It is commonplace that belief in possible worlds not only burdens one with a large ontology, but with metaphysical problems about their existence and identity conditions and epistemological problems about justifying belief in them. In this paper, we challenge these commonplaces, and show that belief in possible worlds doesn’t burden necessarily one with large ontology, nor with the mentioned metaphysical and epistemological problems. We argue specifically for the claim that the most fundamental existence principle of world theory is not only true in small models, but is derivable from analytically true principles. If this is true, it puts the lie to the commonplace view that a commitment to possible worlds entails a commitment to a large ontology. Moreover, the particular theory we use to support our claims precisely addresses the metaphysical problems about the existence and identity of worlds and offers a solution of the epistemological problem of justifying our belief in worlds.