Re: against UD+ASSA, part 1

From: Wei Dai <weidai.domain.name.hidden>
Date: Wed, 26 Sep 2007 19:15:53 -0700

Hal Finney wrote:
> This is an interesting experiment, but I have two comments. First,
> you could tighten the dilemma by having the mad scientist flip a biased
> coin with say a 70% chance of coming up heads, but then he duplicates
> you if it comes up tails. Now you have it that the different styles of
> reasoning lead to opposite actions, while in the original you might as
> well pick 0 in any case.

In my scenario you're supposed to answer "0" or "non-0" and there are 9 ways
it can be non-zero so in effect it's a 90% biased coin.

> Second, why the proviso that the simulations are identical and
> deterministic? Doesn't the reasoning (and dilemma) go through just as
> strongly if they are allowed to diverge? You will still be faced with a
> conflict where one kind of reasoning says you have your 91% subjective
> probability of it coming up a certain way, while logic would seem to
> suggest you should pick the other one.

The proviso is there because if the simulations are allowed to diverge, what
does the mad scientist do if some of them answer "0" and some answer
"non-0"? I didn't want to deal with that issue.

> But, in the case where your instances diverge, isn't the subjective-
> probability argument very convincing? In particular if we let you run
> for a while after the duplication - minutes, hours or days - there might
> be quite a bit of divergence. If you have 91 different people in one
> case versus 1 in the other, isn't it plausible - in fact, compelling -
> to think that you are in the larger group?

Yes, that's why I said UD+ASSA seems intuitively appealing.

> And again, even so, wouldn't you still want to make your choice on the
> basis of ignoring this subjective probability, and pick the one that
> maximizes the chances for your survivors: as you say, the measure of
> the outcomes that you care about?

Yes. So my point is, even though the subjective probability computed by ASSA
is intuitively appealing, we end up ignoring it, so why bother? We can
always make the right choices by thinking directly about measures of
outcomes and ignoring subjective probabilities.

> If so, then this suggests that the thought experiment is flawed because
> even in a situation where most people would agree that subjective
> perception is strongly skewed, they would still make a choice ignoring
> that fact. And therefore its conclusions would not necessarily apply
> either when dealing with the simpler case of a deterministic and
> synchronous duplication.

I don't understand this part. This thought experiment gives a situation
where the probabilities computed by ASSA is useless, thereby showing that we
need a more general principle of rationality. So I'd say that ASSA is
flawed, not the thought experiment. Or maybe I'm just not getting your
point...
 



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Received on Wed Sep 26 2007 - 22:17:25 PDT

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