TimFreeman comments on A summary of Savage's foundations for probability and utility. - Less Wrong

34 Post author: Sniffnoy 22 May 2011 07:56PM

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Comment author: endoself 24 May 2011 05:19:16PM 2 points [-]

Constructing a St. Petersburg lottery relies on this, but I don't see why that means "unbounded utility" depends on it

If there are only a finite number of options, utility can only be unbounded if at least one of the options has the possibility of utilities with arbitrarily large absolute value. It is hard to deal with an infinite number of options, but it might be possible depending on how that works with the other axioms, but this is irrelevant because P6 was not connected to the proof of bounded utility.

unbounded utility isn't even a consequence of these axioms, indeed the opposite is so.

That is why I was initially concerned about P6.

to get real numbers you need an Archimedean assumption of some sort.

I don't think real numbers are the best field to use for utility because of Pascal's mugging, some of the stuff described here, and this paper.

Comment author: TimFreeman 24 May 2011 05:41:27PM 0 points [-]

I don't think real numbers are the best field to use for utility because of Pascal's mugging

Are we agreed that bounded real-valued (or rational-valued) utility gets rid of Pascal's mugging?

Comment author: endoself 24 May 2011 07:17:57PM 3 points [-]

Yes. Bounded utility solves tons of problems, it just doesn't, AFAICT, describe my preferences.

Comment author: Eliezer_Yudkowsky 24 May 2011 08:59:52PM 0 points [-]

The bound would also have to be substantially less than 3^^^^3.

Comment author: TimFreeman 24 May 2011 09:20:51PM 2 points [-]

The bound would also have to be substantially less than 3^^^^3.

As you know, if there is a bound, without loss of generality we can say all utilities go from 0 to 1.

Repairing your claim to take that into account, if you're being mugged for $5, and the plausibility of the mugger's claim is 1/X where X is large, and the utility the mugger promises you is about 1, then you get mugged if your utility for $5 is less than 1/X, roughly. So I agree that there are utility functions that would result in the mugging, but they don't appear especially simple or especially consistent with observed human behavior, so the mugging doesn't seem likely.

Now, if the programming language used to compute the prior on the utility functions has a special instruction that loads 3^^^^3 into an accumulator with one byte, maybe the mugging will look likely. I don't see any way around that.