In short, proper names are rigid designators in models where the possible worlds represent logically alternative states. They need not be rigid designators in models where the possible worlds represent epistemically alternative states. Hesperus and Phosphorus are the same, necessarily so, but we could have used the names “Hesperus” and “Phosphorus” differently without being able to tell we were doing so—a state in which we did this might be epistemically indistinguishable from the actual one. There can be necessary identities that we do not know because necessary truth and known truth do not follow the same rules.