For David Lewis's Modal Realism, do the worlds and individuals that inhabit them exist necessarily? In a sense, the answer is "no". For an individual to exist necessarily would be for it to have a counterpart at every world, but Lewis is pretty explicit that this isn't required for counterpart theory or for modal realism.
But, this is where the question gets tricky, in order for the analysis of modality in terms of possibilia to go through it would seem that possibilia would need to exist necessarily. This is because it is generally thought that a successful analysis of a concept should hold necessarily, and if there were no possible worlds or individuals the analysis would break down.
Hence, my question, does the modal realist need "there are possible worlds and individuals that inhabit them" to be a necessary truth, even if he doesn't require any particular possible individuals to necessarily exist?