On 07 May 2015, at 14:45, Bruce Kellett wrote:
I find that discussions around the comp thesis keep coming back to
the 'Movie Graph Argument' (MGA). Each time I read one of the
accounts in Bruno's SANE04 or COMP(2013) papers, or Russell's 'MGA
Revisited', I get the feeling that something crucial to the argument
is missing.
That looks promising.
The account in COMP(2013) is probably the most detailed, so I will
look at this in some detail. The MGA (FGA) is introduced as "a
direct Mechanistic argument showing that consciousness ... cannot
possibly supervene on physical activity of the brain." This is
supposed to be shown by deriving a contradiction from the assumption
of physical supervenience.
"Direct meant that you don't need UDA1-7, from the logical point of
view. of course you need to be consciously assuming step 0, (CT+YD).
CT gives the notion of computation, by allowing to take any Turing
universal complete base. I choose two or three to help people to see
that what will be derived does not depend on the choice of the
universal computation base. I choose RA, the SK-combinators, the
diophantine polynomials).
We can use an original biological brain, or an equivalent digital
replacement -- it does not make any significant difference to the
argument. The first point is that in some conscious experience, be
it a dream or anything else, there might be a portion of the
'brain' (in quotes because it can be biological or digital) that is
not activated, so this can be removed without affecting the
conscious experience. More generally, we suppose that there is some
part of the 'brain' that is required, but is defective for some
reason. However, serendipitously, when that part is required, some
cosmic event luckily stimulates the required activity, so that the
physical activity of the 'brain' is maintained, and it corresponds
to the actual physical activity relevant for that computation. This
breaks counterfactual correctness, but if the 'dream' and the
processing is properly determined, the physical activity
corresponding to the computation, and relevant to it, is maintained.
Counterfactual correctness is thus shown not to be relevant to
*that* conscious experience. If the lack of counterfactual
correctness were able to change the personal experience, then the
brain could recognize where its internal inputs came from, which is
considered to be absurd since the assumption does not provide
cognition of the elementary parts of the computing machinery.
So far, so good. The MGA seeks to extend this line of reasoning to
show that the physical activity is not relevant at all. We image
that we are able to make a film of all the internal activity of the
'brain' during some conscious experience. (A dream if we wish to
reduce dependence on physical inputs and outputs.) We now run the
computation again after breaking some or all of the original
physical connections in the 'brain'. But at this time we also
project the film directly on to the machinery. Now, when the broken
connections are needed, despite the fact that they cannot give the
relevant outputs, the machine will still perform the original
physical activity relevant for that computation -- the movie, which
comes from a film of the correct activity, will supplement any
lacking information. The movie plays the role of the lucky cosmic
event in the previous example.
Now the first person experience will be absolutely identical to the
one which would have been obtained by the unbroken machinery. We can
eliminate more of the machinery, indeed we can eliminate /all/ of
it, without changing an active consciousness into a fading
consciousness, because this would be experienced by the subject,
contrary to the assumption that the person is never conscious of any
part of the internal machinery.
Counterfactual correctness might be restored at any stage by adding
additional counterfactual machinery, but, as before, this does not
really make any difference. Counterfactual correctness is relevant
only to the general requirement that different inputs can give
different experiences, but we are always using the same inputs here
as we repeatedly run the same program, although with less and less
of the original machinery intact -- always providing the missing
bits from the film of the original conscious computation.
Again, this all seems reasonably clear,
So far, so good.
but then the argument becomes very clouded, and it is not at all
clear what conclusions are being drawn directly from this thought
experiment. Bruno talks about the possibility of lowering the level
of substitution for the digital 'brain' replacement.
Here you make a big jump. You have stopped the reasoning above. I
doubt that lowering the substitution level is part of the MGA. It is
only part of a specific type of attempt to refute the argument.
He also mentions the MWI of quantum mechanics, as suggested by
Russell as a way to overcome the "non-robust universe" objection to
the dovetailer. The relevance of these comments is quite opaque to
me. Because then Bruno simply says: "Then, as an applied science in
the fundamental realm, we can use Occam's razor to eliminate the
'material principle'."
Yes, because computationalism (with some understanding of what
computations are, of course) entails that the physical has to emerge
from the limit of a sort of "measure" competition between all
universal number.
To invoke an Aristotelian Primary matter to select "our physical
reality" among the infinities made by the universal numbers is just
preposterous.
I mean, it looks just like invoking a God to avoid doing the math
before.
The conclusion is "the FGA (MGA) shows that any universal machine is
unable to distinguish a real physical realm from an arithmetical
one, or a combinatorial one, or whatever initial notion of Turing
universality is chosen as initial basic ontology." Hence,
consciousness is not a physical phenomenon, nor can it be a
phenomenon relating to observed matter at all. Consciousness can no
longer be related to any physical phenomenon whatsoever, nor can any
subjective appearance of matter be based on a notion of primitive
matter.
