Yes, according to Lewis.Lewis' modal realism, to say that some statement R(x) is possible dictates that a possible world exists in which R(x) is not only possible but actually true. This stance is called alethic modality (intimately related to epistemic modality in philosophy of language). Note that Lewis does not claim that for each statement R, a possible world exists in which R holds (consider a world in which R and not R are true at once - such a world cannot exist in an alethic modal sense if we are interested in retaining the Law of Noncontradiction.

Yes, according to Lewis. In Lewis' modal realism, to say that some statement R(x) is possible dictates that a possible world exists in which R(x) is not only possible but actually true. This stance is called alethic modality (intimately related to epistemic modality in philosophy of language). Note that Lewis does not claim that for each statement R, a possible world exists in which R holds (consider a world in which R and not R are true at once - such a world cannot exist in an alethic modal sense if we are interested in retaining the Law of Noncontradiction.