It has occurred to me that there is a kind of fine-tuning of multiverse theories.
If there is too large a variety of universes within a multiverse, we get skeptical problems. For instance, if all possible laws of nature are realized, then induction-friendly laws like “Gravity is always attractive” are either outnumbered by or at least do not outnumber nasty laws like “Gravity is attractive until the end of March 2026 and repulsive afterwards”. Or if there are too many kinds of material arrangements, we would expect scenarios with local order, like Boltzmann brains to outnumber or at least not be outnumbered by scenarios like brains arising by evolution.
On the other hand, if there are too few universes, then the laws by which universes are generated need to be themselves fine-tuned or else there won’t be life.
So, a multiverse theory needs to be tuned as to the variety of universes it supposes. I don’t have a a great argument that this tuning is highly improbable, but it might be. My intuition says, for what it’s worth, that the on naturalism we should either expect a single universe or a very wide and varied multiverse, and the latter is likely to engender skepticism.
2 comments:
Is there any appeal of multiverse theory other than its power to undermine fine tuning arguments for intelligent design? Does it have any scientific validity? Would it have arisen without the challenge of ID?
There are theories, like string theory, in physics that naturally give rise to a multiverse, and so these multiverses have an appeal apart from finetuning. As far as I know, none of these theories are yet confirmed scientifically.
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