meekerdb wrote:
On 7/3/2015 5:57 AM, Bruce Kellett wrote:
Bruno Marchal wrote:
No. This does not work. Everything cannot be computable, once we are
turing emulable.
I have never understood why you say this. Given that the world is
explicable in terms of regular physical laws, then it is computable.
Unitary evolution of the wave function is a prime example of this. The
only problem might be that that laws of physics do not necessarily
give the boundary values. But multiverse models eliminate even this
difficulty.
I think he assumes (as do many proponents of MWI) that "everything
happens" in some sense, which is not computable in the limit even though
approximations to it are computable.
Yes. I was thinking in the terms in which the number of possible
histories in any O-region is finite. I.e., given Uncertainty Principle
limits on measurement, only a finite number of histories are physically
distinguishable.
Since he wants to explain all
experience, including physics, from computation, he doesn't want to
assume unitary evolution or any other physics. He just assumes all
possible computation (the UD). But this leaves the "white rabbit"
problem.
The computations of the UD include the computation which gives the
physical universe, complete in every detail (at least down the the UP
limits), so every physically distinguishable history is automatically
included. We don't need to worry about summing over computations that go
through our particular conscious state, or which have inconsistent
extensions (white rabbits). We have only to see ourselves as
instantiated in the calculation that instantiates our universe (and us
in it). No need to sum over anything. As I have said earlier, this
instantiates all of Tegmark's level I and II multiverse, and possible
levels III and IV as well.
Reminding us that a theory that explains everything fails to
explain at all.
Exactly. We see the universe around us as it is because that happens to
be the universe we are in. Nothing is actually explained, and that is
the problem with any TOE.
Consciousness supervenes on the physical brain, or physical computer
if required. In either case, it obeys regular laws, so is computable.
I don't think that follows. First, if you allow randomness then that's
not computable. Second, if you avoid randomness by assuming everything
possible gets computed then that's subject to Cantor diagonalization so
Turing computation can't compute everything; you need a hypercomputer.
And third, our best theories, QM and GR, both assume real numbers which
are not necessarily computable.
Some real numbers are necessarily not computable -- possible computer
programs are countable but the reals are not, so there are some reals
for which no program will reproduce the infinite decimal expansion. But
given UP limits in the digital universe, this problem goes away for
distinguishable universes.
Randomness is not really a problem. You might not be able to predict a
result, but you can calculate probabilities, and that is sufficiently
law like for our purposes. Of course, MWI simply computes all outcomes,
so there is no randomness.
If you interpretation of the UDA leads to non-computability, then that
itself is a strong argument against comp because it would imply that
some behaviour in the universe is not law like.
The universe is then understood in terms of computations, but these
are a consequence, secondary and not primary.
That seems self-contradictory to me. If computations are secondary,
why explain the universe in term of them?
Any physical model is secondary, yet we routinely explain things in
terms of such models.
This is what I see as a defeater of the MGA. There's another possible
reason that the movie graph is not conscious; namely that it does not
function in a context. Bruno dismisses this by saying that the context
can be included and then the argument still goes through. But it
doesn't because if the context has to include a whole world it is no
longer 'absurd' that the movie graph is conscious in that context. It
may still be unintuitive, but not absurd.
Brent
Computation is a purely mathematical, even arithmetical notion.
Without giving a theory which would be able to just give a physical
definition of computation (not using the arithmetical one) I can not
make sense of your proposition.
I don't know why you think that a separate physical definition would
be necessary. Mathematics is derived from physics, and so is computation.
Bruce
--
You received this message because you are subscribed to the Google Groups
"Everything List" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/d/optout.
