On 18/07/2016 1:25 pm, Stathis Papaioannou wrote:
On 18 July 2016 at 12:35, Bruce Kellett <bhkell...@optusnet.com.au
<mailto:bhkell...@optusnet.com.au>> wrote:
On 18/07/2016 12:10 pm, Stathis Papaioannou wrote:
On 18 July 2016 at 11:54, Bruce Kellett
<bhkell...@optusnet.com.au <mailto:bhkell...@optusnet.com.au>>
wrote:
I have said several times that probability is a problem for
the Everettian or MWI view. This is not a problem of defining
a measure over a possible infinite number of worlds -- though
that is certainly a problem that has not really been solved
-- but the main difficulty lies in the observation that
probability makes little sense in a situation in which
everything possible does happen. So there is no workable
notion of probability in the Everettian multiverse.
Standard quantum mechanics gets around this in a fairly
straightforward way: the "other worlds" in which alternative
outcomes occur are disjoint, with no possible future
interaction with the world in which we find ourselves. Such
alternative outcomes can thus be safely ignored because they
can have no possible effect on the observer or on his future
evolution. Decoherence ,and the irreversibility of completed
experimental outcomes, thus reduce QM to an effective
collapse situation -- there is no physical collapse, but FAPP
the other worlds have vanished from existence.
You seem to be saying that if the copies in the other worlds
effectively vanish due inaccessibility, this is fundamentally
different with regard to personal identity compared to the case
of duplication within the one world. I don't see why that should
be so. It may solve some practical problems, such as which copy
gets the possessions of the original, but these are not
fundamental problems with personal identity.
Practical problems are what is at stake in personal identity, and
the inaccessibility of other worlds solves these because we only
look for a closest continuer in the world we actually inhabit --
all others are irrelevant for any purposes whatsoever. A theory of
personal identity has to solve practical problems, and to accord
with our expectations and intuitions in difficult cases. That is
why person duplication scenarios are a problem for a satisfactory
theory.
Practical problems are very important but they do not necessarily
impact on personal identity. If God grants me a vision of my copies in
other worlds that would be interesting, but it would not make me
change my view of personal identity in general or my identity in
particular given that I already believed those copies were out there
anyway.
"Closest continuer theory" should not be presented as if it is the
standard philosophical position on personal identity, let alone the
only correct one. It has serious inherent problems, eg. it implies
that if two identical copies of you are made in a duplication
experiment then there is no closest continuer and you have not survived.
That is what I have always said happens in ties. Why is that a problem?
Note that there is a difference between Bruno's steps in that in step 3
(I think) the original continues, and thus would have at least a bodily
claim to be the unique closest continuer. In the other scenario, the
original is cut, so there can be no problem if one says in that case
that there is a genuine tie -- the original dies and two new persons are
created. Where's the problem?
Bruce
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