On 01 May 2017, at 04:22, Bruce Kellett wrote:
On Monday, May 1, 2017 at 10:41:44 AM UTC+10, Brent wrote:
On 4/30/2017 5:05 PM, Bruce Kellett wrote:
>
> Which is not what you said in the quote above. The quote is "first
> person experience in physics has to be a sum on all computations".
> Perhaps it is all just a typo -- what you meant was "that the first
> person experience *of* physics has to be the sum on all
computations.
> But even putting aside what "the sum on all computations" might
> possibly mean, this is still not what you say in SANE04: to quote
> again, "Physics is, in principle reduced to a measure on the
> collection of computational histories, as seen from some first
person
> point of view." A measure on some collection is not a sum over
anything.
>
> There seems to be a confusion here between what is consciousness
and
> what is the origin of physics.
As I understood it, Bruno's idea was like Julian Barbour's idea of
Everettian physics: below the classical level there are many quantum
threads which as an equivalence class constitute the (quasi)
classical
world or our experience. These are a kind of non-local, hidden
variables - non-local in the sense that they are in different
worlds =
threads of the UD computation. But of course the UD is executing all
possible programs, so in order that this have any explanatory power
you
need to show that the equivalence class we think of as being our
world
at least has greater than zero measure in some sense (this is like
solving the Boltzmann brain paradox).
In Barbour's image the threads are motions of the state vector in
Hilbert space and it is physics that it is modeled; consciousness
supervenes on the physics. In Bruno's idea the thread are...what?
subjective states of consciousness?
That was one of the questions I asked: "You bet on the existence of
a substitution level at which your consciousness is unaffected by
the digital substitution, but that is just betting on the idea that
your consciousness is Turing emulable-- it says nothing about what
happens below that level." Barbour's image is of the quantum "blue
mist". But Bruno does not have physics at this stage of the argument.
Bit I have the true sigma_1 sentences which mirrors constructively the
collection of all computations, and "really" all if you accept the
definition of computation given by Church, Turing, post, ...
(accepting that definition = accepting the Church-Turing thesis, or
Emil Post law).
In that case, we know that we are supported by infinitely many
computations, up to possible (non constructive) equivalence classes,
and they have to obey to some statistical conditions to make sense (if
not, then computationalism has to be false).
But consciousness has to be consciousness OF something.
I think this is the crucial point. Saying "Yes, doctor" is the
belief that I will not be aware of any experiential change under the
digital substitution. That means, in particular, that all my
memories are carried across intact. And my memories are of living
in, and interacting with, a physical world. So a great deal of
physics has to be transferred with the substitution.
It iis a digital substitution. A big deal of "belief in physics" has
to be transfered, but on of "physics" (which does not make much sense).
Looked at in another way, the computation that underlies my current
conscious state already include a lot of physical information.
A helpful comparison might be with Tegmark's multiverse (arxiv:
0905:1238v1). In the level 1 multiverse there is infinite space,
which contains Hubble volumes realizing all initial conditions --
including an identical copy of you about 10^{10^29} m away. This
corresponds to other threads in the UD that go through your
conscious state. These are the threads which constitute the
equivalence class that Bruno wants in order to extract physics. But
in this picture, they are just identical copies of the conscious
"you" in different universes
Except that we don't need to assume "universe", nor to define them.
Only computations, which is mathematically a precise notion (accepting
Church's thesis)
-- they are complete in themselves and are not needed in order for
the present "me" to be conscious. Of course, when one identifies the
level I and III multiverses, this just gives FPI as the origin of
quantum randomness.
Good. But the points is that this already happen with elementary
arithmetical assumption, and with computationalism, adding assumptions
to this cannot work to justify the appearance of the physical reality
(by the UDA).
Other levels of Tegmark's multiverse correspond to the other threads
of the UD which do not contain our consciousness, and which entail
different basic physical laws -- up to Tegmark's level IV, which
contains all other mathematical structures. It might be more
relevant to compare the UD to Tegmark's later idea of the
"Computable Universe Hypothesis" (CUH) which claims that all
'computable' mathematical objects are realized in some world in the
multiverse. It is hard to detect any difference between this idea
and the worlds of the UD.
The number of assumptions involved, and the understanding that physics
is reduced to machine's theology.
In fact, Bruno's three assumptions for computationalism: "Yes,
doctor", Church-Turing, and Arithmetical realism, would lead to
Tegmark's CUH just as readily as to computationalism.
CUH is refuted. The physical universe cannot be a computable "object".
It is only a persistent psychological illusion of universal numbers.
Bruno
So the measure has to pick out not only
coherent threads of consciousness but also complementary coherent
threads of physics in which the consciousness can exist. Otherwise
the
consciousness can only be conscious OF stuff independent of physics;
which Bruno thinks includes all of mathematics and I think is empty.
It's supposed to be an empirical question. That means there is some
consequence of the theory which shows up in the physics. An obvious
one, is that one's ability to do mathematics should not be affected
by
the consumption of tequila.
You have the difficulties in a nutshell.
Bruce
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