revision-vs-update-temporal-distinction

IN premise — summaries/2026/08/24/wiki-Belief_revision.md

Created 2026-08-24T17:11:07+00:00

In AGM belief change theory, 'revision' applies when old beliefs and new information refer to the same situation (agent must discard old beliefs to restore consistency), while 'update' applies when old beliefs refer to the past and new information describes the present (principle of inertia governs).

Summary

When the system learns something new, it has to decide whether it is correcting a mistaken assumption about the current state (revision) or simply observing that the world has changed over time (update). This matters because the two require different handling: revision forces the system to actively resolve contradictions and discard what no longer holds, while update lets it keep everything that is still true and only swap in what has changed, preserving the history of how things got to this point.