On 09 Sep 2015, at 23:42, Brent Meeker wrote:
On 9/9/2015 10:27 AM, Bruno Marchal wrote:
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,
But can computationalism give a coherent account of this?
Apparently, yes. The UD argument, and the relation between non
computability and incompleteness, suggests to define belief by the
formal provability, and observable a a provable-and-consistent (true,
or not) Sigma_1 sentences. And that indeed provides a quantization,
and with some luck the right "tensor product" and the arithmetical
"Gleason theorem".
Doesn't the UD imply at every set of events will have many
(countably many?) causal histories and infinitely many causal futures.
Which is why the computationalist should be happy to see that this is
testable, and in a sense already tested.
I agree with Deutsch and Feynman on this: the whole mystery is already
in the two slits experiment. I have just zero explanation, consistent
with computationalism and special relativity, which does not give a
physical role to the relative superposed branches of the wave
describing whatever is enough real to predict the outcome. I think we
keep determinacy, locality and loss only the normal amount of
contextuality due to our intrinsic ignorance on which computations
support us.
then the "many-world" is a consequence of the linearity of the wave
evolution together with the linearity of the tensor product.
But they are only "many" FAPP. Decoherence suppresses cross terms
in the density matrix, but it doesn't make them zero - and I don't
think it's even provable that there is a unique basis in which it
diagonalized FAPP.
That means only that we differentiate quickly. Without collapse, the
Schroedinger cat's kittens can be "interpreted" by a (meta)
observation of the splitting or differentiation of our first person
sharable consistent histories (but more in a logician sense than
exactly the sense of Omnes, by example).
And of course we have no theory of quantum spacetime. QM assumes
a continuous spacetime, so QM is not the last word and if
computationalism only reproduces QM it will fail when QM fails.
Nice! May be QM will fail, where comp does not. May be comp will fail
where QM does not. In a sense, comp departs from QM, because the
quantization does not lead to a "probability" (a number between 0 and
1), but more a plausibly (a number between 0 and infinity). But local
normalization are not excluded.
To be franc, despite I am a logician, and a number lover, I tend to
think that the quantum will remain with us for very long, as it has a
plausible logico-arithmetical origin. It is the Hamiltonians or
Lagrangians, and the notion of time, space and energy which might be
more "comp" fragile, or perhaps necessitate the "winning" universal
numbers to be groups, that might help the "relative measure problem".
The everything theories might eventually just be any "universal
machine": each of us *are* theories of everything. Yet, mathematical
logic offers the canonical theology of the classical universal
machine. Its soul is intuitionist, and its matters seems to be quantum
(classical and intuitionist).
A more complex machine can study the theology of a (the truth
about ...) simpler machine that she trust, but she can't lift that
theology on herself without taking some risk, and she would
"blaspheme" in case she take such a move for granted publicly. All
machine's theologies have a trap, which can only been prevented by
repeating that we don't know the truth, and that saying "yes" to a
doctor, or saying "no", is a question of personal right, not truth.
But would it be true, despite our inability to have any certainty
about that, it follows logically, + the usual Occam, that the
fundamental theory is the universal machine theology, and physics,
both the quanta and the qualia, is a part of it.
Bruno
Brent
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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