Vladimir_Nesov comments on Beauty quips, "I'd shut up and multiply!" - Less Wrong

6 Post author: neq1 07 May 2010 02:34PM

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Comment author: Vladimir_Nesov 07 May 2010 08:52:12PM 2 points [-]

In the sleeping beauty problem, whether the 2/3 or 1/2 is "right" is just a debate about words. The real issue is what kind of many-instance decision algorithm you are running.

Not quite. The question of what do we mean by probability in this case is valid, but probability shouldn't be just about bets. Probability is bound to a specific model of the situation, with sample space, probability measure, and events. The concept of "probability" doesn't just mean "the password you use to win bets to your satisfaction". Of course this depends on your ontological assumptions, but usually we are safe with a "possible worlds" model.

Comment deleted 07 May 2010 10:46:45PM [-]
Comment author: Vladimir_Nesov 07 May 2010 10:56:33PM *  0 points [-]

It is for making decisions, specifically for expressing preference under the expected utility axioms and where uniform distribution is suggested by indifference to moral value of a set of outcomes and absence of prior knowledge about the outcomes. Preference is usually expressed about sets of possible worlds, and I don't see how you can construct a natural sample space out of possible worlds for the answer of 2/3.

Comment deleted 08 May 2010 12:14:48AM [-]
Comment author: Vladimir_Nesov 08 May 2010 12:21:05AM *  0 points [-]

Of course that's the obvious answer, but it also has some problems that don't seem easily redeemable. The sample space has to reflect the outcome of one's actions in the world on which preference is defined, which usually means the set of possible worlds. "Experience-moments" are not carved the right way (not mutually exclusive, can't update on observations, etc.)

Comment deleted 08 May 2010 03:22:00AM [-]
Comment author: Vladimir_Nesov 08 May 2010 10:53:52AM *  0 points [-]

By "can't update" I refer to the problem with marking Thursday "impossible", since you'll encounter Thursday later.

However there is the possibility of subjectively indistinguishable experiences.

It's not a problem with the model of ontology and preference, it's merely specifics of what kinds of observation events are expected.

Experience moments are "mutually exclusive", in the sense that every experience moment can be uniquely identified in theory, and any given agent at any given time is only having one specific observer moment.

If the goal is to identify an event corresponding to observations in the form of a set of possible worlds, and there are different-looking observations that could correspond to the same event (e.g. observed at different time in the same possible world), their difference is pure logical uncertainty. They differ, but only in the same sense as 2+2 and (7-5)*(9-7) differ, where you need but to compute denotation: the agent running on the described model doesn't care about the difference, indeed wants to factor it out.

Comment deleted 08 May 2010 12:42:41PM [-]
Comment author: Vladimir_Nesov 08 May 2010 12:57:19PM 1 point [-]

I humbly apologize for my inability to read (may the Values of Less Wrong be merciful).

Comment deleted 08 May 2010 01:00:53PM *  [-]