ABSTRACT
Possibility is correlated with what is the case at some world: that there might have been no humans corresponds to the existence of a possible world at which there are no humans. Similarly, necessity is correlated with what is the case at all possible worlds and impossibility with what is the case at none. David Lewis’s realism is a belief in the existence of a vast infinity of possible worlds construed as alternate universes. The different kinds of explanation which Lewis intends in deploying talk of possibilia include conceptual analyses, ontological identifications and a semantic theory. In linguistic realism, the possible worlds are taken as abstract entities- specifically, they are maximal consistent interpreted sentences. Non-realists are those who do not believe in the existence of non-actual possibilia. The most interesting kind of non-realist is he who would, nonetheless, persist in talking as though possible worlds exist and claim to be explaining something in doing so.
