Benquo 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: Benquo 07 June 2011 10:27:20PM *  2 points [-]

Utility doesn't have to take infinity as an argument in order to be infinite. It just has to have a finite output that can be summed over possible outcomes. In other words, if Sum(p X U(a) + (1-p) X U(^a)) is a valid expression of expected utility, then by induction, Sum X U(i)) should also be a valid expression for any finite n. When you take the limit as n->infinity you run into the problem of no finite expectation, but an arbitrarily large finite sum (which you can get with a stopping rule) ought to be able to establish the same point.

I still don't understand 3b. TimFreeman wasn't postulating an acausal universe, just one in which there are things we weren't expecting.

Comment author: handoflixue 08 June 2011 03:45:05AM 0 points [-]

magfrump seems to have nailed it. I find it interesting how controversial that one has been :)

For infinite sums, basically, if the sum is infinite, then any finite probability gives it infinite expected utility (infinity * [1/N] = infinity). If both the sum and probability are finite, then one can argue the details (N * [1/N^2] < 1). The math is different between an arbitrarily large finite and an infinite. Or, at least, I've always assumed Pascal's Wager relied on that, because otherwise I don't see how it produces an infinite expected utility regardless of scepticism.

Comment author: Benquo 08 June 2011 04:20:29AM 0 points [-]

If the utility can be arbitrarily large depending on N, then an arbitrarily large finite skepticism discount can be overcome by considering a sufficiently large N.

Of course a skepticism discount factor that scales with N might be enough to obviate Pascal's Wager.