Hal,

It seems to me that you are introducing a notion of physical universe, 
and then use it to reintroduce a notion of first person death, so that 
you can bet you will be the one "annihilated" in Brussels.

You agree that this is just equivalent of negating the comp hypothesis. 
You would not use (classical) teleportation, nor accept a digital 
artificial brain, all right? Do I miss something?

Bruno


Le 20-juin-06, à 08:47, Hal Finney a écrit :

>
> I'll offer my thoughts on first-person indeterminacy.  This is based
> on Wei Dai's framework which I have called UD+ASSA.  I am working on
> some web pages to summarize the various conclusions I have drawn from
> this framework.  (Actually, here I am going to in effect use the SSA
> rather than the ASSA, i.e. I will work not with observer-moments but
> with entire observer lifetimes.  But the same principles apply.)
>
> Let us consider Bruno's example where you are annihilated in Brussels
> and then copies of your final state are materialized in Washington and
> Moscow, and allowed to continue to run.  What can we say about your
> subjective first-person expectations in this experiment?
>
> Here is how I would approach the problem.  It is a very straightforward
> computational procedure (in principle).  Consider any hypothetical
> subjective, first person stream of consciousness.  This would basically
> be a record of the thoughts and experiences of a hypothetical observer.
> Let us assume that this can be written and recorded in some form.
> Perhaps it is a record of neural firing patterns over the course of the
> observer's lifetime, or perhaps a more compressed description based on
> such information.
>
> The question I would aim to answer is this: for any proposed, 
> hypothetical
> first-person lifetime stream of consciousness, how much measure does
> this hypothetical subjective lifetime acquire from the third-person
> events in the universe?
>
> The answer is very simple: it is the conditional Kolmogorov measure of
> the subjective lifetime record, given the universe as input.  In other
> words, consider the shortest program which, given the universe as 
> input,
> produces that precise subjective lifetime record as output; if the 
> length
> of that program is L, then this universe contributes 1/2^L to the 
> measure
> of that subjective lifetime.
>
> Note that I am not trying to start from the universe and decide what 
> the
> first-person stream of consciousness is; rather, I compute the 
> numerical
> degree to which the universe instantiates any first-person stream of
> consciousness.  However, this does in effect answer the first question,
> since we can consider all possible streams of consciousness, and
> determine which one(s) the universe mostly adds measure to.  These 
> would
> be the ones that we would informally say that the universe 
> instantiates.
>
> Now, let me illustrate how this would be applied to the situation in
> question, and some other thought experiments.  Specifically, let us
> imagine three hypothetical streams of consciousness: B goes through 
> life
> until the moment the subject is annihilated in Brussels, then stops.
> W goes through life as does B but continues with the life experiences
> from Washington.  And M is like W, going through life until the event
> in Brussels but then continuing with the events in Moscow.
>
> Normally we only consider first-person experiences like M and W when
> we discuss this experiment, where the consciousness "jumps" to Moscow
> or Washington respectively, but it is also useful to consider B, which
> corresponds to dying in Brussels.
>
> Let me first deal with a trivial case to illustrate one of the issues 
> that
> arise when we compare first-person experiences that stop at different
> times.  Imagine a conventional lifetime where a person lives to a ripe
> old age of 90.  Now imagine the truncated version of that which we
> cut off arbitrarily at age 50.  Obviously the universe will contribute
> significant measure to both of these first-person experience streams.
> Which one will get more?
>
> I would suggest that it is actually the 90 year old lifespan which
> will have more measure.  The reason is because any program to turn the
> third-person record of all events into a meaningful, compact record of
> the lifetime experience is going to have to deal with the enormous gap
> between the fundamental events of physics, which happen at the Planck
> scale, and the fundamental events of consciousness, which although
> small to us are at an enormously larger scale compared to physics.
> This means that the program to do this conversion is going to have to
> be intensively data driven; it will have to identify tenuous and rather
> amorphous patterns of physical events, in order to translate them into
> the neurophysiological events that we would want to record.
>
> Given this structure, the (approximate) moment of physical death will
