2010/1/18 Nick Prince <m...@dtech.fsnet.co.uk>:

>> If you had to guess you would say that your present OM is a common
>> rather than a rare one, because you are more likely to be right.
>> However, knowledge trumps probability. If you know that your present
>> OM is common and your successor OM a minute from now rare - because
>> there are many copies of you now running in lockstep and most of those
>> copies are soon going to be terminated - then you can be certain that
>> a minute from now you will be one of the rare copies. This is what
>> happens in a quantum suicide experiment under the MWI. To put some
>> numbers on it, if there are 100 copies of you now, and in a minute 90
>> of those copies will be terminated, and of the remaining 10 copies 3
>> will be given a cup of coffee and 7 a cup of tea, then as one of the
>> 100 original copies according to the RSSA you have a 30% chance of
>> surviving and getting coffee and a 70% chance of surviving and getting
>> tea; i.e. you have a 100% chance of surviving. Proponents of the ASSA
>> would say you have a 3% chance of surviving and getting coffee and a
>> 7% chance of surviving and getting tea, or a 10% chance of surviving
>> overall. I think they would say something like this - the
>> probabilities may be off since the total contribution of pre/post
>> termination OM's has to be tallied up, but in any case they would not
>> say you are guaranteed of surviving. The only way I can understand
>> this latter view is in the context of an essentialist theory of
>> personal identity, according to which once a body is dead it's dead,
>> and it's impossible to live on as even a perfect copy.
> Thank you Stathis, that was a really helpful reply and has confirmed
> my own thinking on this in many respects.  I'm never quite sure why
> list members work in copies though. I am hoping you (or anyone) can
> clarify the following queries.

Copies are concrete and finite, and therefore easier to grasp than
abstract OM's. Copies could in theory be made in whatever universe we
live in, if necessary biological copies if not computer uploads (in
case it turns out the brain is uncomputable). A prerequisite to most
of the discussions on this list is a clarification of your view on
personal identity, and even in the philosophical literature this is
often discussed by reference to thought experiments involving copies,
as created by Star Trek type teleportation. Derek Parfit's "Reasons
and Persons" is a good book to read on the subject.

> 1. Can we not say that (under RSSA) my measure of existence has
> initially say 100 units and if there is a 90% chance of being blown up
> before being offered the tea or coffee then if I end up drinking tea
> my relative measure has reduced to 70 units in this branch (note the
> word relative here - I hope I'm getting this right).  If I find myself
> drinking coffee then my relative measure has reduced to 30  (my global
> measure over all universes still remains at 100 though?)

Your "relative measure" before the termination event is not relevant
and maybe not coherent: relative to what? The importance of your
relative measure is in trying to predict what you can expect for the
future. Looking forward, you can expect that you will certainly
survive since there will be at least one copy surviving. Of the 10
copies that do survive, each has equal claim to being you. Since the
ratio of coffee drinkers to tea drinkers is 3:7, you have a 3/10
expectation of ending up a coffee drinker and a 7/10 expectation of
ending up a tea drinker. So the "relative" part is in the 3:7 ratio,
whether the absolute numbers are 3:7 or 30:70 or 3000:7000. When I
consider what I will experience the next moment, I take into
consideration all the possible successor OM's (those that have my
present moment in their immediate subjective past), and my
expectations about the future depend on their relative frequency. This
is simple in the present example but becomes difficult when we deal
with infinite sets of OM's where there is a gradation between the
definitely-next-moment-me's and definitely-next-moment-not-me's.

> 2. In this way (under RSSA) my relative measure continually decreases
> within each branch(hence use of word relative) but my global measure
> across the multiverse is conserved.  According to ASSA though my
> measure deceases both across universes and in each branch - in all
> branches I eventually die as well as differentiate.

According to RSSA and the RSSA your absolute measure in the multiverse
decreases with each branching as versions of you die. According to the
RSSA this doesn't matter as at least one of you is left standing;
according to the ASSA, this does matter and you eventually die. The
only way I can make sense of the latter is if you have an essentialist
view of personal identity. Under this view if a copy is made of you
and the original dies, you die. Under what Parfit calls the
reductionist view of personal identity, you live.

> 3. Is this copy concept used because of the idea of "differentiation"
> as mentioned in Russells book on p144.   I guess in a huge universe
> there will be a very large (infinite?) number of identical me's,
> currently all in lockstep.  A single consciousness supervenes over
> these copies until such time as they differentiate due to some bundles
> going through different OM's.  The bundle's "thickness" is the measure
> of my existence.  In RSSA terms my measure of existence is always
> constant globally (  I am using a definition of measure based on Lev
> Vaidman’s measure of existence as in the link below).
> http://plato.stanford.edu/entries/qm-manyworlds/

Russell makes the point that there are two possible views of your
passage through the multiverse: (a) there are multiple versions of you
whose worldlines differentiate as time goes on and you (the subject)
are one, and only one of these versions, so that when that version
dies, it's the end for you even though your other versions might go
on; or (b) your consciousness supervenes over all identical versions
of you, and when the worldlines differentiate your consciousness is
indeterminate and differentiates according to the weighting as in the
above coffee/tea example. I actually don't think there is a difference
between the versions, even if you do choose to believe that
consciousness must supervene on one and only one particular concrete
physical process. For although my current OM may be attached to a
particular physical process, I can't know which physical process if
more than one produce the same OM, and I can't know which physical
process out of all the possible candidates will produce my next OM.
This reasoning converts (a) into (b).

Stathis Papaioannou

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