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

Date: Mon, 2 Mar 1998 15:40:33 +0000

Wei Dai <weidai.domain.name.hidden> wrote:

*> > > A2. If I observe heads at time 1, at time 2 I will observe heads with
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*> > > probability 1.
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*> >
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*> > This is what want to dispute. If I observe heads at time 1 there is a
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*> > 2/3 chance that I observe heads at time 2. This might sound
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*> > paradoxical, but the strangeness, I suspect, comes from the fact that
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*> > the normal conditions for thinking about personal identity are not
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*> > satisfied when there exist several copies of one mind.
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*>
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*> How does 2/3 follow from definition A? At time 2, there are two
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*> continuations of the experimenter who observes heads at time 1: the
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*> original and the clone, both observing heads. So according to definition A
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*> the probability that he will observe heads at time 2 is 2/2 = 1.
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I agree that there are two continuations of the experimenter who

observe heads at time 2. But, I think, the total number of

continuations of the experimenter at time 2 is three: the two you

mention plus the one that exists in the other universe where the coin

landed tail. That observer-instance is no less a continuation of my

present observer-instance than are the two observer-instances that

observe heads. So the correct probability, on definition A, is 2/3.

_____________________________________________________

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 Mon Mar 02 1998 - 07:46:50 PST

Date: Mon, 2 Mar 1998 15:40:33 +0000

Wei Dai <weidai.domain.name.hidden> wrote:

I agree that there are two continuations of the experimenter who

observe heads at time 2. But, I think, the total number of

continuations of the experimenter at time 2 is three: the two you

mention plus the one that exists in the other universe where the coin

landed tail. That observer-instance is no less a continuation of my

present observer-instance than are the two observer-instances that

observe heads. So the correct probability, on definition A, is 2/3.

_____________________________________________________

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 Mon Mar 02 1998 - 07:46:50 PST

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