 A belief set over a language \(L\) is a set of sentences that is closed under a given background logic \(\iCn\) (i.e., a theory in the logician’s sense). A belief revision model (BRM) is a pair \(M = \langle \cK, *\rangle\), where \(\cK\) is a set of belief sets over \(L\) and *: \(\cK \times L \to \cK\) is a belief revision function assigning to every belief set \(K\) and every sentence \(A\) a revised belief set \(K*A\). The acceptance condition for conditionals at a belief set in a belief revision model is a straightforward formalization of Ramsey’s test: