David Lewis writes,
I advocate a thesis of plurality of worlds, or modal realism, which holds that our world is but one world among many. There are countless other worlds, other very inclusive things. Our world consists of us and all our surroundings, however remote in time and space; just as it is one big thing having lesser things as parts, so likewise do other worlds have lesser otherworldly things as parts... The worlds are many and varied. There are enough of them to afford worlds where (roughly speaking) I finish on schedule, or I write on behalf of impossibilia, or I do not exist, or there are no people at all, or the physical constants do not permit life, or totally different laws govern the doings of alien particulars with alien properties. There are so many other worlds, in fact, that absolutely every way that a world could possibly be is a way that some world is.
Many philosophers meet Lewis’ view with an “incredulous stare”; how could anyone believe in something which we have no access? Explain Lewis’ justification for believing in modal realism.