On the (Alleged) Plurality of Worlds

David Lewis was a brilliant philosopher. But his case for concrete possible worlds never quite added up.

Last Sunday, I wrote about the multiverse and briefly touched on its purely philosophical equivalent—David Lewis’s theory of concretely existing possible worlds. Today, I want to say a little bit more about why I disagree with Lewis.

Lewis, remember, thinks that what it means to say that such-and-such isn’t but could have been true is that there’s at lea…