I might express myself badly, as consciousness (especially human
consciousness) can be physical, but in the Platonist sense of
physical, given that comp will justify a definite physical level, the
"matter" emerging from the bet on the consistent continuations. It
emerges from those infinite sum, and probably from some manner to
exploit the FPI random oracle to entangle computations to dovetailing
on real or complex space (to get the right persistent relative measure).
I hope I have summarized the argument as in COMP(2013) sufficiently
accurately for the present purposes. Most of the above is direct
quotation from Bruno's text, with paraphrases in some less
significant areas in order to shorten the presentation.
You have been good on the beginning, but then it looks like you jumped
to the aftermath modes.
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.
We can define the physical by the "predictable observable", then by
the FPI, we have just that inflation of computations, as there are an
infinity of different computations going through my current states.
You say the physical wins, which becomes tautological in the comp
perspective. In the paper you mention, despite MGA does not need UDA
for his point (the incompatibility of physical supervenience and
comp), but the reader of the paper is supposed to have read the UDA,
and MGA is, there, seen as the elimination of the move to a non robust
physical reality "A small universe", or physicalist ultrafinitism
(like Sean Carroll).
I am sorry, but this just does not follow.
You have been too quick. You should maybe quote the first long passage
where I go from what you understand to what you don't understand.
You have kindly confess you are not really aware of the Gödel-Church-
Turing-Kleene-Post-Markov creative bombs (the universal machine and
the Löbian machines).
This extends Everett's embedding of the physicist in physic to the
embedding of the mathematicians into the arithmetical reality.
At first sight, it looks like it leads to an inflation of realities
possible, but then this is what some suspect in the physical reality
too, and we have to compare both.
The original physical functionality is admitted to be still intact
-- provide, admittedly, by the projected movie, but that is still a
physical device, operating with a physical film in a physical
projector, and projecting on to the original (albeit damaged)
physical machinery. How has the physical element in all of this been
rendered redundant?
By UDA1-7, we have already the picture of what the observable are if
the physical universe run the UD: it is that measure on the
computations going through your relevant *relative* comp states.
You forget that computations are defined at the start (step zero) in
arithmetic (or in combinatory logic, ...)
MGA shows that if you survive through comp *qua computatio* (without
adding magic), you need to add magic to make matter, or anything,
selecting your consciousness among the infinities which are *emulated*
in arithmetic.
Primary matter is not redundant. It is useless. with MGA shows that it
becomes a God-of-the-gap, for lazy people who does not want to the
math. Just let us see.
The original functionality of the 'brain' has been preserved by the
movie;
The description of the relevant state have been preserved.
the conscious experience is still intact even though much of the
original functionality has been provided by another external
physical device. How does this differ from the original "Yes Doctor"
scenario in which the subject agrees to have his brain replaced by a
physical device that simulates (emulates) his original brain
functionality? I submit that it does not.
It is because it does not, indeed, and because of the insanity you
need to believe that a movie of a computation is a computation, that
we conclude that consciousness does not supervene on the movie
projection, and does not supervene of the physical activity of the
brain. But as comp is defined in term of computation, we are not
obliged to abandon comp, and attach consciousness to the computations
in arithmetic (the reader is supposed to have read and understand
UDA1-7, at this stage).
The only difference between the movie replacing the functionality of
the original experience and having that functionality replaced by a
computer would seem to be that the computer can emulate a wider
range of conscious experiences -- it is 'counterfactually correct'
in that it can respond appropriately to different external inputs.
The film, being a static record of one conscious experience, cannot
do this. But it has been admitted that the film can reproduce the
original conscious experience with perfect fidelity.
No, it has only been shown that the physical supervenience thesis
entails this.
But there are 0 computation in the movie, so this is comp-absurd, so
we drop out the physical supervenience, and embrace the new comp
supervenience thesis, which is given by the UD + the internal FPI
(later modeled by the intensional variant of Gödel's predicate).
And the film is every bit as physical as the original 'brain'.
No doubt on this.
So the physical has not been shown to be redundant.
The *primary physical* has been shown meaningless, or magical,
because the physical has to be redefine by a general statistics on all
(finite pieces of, and their union) computations.
It cannot be cut away with Occam's razor after all. If it were,
there would be no conscious experience remaining.
Well, if you prove that, from the result here, you refute comp. And
all I did, is to provide the tools to test this.
But I think that you just don't integrate enough the fact that the
computations are emulated in the (tiny sigma_1) arithmetical reality,
in a sense similar that a time parameter is emulated in a block
universe.
The least that the sigma_1 reality gives, when we assume comp, is a
mindscape.
I conclude that the MGA fails to establish the conclusions that it
purports to establish.
Always so quick, you are. I think you jump above the place where you
should say: I disagree with this, but probably because you have not
really go through the step seven, the once which requires the Church-
thesis, and the concrete robust universe. The reversal is made
obligatory at that stage, with a precise, even if fuzzy, redefinition
of physics (the (machine) science of the observable). At that stage,
you can do the Sean Carroll move and opt for taking UDA1-7 as a proof
that comp entails we live in a small universe. But then MGA shows that
such a move, although still logically possible, has to add some
magical property to the primary matter to be able to play the role of
the selector.
Bruno
Bruce
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