> be easily recognized, as it is that moment when the structure which the
> program has been built to track disappears.  The simplest program is
> going to be one that has its own built-in, implicit stopping rule.
>
> In contrast, a program which stops at some arbitrary time, like age 50,
> is goint to have to be larger, because we are going to have to build in
> the stopping rule.  And given that the average human lifetime is 
> enormous
> when expressed in the most natural physical units, the Planck time,
> it means that expressing the time to stop is going to take substantial
> program space.
>
> The conclusion is that, for a conventional life experience, the largest
> measure is contributed to first-person subjective records which span
> the whole range of lifetime from start to end.  Arbitrary subsets of
> that subjective lifespan will have less measure than the whole thing.
>
> Now, back to B, W and M.  As just discussed, the measure of B, which
> corresponds to a life which ends in Brussels, is likely to be 
> relatively
> substantial.  However this hypothetical teleporting or copying machine
> works, we stipulate that the guy who started in Brussels is not there a
> moment later.  It's likely that a straightforward program which has 
> been
> tracking neural events by virtue of their exceedingly slight impact
> on the Planck scale is going to be thrown off by this new process.
> Therefore a relatively simple program can output subjective record B.
>
> When we consider W and M (revivals in Washington and Moscow 
> respectively)
> there is still probably a fairly small program that can produce those
> records.  The main additional complication is that the program has to
> somehow be designed to be able to pick up the trail in the new city,
> to jump from recording neural events in Brussels to recording them in
> Washington or Moscow.
>
> This could be done in a couple of ways.  The simplest would be to
> hard-code the location of the new version of the person, perhaps
> as a vector from the old one.  But this could take quite a bit of
> information, as it might have to be accurate to the size of a synapse,
> a few nanometers.  Probably a better way would be to track whatever
> physical event carries the causal signal from Brussels to the 
> destination.
> Presumably something has to travel between the cities, carrying the
> information about the person, to allow him to be reconstructed at the
> destination(s).  Whatever this effect or principle is, we could write a
> program which was able to follow this signal, as the neural activities 
> in
> Belgium are being scanned or whatever.  This would allow identifying 
> the
> location of the new instance of the person, without having to hard-code
> the precise coordinates.  The third-person universe data would tell us
> where to look.
>
> This would probably not be too complicated a program, but it is
> nevertheless going to be substantially larger than program B.  B only 
> had
> to track neural events.  W and M have to be able to track both neural
> events and whatever physical principles are utilized by this copying
> and transmission process.  W and M are therefore going to have to have
> two different analysis methods, compared to one for B.  They should not
> have to be twice as big, since they don't have to actually track 
> thought
> during the transmission (we assume that thought is suspended during 
> that
> time), they just have to figure out where the new brain is being built.
> But chances are it is going to make W and M quite a bit larger than B.
>
> Compared to each other, W and M are probably almost identical.  The 
> only
> difference is that they make arbitrary different choices for which 
> signal
> to follow in tracking the copying information, in order to find where 
> the
> new instance is located.  Maybe one has a 1 bit where the other has a 
> 0.
> In all other respects the two programs are identical, and their measure
> should be the same.
>
> But, as noted above, B is substantially smaller, and as a result, B has
> a substantially larger measure.  This means that the contribution of 
> this
> third-person record of universe events to a subjective, first-person 
> life
> experience that ends in Brussels is much larger than to an experience
> which continues in either Washington or Moscow.
>
> If we consider these as three hypothetical people, one who dies in
> Brussels, one who continues in Washington, and one who continues in
> Moscow, it is the first one who is instantiated to the substantially
> greatest degree by the operation of such a copying machine as we are
> considering.  Informally, we could say that your most likely experience
> is that you will die in Brussels (bearing in mind the formal statement
> in the previous sentence).  That is how I would analyze it based on
> computational principles.
>
> Hal Finney
>
> >
>
http://iridia.ulb.ac.be/~marchal/


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