Main tenets of modal realism
At the heart of David Lewis's modal realism are six central doctrines about possible worlds:
- Possible worlds exist – they are just as real as our world;
- Possible worlds are the same sort of things as our world – they differ in content, not in kind;
- Possible worlds cannot be reduced to something more basic – they are irreducible entities in their own right.
- Actuality is indexical. When we distinguish our world from other possible worlds by claiming that it alone is actual, we mean only that it is our world.
- Possible worlds are unified by the spatiotemporal interrelations of their parts; every world is spatiotemporally isolated from every other world.
- Possible worlds are causally isolated from each other.