I don't know enough about this matter to comment on any detail, but (for some reason; I guess maybe because of the weirdness involved) this thread reminded me of the following discussion:
A while ago, I had a discussion over at the Prosblogion with a poster who defended a probabilistic/collapse interpretation, and held that observers were required for the wave function to collapse. (unfortunately, I can't find a link; the site underwent some changes, and I suspect older posts are gone. That's too bad. It was fun!).
The cat was not a problem for him: it couldn't be dead/alive, because the cat itself was an observer. And so was anything with a brain. Or, for that matter, just a brain.
So, his view was that before the first brains existed, no collapse happened, so the universe existed in some form of different superimposed possibilities or whatever one calls that.
Then, at the first time some brains were possible - even with very low probability - they collapsed the wave function. They were very simple Boltzmann brains, and they weren't very stable. But there were more of those, so wave function collapses kept happening in different ways - but with only Boltzmann brains -, until the first stable brains appear, and from that moment on, Boltzmann brains disappeared (too improbable).
I pointed out that that was more than an interpretation, since all possibilities that contained no brains were excluded, changing the results; for example, in the past, the probability of at least one Boltzmann brain was 1, even in a finite universe. He accepted that, but bit the bullet. He didn't seem to consider that too much of a problem. Also, IIRC, he predicted that in a distant future, the only survivor would see weird things, as she keeps surviving no matter what (unless a Boltzmann brain becomes more probable than her survival. I guess that would usher in a second "Boltzmann Epoch").
Since I don't know much about this, maybe I'm missing something crucial, but tentatively, that seems to raise interesting questions for defenders of the dead/alive cat:
Did wave function collapse happen before there were any observers?
If so, why do we need an observer in the case of he cat (regardless of whether the cat is an observer).
If not, were there human-like Boltzmann brains in the past? (assuming the cat is not an observer; but there are variants for those who believe it is; see above).
If so, that's interesting. But doesn't that alter your probabilistic interpretation, by ruling out possibilities with no brains? (given that the probabilistic interpretation is based on the possible collapsed outcomes apparently, and the possible collapsed outcomes exclude those without brains).
If not, why didn't early Boltzmann brains collapse the huge uncollapsed wave function? What did collapse it in the first place? Or is the past infinite, and there were always brains complex enough to collapse a wave function?
Maybe some other option? (note: "Yahweh collapses the wave function" is not a viable option, of course
).
