David Kellogg Lewis, 1941-2001

When philosophers talk about possible worlds, they’re talking about alternative states of affairs, different ways the world could have been. Possible worlds are tools that help us analyze the meanings of counterfactual statements. But what the heck are these things? What kinds of entities are possible worlds, if they are entities at all? Are they abstract objects? Sets of propositions? Mere fictions that we use as tools for understanding modal claims? Do they exist at all? In his book On the Plurality of Worlds, the late philosopher David Kellogg Lewis argued that possible worlds are real, physically existing worlds just like our own actual world. He dubbed his theory “modal realism.” Needless to say, Lewis’ theory has drawn quite a bit of criticism. Join us as we debate the merits of modal realism while gettin’ drunk on Troegenator Double Bock by Tröegs Independent Brewing!

Abstract:

On our last episode, we discussed the concept of modality, or different ways a sentence can be true. There are two modes of truth. A sentence can be possibly true, in which case it’s true in some possible worlds. Or it can be necessarily true, in which case it’s true in all possible worlds. But what is a possible world? Is it an abstract object? A set of sentences? Or is it something else entirely? It turns out that’s actually a pretty sticky question because most definitions of “possible world” or “modality” rely on the concept of modality itself, meaning they’re ultimately circular. The late philosopher David Lewis claimed he had broken that circle. His solution? If we think of possible worlds as real physically existing objects, then modal statements are no longer modal: they’re now statements about the way things are. You break the circle by dissolving the concept. Lewis’ 1986 book On the Plurality of Worlds was his explanation of his theory, which he dubbed “modal realism.” In it, he explained why his theory is superior to existing theories of modality and defended it against a number of objections.

Reading: On the Plurality of Worlds by David Kellogg Lewis

Download: Episode 5 – On On the Plurality of Worlds

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