I mean, if I start out as part of a group of 2^10 people, and that group is subjected to an iterative process whereby we split the group randomly into equal subgroups A and B and kill group B, then at every point along the way I ought to expect to have a history of being sorted into group A if I'm alive, but I ought not expect to be alive very long. This doesn't seem to depend in any useful way on the definition of "alive."
I agree with all that. I don't quite see where that thought experiment fits into the discussion here. I see that the situation where we have survived that iterative process is analogous to fine-tuning with MWI, and I agree that fine-tuning is unsurprising given MWI. I further claim that fine-tuning is unsurprising even in a non-quantum universe. Let me describe the though experiment I have in mind:
Imagine a universe with very different physics. (1) Suppose the universe, by nature, splits into many worlds shortly after the beginning of time, each with different physical constants, only one of which allows for life. The inhabitants of that one world ought not to be surprised at the fine-tuning they observe. This is analogous to fine-tuning with MWI.
(2) Now suppose the universe consists of many worlds at its inception, and these other worlds can be observed only with great difficulty. Then the inhabitants still ought not to be surprised by fine-tuning.
(3) Now suppose the universe consists of many worlds from its inception, but they are completely inaccessible, and their existence can only be inferred from the simplest scientific model of the universe. The inhabitants still ought not to be surprised by fine-tuning.
(4) Now suppose the simplest scientific model describes only one world, but the physical constants are free parameters. You can easily construct a parameterless model that says "a separate world exists for every choice of parameters somehow", but whether this means that those other worlds "exist" is a fruitless debate. The inhabitants still ought not to be surprised by fine-tuning. This is what I mean when I say that fine-tuning is not surprising even without MWI.
In cases (1)-(4), the inhabitants can make an anthropic argument: "If the physical constants were different, we wouldn't be here to wonder about them. We shouldn't be surprised that they allow us to exist." Does that makes sense?
Ah, I see.
Yes, I agree: as long as there's some mechanism for the relevant physical constants to vary over time, anthropic arguments for the "fined-tuned" nature of those constants can apply; anthropic arguments don't let us select among such mechanisms.
Thanks for clarifying.
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