meekerdb wrote:
On 5/11/2015 12:14 AM, Bruce Kellett wrote:
Bruno Marchal wrote:
On 07 May 2015, at 14:45, Bruce Kellett wrote:
......
Now, having read this many times, and looked at the other summaries
of the MGA, I still feel that something crucial is missing. We go
from the situation where we remove more and more of the original
'brain', replacing the removed functionality by the projections from
the movie, which, it is agreed, does not alter the conscious
experience of the first person involved, to the conclusion that the
physical brain is entirely unnecessary; indeed, irrelevant.
Hmm... On the contrary: the brain is necessary. It is the primitive
physicalness of the brain which is not relevant.
That is not what you say in the paper. "Hence, consciousness is not a
physical phenomenon, nor can it be a phenomenon relating to observed
matter at all." You go on to say that the appearance of matter cannot
be based on a notion of primitive matter. But these are different
things. Elsewhere you appear to agree that consciousness does depend
on the observed physical brain. In fact, it would be foolish to deny
this given the weight of physical evidence that shows this to be the
case.
Now that I have had a couple of days away from the internet to think
about this, and have read other comments on this thread, I think I
understand better the point that was not clear to me from the
COMP(2013) paper. What your intuition claims to be absurd in the MGA
is that replaying the film can instantiate consciousness. The reason
for this is based on your belief that replaying the film is not a
computation, and since the basic assumption is of comp is that
consciousness is Turing emulable -- is in fact a computation -- we
cannot have consciousness without the associated computation.
I think this obfuscates the point. One says yes to the doctor not
because one's conscious thought is a computation, but rather because the
doctor proposes to replace part of your brain with something that will
perform ALL the computations that part of the brain could do. It is not
that consciousness is a computation, rather it is a class of
computations that will map all possible (not just actual) environmental
inputs into outputs. And that's why a recording is ruled out - whether
it would be conscious or not; it is not counterfactually adequate.
The recording is not supposed to instantiate a fully conscious person,
capable of actiang normally in a changeable environment. All is was ever
presumed to do was replace just the one conscious moment (or string of
moments) that were originally recorded. This whole argumetn about
counterfactual correctness is a total red herring.
.......
The claim that the film (and projection) is not a computation is thus
false.
No, I think it's true because it's not counterfactually correct. Whether
you call it a computation or just and look-up table is, as Russell
points out, a matter of intuition about size. How many counterfactuals
must it deal with? Whether the ultrafinitism is true or not, our theory
of the world and consciousness should not depend on there being
infinities. So within ultrafinitism all TM's can be replaced by lookup
tables. Or looked at the other way around, a sufficiently enormous
lookup table is a computer.
As stated above, counterfactual correctness is not required to reproduce
just the one original conscious moment.
So conterfactual correctness is not important for the single conscious
moment. It might be one way of saying that a conscious person is one who
can respond, more or less appropriately, to a range of physical
circumstances (external inputs), but it says nothing about separate
conscious moments.
But it is by no means clear that a need for counterfactual correctness
can be concluded from the computations of the dovetailer. The idea there
seems to be that the same conscious instant (or sequence of instants) is
reproduced many times in the dovetailer, and many of these will lead to
different continuations, implying that each instance has to be more
flexible than is required for *that* instant.
But I have a problem with this if the dovetailer is instantiating a
classical physics model of consciousness. There is an important theorem
in complex analysis that states that if two analytic functions coincide
in a neighbourhood, no matter how small, then the two functions are
equal everywhere in the region over which they are analytic. This has
its parallel in classical physics, where it can be shown that if one is
given initial data over some Cauchy surface, then the complete past and
future of that system is determined, and calculable in terms of known
physical laws.
This seems to imply that if two computations coincide for some sequence
of conscious states, then the continuations of those computations must
be identical. If they are not, then the computations do not instantiate
consciousness that is governed by deterministic physical laws. And such
moments (white rabbit moments) are presumed to have zero measure in the
dovetailer. So if two parts of the dovetailer are identical for some
conscious moment, then those computations are identical indefinitely far
into the past and into the future. (Or else they do not instantiate
regular deterministic physics.)
In fact, the MGA seems to have very little to do directly with the
hypothesis of primitive physicality.
I agree.
......
Primitive matter is a strawman. No one I've know, even Vic Stenger, has
held that matter is anything more than the ontology of one's theory of
physics. Physicist make different models and some have field
ontologies, some have spacetime, some have particles. So "matter" is
just whatever the model says it is. If the world is made of
computations then we could call computations "matter".
I agree, and it is probably important to point out that nowhere does
Bruno's argument say anything substantial, one way or another, about
primitive matter. Lots of claims, but no substantive arguments.
The comp argument, which claims that the appearance of the physical
can be extracted from the UD running in Platonia, has no greater claim
to credence than the physicalist's claim that mathematics is a human
invention, extracted from our experience of the physical world.
The choice between these might reduce to nothing more than personal
preference.
But the interesting thing about Bruno's theory is that it proposes a
solution to the mind-body problem by making both of them computations.
Aside from the UD, this is not particularly radical. If you had an
intelligent/conscious AI within a virtual environment then the
consciousness of the AI would be relative to that environment and both
of them would be computations. Bruno proposes that the relation can be
expressed in terms of what the AI would "believe", i.e. able to prove,
about the environment. I find this interesting aside from arguments
trying to defeat some imaginary "primitive physicalists". The UD is
interesting because it makes Tegmarks mathematical-universe idea more
specific, something you might be able to draw inferences from.
It might be interesting in prospect, but this is beside the point if
Bruno cannot establish his case to the general satisfaction of others;
his theory has to actually get somewhere in order to be convincing.
Bruce
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