steven0461 comments on St. Petersburg Mugging Implies You Have Bounded Utility - Less Wrong

10 Post author: TimFreeman 07 June 2011 03:06PM

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Comment author: RichardKennaway 07 June 2011 03:50:23PM 7 points [-]

Why should I not attach a probability of zero to the claim that you are able to grant unbounded utility?

Let GOD(N) be the claim that you are a god with the power to grant utility at least up to 2**N. Let P(GOD(N)) be the probability I assign to this. This is a nonincreasing function of N, since GOD(N+1) implies GOD(N).

If I assign a probability to GOD(N) of 4**(-N), then the mugging fails. Of course, this implies that I have assigned GOD(infinity), the conjunction of GOD(N) over all N, a probability of zero, popularly supposed to be a sin. But while I can appreciate the reason for not assigning zero to ordinary, finite claims about the world, such as the existence of an invisible dragon in your garage, I do not see a reason to avoid this zero.

If extraordinary claims demand extraordinary evidence, what do infinite claims require?

Comment author: steven0461 07 June 2011 07:37:42PM *  0 points [-]

Even if you do assign zero probability, what makes you think that in this specific case zero times infinity should be thought of as zero?

Comment author: RichardKennaway 07 June 2011 07:47:37PM *  4 points [-]

Because otherwise you get mugged.

You don't literally multiply 0 by infinity, of course, you take the limit of (payoff of N)*probability(you actually get that payoff) as N goes to infinity. If that limit blows up, there's something wrong with either your probabilities or your utilities. Bounding the utility is one approach; bounding the probability is another.