On 7/3/2015 5:57 AM, Bruce Kellett wrote:
Bruno Marchal wrote:
On 03 Jul 2015, at 02:34, Bruce Kellett wrote:
In the context of the present discussion, I would say that UDA+MGA does not entail
immaterialism.
Logically no. Episitemologically, yes. Primitive matter becomes a phlogiston or ether
sort of thing. We cannot detect it, we cannot use it, we cannot related to any
experience in physics, etc. yes, logically we can still believe in it. I have never
pretended the contrary. (I admit that in some text, I might be quick on this).
My point is that whatever metaphysical stance you take, the physical universe exists,
and our experience of it is the basis of all our knowledge.
Bruno is a Platonist (or a Kroneckerist). He thinks we know things like Peano's axioms
and logic independent of experience.
It is quite possible to accept primary physicality and interpret the universe in a
pancomputationalist framework.
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.
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. Reminding us that a
theory that explains everything fails to explain at all.
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.
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
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