Natural revision is contingently-conditionalized revision
This work addresses a theoretical issue in belief revision for AI and logic, but it is incremental as it builds on existing natural revision concepts.
The paper tackles the problem of natural revision being overly conservative by extending it from universal truths to conditionals, based on minimal change and naivety principles, resulting in a revision that restricts changes to current conditions.
Natural revision seems so natural: it changes beliefs as little as possible to incorporate new information. Yet, some counterexamples show it wrong. It is so conservative that it never fully believes. It only believes in the current conditions. This is right in some cases and wrong in others. Which is which? The answer requires extending natural revision from simple formulae expressing universal truths (something holds) to conditionals expressing conditional truth (something holds in certain conditions). The extension is based on the basic principles natural revision follows, identified as minimal change and naivety: change mind as little as possible; believe what not contradicted. The extension says that natural revision restricts changes to the current conditions. A comparison with an unrestricting revision shows what exactly the current conditions are. It is not what currently considered true if it contradicts the new information. It includes something more and more unlikely until the new information is at least possible.