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From: Nick Bostrom <bostrom.domain.name.hidden>

Date: Sat, 28 Feb 1998 11:45:08 +0000

Wei Dai wrote:

*> The problem is that nothing a person does can affect the outside view,
*

*> which is static.
*

Only on the AUH, right?

*> > There might be many instances of the experimenter after the
*

*> > experiment. Whose satisfaction are you talking about? If you are
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*> > talking about average satisfaction among the actual instances of the
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*> > experimenter that will exist after the experiement, and all you care
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*> > about is this average (you don't care at all about how many instances
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*> > are enjoying this satisfaction) then you might indeed get the
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*> > implication that you should play Russian roulette in your thought
*

*> > example, but what's so paradoxical about that? It wouldn't mean that
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*> > I would have any reason to play Russian roulette in that situation,
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*> > for I don't think I have the goals that your argument presupposes. I
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*> > care about how many branches I will continue to exist on/how many
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*> > copies there will be of me.
*

*>
*

*> These things are part of the outside view. They will remain the
*

*> same no matter what you do, so how does it make sense to have a goal of
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*> changing them?
*

Isn't it the case that on the AUH, *everything* remains the same no

matter what I do?

In one sense, yes; in another sense, no. I think it's the same as

with any other physical theory.

The sense in which I *can* make a difference,on the AUH, is I think

the following: If I choose to do action X, then that indicates that X

is a rather probable thing to happen (it has a big measure, even

though in some universes I will not do X in a similar situation). It

might not matter whether we say that I "cause" X to have a big

measure by wanting it, or we say that the ground why I want X is

that the event of me bringing X about by wanting it has a relatively

big measure.

*> > That's how you define the probability, yes, but how do you define the
*

*> > proposition "I will perceive X."?
*

*>
*

*> I don't know how to define it directly, but its meaning is implicit in the
*

*> definition of the probability.
*

It looks to me now as if your definition of this probability agrees

with the (second) one I suggested (and which you say that Tegmark

also uses), except that I assumed a finite number of discrete

universes, whereas you stated the definition in terms of measures.

*> > But your argument, it seems, presupposes that I can't care about how
*

*> > many instances there will exist of me. That seems wrong.
*

*>
*

*> Part of my argument is that it doesn't make sense to have goals that refer
*

*> to the outside view because the outside view is fixed. But I also showed
*

*> (with the first paradox) that Tegmark's definition of probability is not
*

*> self-consistent. I think that is the more serious problem, since if we
*

*> have a consistent definition of probability that isn't compatible with our
*

*> current version of decision theory, we can always modify decision theory
*

*> or change our ideas of what is rational.
*

I've just reread your post about the first paradox and will comment

on it later.

*> > Well I think that's problematic. How do we interpret these
*

*> > "measures"? I.e. what does it mean to say that a certain instance of
*

*> > experience has a certain measure m?
*

*>
*

*> One possible interpretation is that every string has an infinite number of
*

*> instances, but some have relatively more instances than others. This is
*

*> somewhat analagous to intervals of real numbers between 0 and 1. There are
*

*> an infinite number of real numbers in every such interval, but some
*

*> intervals have relatively more real numbers than others.
*

Some intervals may have a greater measure, but surely they have

equally many real numbers in them. That follows from the fact that R

is a dense order-type.

_____________________________________________________

Nick Bostrom

Department of Philosophy, Logic and Scientific Method

London School of Economics

n.bostrom.domain.name.hidden

http://www.hedweb.com/nickb

Received on Sat Feb 28 1998 - 03:49:35 PST

Date: Sat, 28 Feb 1998 11:45:08 +0000

Wei Dai wrote:

Only on the AUH, right?

Isn't it the case that on the AUH, *everything* remains the same no

matter what I do?

In one sense, yes; in another sense, no. I think it's the same as

with any other physical theory.

The sense in which I *can* make a difference,on the AUH, is I think

the following: If I choose to do action X, then that indicates that X

is a rather probable thing to happen (it has a big measure, even

though in some universes I will not do X in a similar situation). It

might not matter whether we say that I "cause" X to have a big

measure by wanting it, or we say that the ground why I want X is

that the event of me bringing X about by wanting it has a relatively

big measure.

It looks to me now as if your definition of this probability agrees

with the (second) one I suggested (and which you say that Tegmark

also uses), except that I assumed a finite number of discrete

universes, whereas you stated the definition in terms of measures.

I've just reread your post about the first paradox and will comment

on it later.

Some intervals may have a greater measure, but surely they have

equally many real numbers in them. That follows from the fact that R

is a dense order-type.

_____________________________________________________

Nick Bostrom

Department of Philosophy, Logic and Scientific Method

London School of Economics

n.bostrom.domain.name.hidden

http://www.hedweb.com/nickb

Received on Sat Feb 28 1998 - 03:49:35 PST

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