That said, the idea for which he is most often criticized -- his modal realism -- is now making somewhat of a comeback in the form of Tegmark's Level IV multiverse hypothesis.
Isn't modal realism much, much more dramatic a thesis than a mere multiverse? For example, modal realism should entail that there exists a world in which there is no multiverse, even if there is one in our world.
Well, to relate the vocabularies of two theories you need the appropriate translation manual. The manual I'm considering here would equate a "possible world" in Lewis's terminology to a "universe" in Tegmark's terminology. According to Tegmark, all mathematically possible universes are real in some sense, and according to Lewis all metaphysically possible worlds are real in some sense (and Lewis's conception of metaphysical possibility seems pretty close to mathematical possibility). Lewisian worlds are spatio-temporally isolated from o...
Previous Open Thread
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one.
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.