Why Be Afraid of Identity? - Comments on Sergot and Prakken's Views

The paper discusses the views held by Sergot and Prakken [22] on the import, or non-import, of the identity principle for conditional obligation within a preference-based semantics. This is the principle ©(A/A). The key point is to understand and appreciate what unconditional obligations the principle allows us to detach, and from what premises. It is argued that it does not license the move from A to ©A, which would amount to committing a breach of Hume’s law: no ‘ought’ from ‘is’. It is also shown that the most that is licensed is the move from A to ©A − a move that appears to be harmless, and (above all) compatible with the idea that obligations are essentially violable entities. An existing pragmatic theory can be used to explain it. Objections based on the definition of the unconditional obligation operator are countered.