On 09 Sep 2015, at 07:55, Quentin Anciaux wrote:
2015-09-09 7:39 GMT+02:00 Brent Meeker <meeke...@verizon.net>:
On 9/8/2015 8:20 PM, Stathis Papaioannou wrote:
On 9 September 2015 at 12:44, Bruce Kellett <bhkell...@optusnet.com.au
> wrote:
On 9/09/2015 12:26 pm, Stathis Papaioannou wrote:
On 9 September 2015 at 10:43, Bruce Kellett <bhkell...@optusnet.com.au
> wrote:
On 9/09/2015 9:30 am, Stathis Papaioannou wrote:
On 9 September 2015 at 09:23, Bruce Kellett <bhkell...@optusnet.com.au
> wrote:
On 9/09/2015 8:56 am, Stathis Papaioannou wrote:
On 8 September 2015 at 22:11, Bruce Kellett <bhkell...@optusnet.com.au
> wrote:
On 8/09/2015 9:14 pm, Stathis Papaioannou wrote:
On 8 September 2015 at 20:48, Bruce Kellett <bhkell...@optusnet.com.au
> wrote:
On 8/09/2015 8:40 pm, Stathis Papaioannou wrote:
On 8 September 2015 at 17:39, Bruce Kellett <bhkell...@optusnet.com.au
> 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.
After the coin has been tossed a few times, you (or one of the
entities identifying as you) will say that, despite the opinion he
expressed on 9th September on the Everything List, it does seem
that he has survived the duplication and that heads comes up about
half the time.
But he would say the same thing if only one fork of the program were
executed at each branch. So whether the other branches are
executed is not related to observations.
Hence probability is not linked with true randomness but from
appereance of randomness from a 1st person POV.
As for Bruce, could you then be honest, and simply say you don't
believe in the many world interpretation and don't want to explore
it... yes we're talking mostly metaphysics on this list, if you
dislike it, I wonder what you're doing here.
Indeed the point is notably that we can reason about this, that is
doing science, so that we never disagree except about the choice of
the assumptions.
Now, I disagree with Bruce, and I guess many philosophers and
scientists, except Deutsch (on this), but I do think that QM (without
collapse) is a theory of many worlds (in a perhaps admittedly more
abstract than usual notion of world).
If we define a physical world by a set of events close for
interaction, then the "many-world" is a consequence of the linearity
of the wave evolution together with the linearity of the tensor
product. People wanting one definite physical reality need to
speculate about a selection principle.
Then computations are athmetical notions, and bu virtue of (provable)
true relations among numbers, all computation are realized in a tiney
part of the arithmetical reality, in which case we get the many dreams
or histories, once we look at the realizable computational relative
"mental states".
Bruce seems coherent to me, just that he assume that personal identify
is determined and make unique by a continuous analog (non digital)
physics.
Wit computationalism we expect a continuum physics, but only because
we are muliplied continuously on different and divergent computational
histories + "real oracles".
Bruce assumes a physical universe, and betrays his Aristotelian
assumption when saying that something is a speculation if not seconded
by physical evidences.
A platonist can trust physical evidences for abandoning a theory, but
he will remain skeptical on any identification between reality and the
physical evidences or the last non refuted theory unifying those
evidences, which, for him, should be explained from simpler
principles, and not avoid the main question (why consciousness, why
does that hurt?) which are lost in any 3p extensional theory (like
physics, or classical analysis).
Bruce theory is coherent, but the price is that even simulating him at
the string/brane level, or whatever theory unifying gravity with the
quantum, and this with 100^100 real decimals exact (fr the complex
amplitudes) will not make it possible for a conscious being to
manifest itself. As it it doubtful that such simulated entity will
behave differently than a human being (or the string/brane theory is
refuted!), it means that such theory make zombies possible.
We are just wittnessing the Aristotelian resistance, but Bruce is
logically correct to resist computationalism, and the "literal
interpretation of the double linearity of QM", which is more than
welcome for a computationalist as it guaranties the sharing of the
computations: it saves us from solipsism, and that is why it is
encouraging that the physical modalities seems to go toward the
quantum mathematics too.
What a thread! The question debated can be sum up by am I a real
number or a natural number?
Bruno
Quentin
Brent
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