Pascal's mugging

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Revision as of 03:56, 4 November 2009 by Eliezer Yudkowsky (talk | contribs) (the problem isn't the unbounded utility function, it's how fast the utilities grow)
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Pascal's mugging refers to a thought experiment in decision theory, a finite analogue of Pascal's wager. The situation is dramatized by a mugger:

Now suppose someone comes to me and says, "Give me five dollars, or I'll use my magic powers from outside the Matrix to run a Turing machine that simulates and kills 3^^^^3 people."

If an agent's utilities over outcomes can potentially grow much faster than the probability of those outcomes diminishes, then it will be dominated by tiny probabilities of hugely important outcomes. As pointed out by Peter de Blanc, its expected utilities may not even converge. The prior over computable universes in Solomonoff induction seems to have this problem in particular - more generally, if prior probability goes as simplicity of physical law, then small increases in complexity can correspond to enormous increases in the size of even a finite universe.

Intuitively, one is not inclined to acquiesce to the mugger's demands - or even pay all that much attention one way or another - but what kind of prior does this imply?

Blog posts

See also


  • Nick Bostrom (2009). "Pascal's Mugging". Analysis 69 (3): 443-445.  (PDF)