Le 16-avr.-08, à 18:02, nichomachus a écrit :

> On Apr 16, 4:54 am, Bruno Marchal <[EMAIL PROTECTED]> wrote:
>> Le 16-avr.-08, à 03:24, Russell Standish a écrit :
>>> On Wed, Apr 16, 2008 at 02:22:23AM +0200, Saibal Mitra wrote:
>>>>> First off, how is it that the MWI does not imply
>>>>> quantum immortality?
>>>> MWI is just quantum mechanics without the wavefunction collapse
>>>> postulate.
>>>> This then implies that after a measurement your wavefuntion will be
>>>> in a
>>>> superposition of the states corresponding to definite outcomes. But 
>>>> we
>>>> cannot just consider suicide experiments and then say that just
>>>> because
>>>> branches of the wavefuntion exist in which I survive, I'll find
>>>> myself there
>>>> with 100% probability. The fact that probabilities are conserved
>>>> follows
>>>> from unitary time evolution. If a state evolves into a linear
>>>> combination of
>>>> states in which I'm dead and alive then the probabilities of all 
>>>> these
>>>> states add up to 1. The probability of finding myself to be alive at
>>>> all
>>>> after the experiment is then less than the probability of me finding
>>>> myself
>>>> about to perform the suicide experiment.
>>>> The probability of me finding myself to be alive after n suicide
>>>> experiments
>>>> decays exponentially with n. Therefore I should not expect to find
>>>> myself
>>>> having survived many suicide experiments. Note that contrary to what
>>>> you
>>>> often read in the popular accounts of the multiverse, the multiverse
>>>> does
>>>> not split when we make observations. The most natural state for the
>>>> entire
>>>> multiverse is just an eigenstate of the Hamiltonian. The energy can
>>>> be taken
>>>> to be zero, therefore the wavefunction of the multiverse satisfies 
>>>> the
>>>> equation:
>>> One should also note that this is the ASSA position. The ASSA was
>>> introduced by Jacques Mallah in his argument against quantum
>>> immortality, and a number of participants in this list adhere to the
>>> ASSA position. Its counterpart if the RSSA, which does imply quantum
>>> immortality (provided that the no cul-de-sac conjecture holds), and
>>> other list participants adhere to the RSSA. To date, no argument has
>>> convincingly demonstrated which of the ASSA or RSSA should be
>>> preferred, so it has become somewhat a matter of taste. There is some
>>> discussion of this in my book "Theory of Nothing".
>> Actually, I am not sure the ASSA makes sense once we take into account
>> the distinction between first and third person point of view. Comp
>> immortality is an almost trivial consequence that personal death 
>> cannot
>> be a first person experience at all. Quantum immortality is most
>> plausibly equivalent with comp immortality if the "quantum level"
>> describes our correct comp substitution level. But this does not mean
>> that we can know what shape the comp immortality can have, given that
>> comp forbids us to know which machine we are or which computations 
>> bear
>> us.
> Why is this the case? Whether Comp is true or not, it would seem that
> the direction of physical research and investigation is in the
> direction of discovering the presumed foundational TOE that accounts
> for everything we observe. Say, for example, that it were possible to
> create in a computer simulation an artificial universe that would
> evolve intelligent life forms by virtue of the "physics" of the
> artificial universe alone. Why, in principle, is it not possible for
> those intelligent beings to discover the fundamental rules that
> underlie their existence? They will not be able to discover any
> details of the architecture of the particular turing machine that is
> simulating their universe (even whether or not they are in fact being
> computed), but I don't see any a priori reason why they would not be
> able to discover their own basic physical laws.
> Max Tegmark has indicated that it may be possible to get some idea of
> which mathematical structure bears our own existence by approaching
> from the opposite direction. Though we may never know which one
> contains ourselves, it may be possible to derive a probability
> distribution describing the likelihood of our location in the
> ensemble.
> To go back to the comments you were making about the Prestige:
> If the subject of a quantum immortality experiment finds himself
> improbably alive, is he in some sense guilty of the murder of the
> other versions of himself? Or not, since those are merely third person
> experiences.

See Quentin Anciaux's post. I will just comment your last paragraph.

> What constitutes a first person experience? It seems that
> you are defining it as an uninterrupted consciousness since comp
> implies the  "almost trivial consequence that personal death cannot be
> a first person experience at all." I am confused by exactly what is
> meant by first and third person experiences.

OK. In the UDA (Universal Dovetailer Argument) I define a notion of 
first person and third person in relation with (classical) 
The first person discourse is given by the content of a diary or memory 
of a teletransporter, and the third person discourse is the memory or 
diary content of an external observer. The difference is that the first 
person memory is copied, annihilated and reconstituted, when the third 
person memory is not. I suggest you read my SANE paper perhaps.
In the lobian machine interview I give a much more abstract definition 
of the first person. I define it by the "knower", and I borrow the 
definition of knowledge to Plato (in the Theatetus). But here the 
simple "teletransporter-based" definition of first person is enough. 
More later.



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