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.
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. 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 -- 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.
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.
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.
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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