Well said. This clarification will go a long way towards resolving the
dispute with Jacques.
Cheers
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> Bruno Marchal, <marchal.domain.name.hidden>, writes:
> > Here is the message of Nick Bostrom where he introduces briefly
> > the SSA (in this discussion list 13/04/99):
> >
> > >The Self-Sampling Assumption (SSA), the idea that you should reason
> > >as if you were a random sample form the set of all observers,
> > >underlies many of the discussions we have had on this list. About
> > >half a year ago I discovered some paradoxical consequences of this
> > >assumption. It seems to imply that weird backwards causation and
> > >psychokinesis(!) is feasible in our world. In this small paper I
> > >describe these possible counterexamples and discuss whether they
> > >really are as paradoxical as they appear at first blush:
> > >
> > >http://www.anthropic-principle.com/preprints/cau/causation.doc
>
> Perhaps we need to distinguish a "Strong Self-Sampling Assumption",
> which is like the SSA but instead of discussing "observers", it refers to
> "observer-instants". An observer is somewhat ambiguous, not so much in
> the sense that it is hard to say what counts as an observer, but rather
> because it seems to implicitly bring in the concept of identity.
>
> I am the same observer today that I was yesterday, and will be tomorrow.
> To say that I am a random sample among all observers is to refer to my
> lifetime of experience as a single instance of an observer.
>
> The Strong SSA, on the other hand, refers not to observers, but to moments
> or instants of observation. At each moment we have to view ourselves
> as a fresh, newly selected instance among all possible observers.
> Of course, our moment of experience does include memories of a lifetime
> of past experiences, but that is not relevant to the definition of an
> observer-instant in this concept. There is no necessary equality of
> my probability of being an observer-instant now, and the probability of
> the observer-instant which corresponds to my memories of one second ago.
>
> This is especially true when we begin running our exotic thought
> experiments of quantum suicide and mental cloning. If I sit on a bomb
> and press the firing button, and it doesn't go off, it may still be
> the case that the probability of my current observer-instant is much
> less than the probability of the one just before I pressed the button.
> If I step into a duplicating machine which makes 100 identical and
> indistinguishable copies of me, the probability of my observer-instant
> after the event (but before we have begun to diverge) may be much greater
> than the probability just before the button was pushed.
>
> I think that Nick Bostrom, who (as far as I know) conceived of and named
> the SSA, was not thinking in terms of the Strong SSA. When he discusses
> "my" birth rank, he is implicitly assuming that I am the same observer
> today that I was when I was born. I think it is best, therefore, to
> distinguish the two assumptions by giving them names in this form.
>
> Hal
>
>
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Received on Tue May 18 1999 - 15:46:19 PDT