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.
Bruce
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