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I noticed an apparently self-defeating aspect of the Boltzmann brain scenario.
Let's say I do find the Boltzmann brain scenario to be likely (specifically, that I find it likely that I myself am a Boltzmann brain), based on my knowledge of the laws of physics. Then my knowledge of the laws of physics is based on the perceptions and memories that I, as a Boltzmann brain, am arbitrarily hallucinating... in which case there is no reason for me to believe that the real universe (that is, whichever one houses the actual physical substrate of my mind) runs on those laws... the very laws that would provide the only evidence that I am indeed a Boltzmann brain.
So supposing that you are a Boltzmann brain is evidence against the possibility of your being a Boltzmann brain (or at least evidence against all of your evidence for it).
I'm still trying to wrap my own brain (Boltzmann or not) around anthropic reasoning, so I'm not sure if I accept the Boltzmann brain argument in the first place (I don't think I do), but this may serve as a specific argument against it.
Has this been discussed before?
Let me see if I can formalize. This might not be quite what you had in mind, but I think it will be similar:
For clarity we can reduce the possible worlds to two, either there are many many more Boltzman brains than human brains (H1) or there are few if any Boltzman brains (H2).
In H2 aprox. everyone who learns of the Boltzman brain hypothesis (and the evidence in favor) is not a Boltzman brain.
In H1 very very few Boltzman brains will learn of the Boltzman brain hypothesis (and the evidence in favor). A significantly larger percentage of the non-Boltzman b... (read more)