On Donald Turner's theistic multiverse theory (recently ably defended by Klaas Kraay), God, out of his perfect goodness, necessary creates all possible universes that are "good enough", i.e., whose value is above a cut-off line, below which a universe is not worth creating. Thus, the world is a multiverse consisting of infinitely many universes. A God who actualized the best possible world can only create such a multiverse. The metaphysics is similar to that of David Lewis, but with only "good enough" worlds there. This gives a lovely answer to the problem of evil: "Ah, you think this universe would be better without evil E? It sure would—and there is another universe, a better one, in existence that lacks E, but it is better that both this universe and the other one should exist, than that just one of the two should. We see what we would expect to see on the theistic multiverse theory, a world with a lot of evil, but still worth creating."
I want to make a bit of trouble for the notion of a universe worth creating: Whether a universe is worth creating can depend on what other universes, if any, there exist.
Imagine a possible universe U that is just around the cut-off line between good-enough and not-quite-good-enough, and which contains a thousand philosophers who care about little but whether the multiverse hypothesis is correct, and who come to a justified[note 1] belief that there is only one universe concretely in existence. Assuming the notion of a cut-off line makes sense, it seems we could imagine that the universe is so close to the cut-off line that whether the universe falls above the cut-off line or below it depends on whether the philosophers' justified belief that there is only one universe concretely in existence is true. If so, then U is worth creating on its own, since then that belief is true, but it is not worth creating as part of a multiverse, since then that belief is false, and U is so close to the cut-off line that having this belief be wrong pushes it below the cut-off line.
So, the notion of the cut-off line is not so clear: whether a universe is below or above the cut-off line can depend on what other universes there are. Moreover, it seems one can have a pair of universes U1 and U2 such that each is worth creating as part of a multiverse only if the other is not included in the multiverse, and such that neither of the two is better than the other. If we can have such a pair of universes, then there is no unique optimal multiverse. For there will, presumably, be one possible optimal multiverse (i.e., multiverse than which there is no better) that includes U1 but not U2, and another possible optimal multiverse that includes U2 but not U1. How to construct such U1 and U2? Well, again, suppose that the two universes are marginal—very close to the cut-off line—and what decides whether U1 is above it or below it is whether the justified beliefs of U1's philosophers that U2 is non-actual are true, and what decides whether U2 is above it or below it is whether the justified beliefs of U2's philosophers that U1 is non-actual are true.[note 2]
Alex,
ReplyDeleteKlaas' Lewisian proposal has other complications. If there is a single multiverse, then no constituent universe can be spatio-temporally isolated from the others. Lewis allows such quasi-multiverses (sometimes in the temporal form of epochs). If that is true, then Klaas cannot avoid necessitarianism. Whatever happens, necessarily happens. To avoid this Klaas urges that we understand modality along the Lewsian reductivist line. But in order to do that, the worlds in the multiverse must be spatio-temporally isolated. In that case, we have no single multiverse. We have rather lots of distinct possible worlds all of which are on balance good (or good beyond some threshold). But that runs into the same problem Morris had. Why think there are no possible worlds that are very bad? You can use "Anselmian intuitions", but it is clearly question begging against "Non-Anselmain Intuitions". The major problem, in any case, is that he needs worlds to be both isolated and not.
This is probably a little off topic, but, you mention a similarity to Lewis' Modal Realism. Does this Theistic Multiverse view accept counter-part theory as well? Or is it uncommitted to either Counterpart theory or a theory that allows for transworld identity?
ReplyDeleteKlaas wasn't clear on his commitment to counterpart theory, though he did briefly mention Lewisian worries about overlap. I don't think it would matter to his argument whether he accepted it or not. In any case, if you like, you can have modal realism with overlap, too (cf. Kris McDaniel).
ReplyDeleteTurner accepts counterpart theory in his dissertation.
ReplyDeleteThis is weird if you think about the ethical basis. You've got a kind of satisficing going on within each world to determine which worlds are worth creating, and then you've got a kind of maximizing going on determining the moral obligation to produce all the worlds that are good enough. What motivates both satisficing and maximizing at these different levels?
ReplyDeleteIt's maximizing through and through. You maximize value (allegedly) by creating all possible universe that are good enough. Why not just create more copies of the better ones? Because Turner assumes the identity of indiscernibles at least for things that are not spatiotemporally interrelated, so it is impossible for God to create two copies of a universe.
ReplyDeleteBut the very idea of "good enough" is a level of satisficing thrown into the mix. It's not clear what maximizing through and through would look like. It might be realizing all the worlds that achieve the highest level of goodness (which might be one, might be several tied, or might be an empty set). It might be realizing all the worlds whose existence would create more good on average, in which case it's simply maximizing good in the multiverse. But if this notion of "good enough" is some positive greater-than-zero level of goodness, then there's satisficing going on at the level of which worlds count as good enough.
ReplyDeleteI think the idea of the "good enough" is roughly this: a universe is "good enough" if adding it to the multiverse would increase the value of the multiverse (alternative: would not decrease the value of the multiverse?). What that means is going to depend on how one thinks values combine, etc.
ReplyDeleteIt does intuitively seem that if a world has more evil than good, then adding that world to the multiverse would decrease the value of the multiverse, no? (In persona propria I don't know--e.g., I think incommensurability makes such considerations really hard.)
OK, so that's the second option. When I hear "good enough" I think of the third option, which sounds like it has an element of satisficing. The second option does sound like maximizing through and through.
ReplyDeleteAlex, I don't see anywhere in Turner's paper where he assumes Lewsian modal realism or anything close to it. Did you find that in his paper?
ReplyDeleteIf memory serves, Turner (in the piece in the Gale and Pruss anthology) does seem to want to analyze counterfactuals in a Lewisian way, using the island universes in the way Lewis uses worlds.
ReplyDelete