SforSingularity comments on Forcing Anthropics: Boltzmann Brains - Less Wrong

17 Post author: Eliezer_Yudkowsky 07 September 2009 07:02PM

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Comment author: SforSingularity 08 September 2009 02:46:15PM *  1 point [-]

In that case, why don't you believe you're a Boltzmann brain?

I think a portion of the confusion comes from implicit assumptions about what constitutes "you", and an implicit semantics for how to manipulate the concept. Suppose that there are N (N large) instances of "you" processes that run on Boltzmann Brains, and M (M << N) that run in sensible copies of the world around me. Which one of them is "you"? If "you" is a particular one of the N that run on Boltzmann Brains, then which one is "you, 10 seconds from now"?

It seems like it ought to be possible to experience a short stream of random sensations; thus in a "Boltzmann Brains Dominate" multiverse, I ought to expect, a priori, that my experiences will be randomness, if I consider myself to be randomly sampled according to the uniform distribution on candidate me's.

Updating on the fact that my experiences this instant are not random noise, if the "Boltzmann Brains Dominate" multiverse is the only hypothesis, I ought to still believe that I am a Boltzmann Brain with very high probability.

But the only copies of "me" that will have a "future" that interacts meaningfully with the decisions I make now are those copies of me that live in the sensible universe, or at least a vaguely sensible universe, where " vaguely sensible" means "acts according to the usual rules of causality for at least long enough for me to get experience back that depends non-trivially upon what decision I took.

So my solution would be to admit that (a) we are not sure exactly what we mean when we use worlds like "me" in a universe/multiverse with lots of copies of the physical correlates of "me", and (b) that our values dictate that even if we conclude with high probability that we are Boltzmann Brains, we ought to condition on the negation of that, because actions outputted to a random environment are pointless.