ABSTRACT
It is very natural to think that what exists is just what actually exists. Of course, there might have been flying pigs, fire-breathing dragons, golden mountains, perpetual-motion machines and so on. But such things do not exist. They might have, but they don’t. David Lewis disagrees. What might have existed, does exist – in some other possible world. Possible worlds exist too, in just the way that the actual world does. This is the infamous doctrine of modal realism. Lewis writes:
I advocate a thesis of plurality of worlds, or modal realism, which holds that our world is one world among others. There are countless other worlds, other very inclusive things. . . . They are isolated: there are no spatiotemporal relations at all between different things that belong to different worlds. Nor does anything that happens at one world cause anything to happen at another. . . . The other worlds are of a kind with this world of ours. . . . Nor does this world differ from others in its manner of existing. . . . The worlds are not of our own making.2
