On 9/09/2015 12:26 pm, Stathis Papaioannou wrote:
On 9 September 2015 at 10:43, Bruce Kellett <[email protected]
<mailto:[email protected]>> wrote:
On 9/09/2015 9:30 am, Stathis Papaioannou wrote:
On 9 September 2015 at 09:23, Bruce Kellett
<[email protected] <mailto:[email protected]>> wrote:
On 9/09/2015 8:56 am, Stathis Papaioannou wrote:
On 8 September 2015 at 22:11, Bruce Kellett
<[email protected]
<mailto:[email protected]>> wrote:
On 8/09/2015 9:14 pm, Stathis Papaioannou wrote:
On 8 September 2015 at 20:48, Bruce Kellett
<[email protected]
<mailto:[email protected]>> wrote:
On 8/09/2015 8:40 pm, Stathis Papaioannou wrote:
On 8 September 2015 at 17:39, Bruce Kellett
<[email protected]
<mailto:[email protected]>> wrote:
On 8/09/2015 4:56 pm, Stathis Papaioannou wrote:
I will ask you the same question as I did
Brent: do you conclude from the fact that
when you toss a coin it comes up either as
head or tails that the world does not split
into two parallel versions of you, one of
which sees heads and the other tails?
I would conclude that a coin toss does not
provide any evidence for multiple worlds or a
split. The only evidence we have from this
data is that the outcome of the toss is
uncertain. There is no evidence there for any
split of anything.
It is not evidence FOR a split but is it evidence
AGAINST a split?
It is evidence that the assumption of a split is
not necessary in order to understand everyday
happenings. So, by the application of Occam's
Razor, no split happens.
So you agree that we would still observe the
probabilities we do if we lived in a deterministic
world in whaich all possibilities are realised?
No, because not all possibilities happen in this world.
If all possibilities were realized in this world, then
there would be no uncertainty, no probabilities.
Possibility and actuality would be the same thing. All
the horses would win the Melbourne cup; and we don't
live in such a world.
Obviously, not all possibilities happen in this world, but
they might happen in parallel worlds that don't interact
with each other. The argument is that probabilities emerge
from this, since you don't know which world you will find
yourself in. You bet on the favourite in the race because
you think you are more likely to end up in a world in which
the favourite wins.
In other words, probabilities can make perfect sense in a
single deterministic world. This was understood a long time
ago with the development of statistical mechanics. The idea
that "all possibilities happen in parallel worlds" does not
actually make a lot of sense. There is no current physical
theory that implies this (without the addition of a lot of
unevidenced assumptions). So probabilities do not emerge from
this, they come from quite simple assumptions of randomness
and ignorance.
Probability in the MWI of quantum mechanics is problematic.
Regardless of claims to be able to derive the Born Rule in
Everettian models, all attempts fail because they are
circular -- they need the Born rule in order to have
non-interacting worlds, so you cannot then use these
independent worlds to derive the Born rule. Gleason's theorem
is no help -- it suffers from all the same problems as the
Deutsch-Wallace approach.
You don't seem to be disputing that we would still experience a
probabilistic world even if all possibilities were actually
realised, even though you do dispute that we in fact live in such
a world.
I'm not sure if you are disputing that, to give a simple model
case, if a coin was tossed and the world split in two, with one
version of you seeing heads and the other tails, the probability
of each outcome is 1/2.
Whether or not all possibilities are realized, they are not in
evidence, so their relevance to the question of probabilities is
questionable.
Your simple model case of a coin toss causing a world split is
just a made-up example to give the result you want, so again its
relevance is dubious. There is no sensible physical theory in
which the world splits on classical coin tosses.
If you can't imagine a world split, consider a virtual reality in
which the program forks every time a coin is tossed, one fork seeing
heads and the other tails. You are an observer in this world and you
have this information, so you know for certain that "all possibilities
are realised" when the coin is tossed. What would you say about your
expectation of seeing heads?
I presume you mean that the world is duplicated on each toss, with one
branch showing each outcome. We are back to the dreaded "person
duplication" problem. My opinion on this is that on such a duplication,
two new persons are created, so the probability that the original person
will see either heads or tails is precisely zero, because that person no
longer exists after the duplication.
Bruce
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