Abstract

A simple argument against Lewisian modal realism as portrayed in On the Plurality of World arises from its treatment of doxastic modalities. It is easily shown that if it is true, it is impossible to doubt the theory on ontological grounds, or, that, if it is possible to maintain doubt about modal realism’s existential postulate, it has to be false. The argument hinges on the fact that modal realism’s main ontological hypothesis, if true, is necessarily true