Will the Multiverse hypothesis yield enough universes that it satisfies David Lewis’ notion of extreme modal realism, which states that for every logically possible world, there is an actual world to which it corresponds? I have already heard (and rehearsed) the objection that if one believes in libertarian free will then there are some logically possible worlds which are possibly not included in the infinitely many universes which exist, such as a world in which I freely choose to pretend I’m dying during a final exam. However, this is not likely to be thought compelling to somebody who either rejects, or else at least is apprehensive about accepting, libertarian free will. However, here’s another way to demonstrate that the Multiverse would not actualize all logically possible worlds: it is logically possible that the Copernican principle be false (and even falsified). The Copernican principle basically says that we occupy no special or a-typical corner of the universe, such that the laws and regularities which we observe to hold here are the same laws and regularities which we would observe anywhere in the universe. However, the Multiverse hypothesis assumes tacitly that universes have fixed physical laws – initial constants and quantities which are fixed for that universe. It is, however, logically possible for some worlds to fail to fit the description of ‘copernican’ worlds, at which the physical laws are fixed and ‘universal‘.
Therefore, the Multiverse hypothesis will not get you all the way to extreme modal realism.