David Deutsch: belief

Transcript context

…How do your views relate to the philosophical modal realism of David Lewis? There are interesting parallels. As a physicist, I’m interested in what the laws of physics tell us is so, rather than in philosophical reasoning about things, unless they impinge on a problem that I have. So yes, I’m interested in, for example, the continuity of the self — whether, if there’s another version of me a very large number of light-years away in an infinite universe, and it’s identical, is that really me? Are there two of me, one of me? I don’t entirely know the answer to that. It’s why I don’t entirely know the answer to whether I would go in a Star Trek transporter. The modal realism certainly involves a lot of things that I don’t think exist — at least, not physically. I’m open to the idea that nonphysical things do exist: like the natural numbers, I think, exist. There’s a difference between the second even prime, which doesn’t exist, and the infinite number of prime numbers, which I think do exist. I think that there is more than one mode of existence, but the theory that all modes of existence are equally real — I see no point in that. The overlap between Everett and David Lewis is, I think, more coincidental than illuminating. If the universe is infinite and if David Lewis is correct, should I feel closer to the David Lewis copies of me? The copies or near copies of me in this universe? Or the near copies of me in the multiverse? It seems very crowded all of a sudden. Something whose purpose was to be economical doesn’t feel that way to me by the end of the metaphysics.…

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