introduce rationality postulates and design a semantics that is based on the Hamming distance and that satisfies all postulates. We demonstrate the usefulness of our operator by revisiting a major criticism of AGM revision operations, namely that the revisions of ‘p and q’ and ‘p and p implies q’ are identical. We show that the problem disappears if instead of material implication we use the modal operator 1 of strict implication that can be defined in S5.