On 5/11/2015 6:54 PM, Bruce Kellett wrote:
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.
Why? Have you proven that consciousness supervenes on a record?
.......
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.
But how do you know this. Consciousness is somewhat mysterious. Bruno starts with idea
that you can replace part of the brain with something that is I/O functionally identical.
Saying yes to this doesn't commit you saying that a recording is functionally identical.
You would very likely only say yes if the device were counterfactually correct for at
least a large range of inputs. So it certainly doesn't follow from "saying yes to the
doctor" that you must also agree that a recording will instantiate consciousness.
That a recording is conscious is plausible because supervenience on a sequence of physical
states is plausbile. But it has its own problems: Like the rock that computes everything,
the sequence of states may be conscious of everything.
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.
I think the concept of separate conscious moments is incoherent. Conscious "moments" need
to have duration and to be in overlapping sequences, and they need to occur in reference
to an environment.
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.
I think you are equating a conscious moment with a state of the dovetailer. I think a
conscious moment, a thought, must correspond to a long sequence of dovetailer states which
may not be identical but only 'similar enough' at a classical level.
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 all depends on continuous functions. I don't think anything similar applies to
digital computations.
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.
That's why Bruno wants to model consciousness as a bundle of threads of computation. The
bundle can divide and diverge presumably modeling Everett's MWI.
Brent
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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