On 11 May 2015, at 09:14, 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."
That is in the context of keeping physical supervenience, to go toward
the absurdity.
The brain is necessary, like all universal and non universal numbers
in the relevant relations.
It is just hat the "physical brains" are the result of the FPI on an
infinity of computations.
I reduce the mind-body problem to the problem of explaining the belief
by machine in bodies, using as theory of mind computationalism +
computer science.
You go on to say that the appearance of matter cannot be based on a
notion of primitive matter.
Yes. When assuming comp, with comp in the sense of Church-Turing. (Not
in the sense of some notion of physical computation, which I consider
as a physical implementation of a computation)
But these are different things.
Yes. One is real (the apperance of matter), and one is not real (the
primitive substancial matter).
Assuming comp. And I give the argument.
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.
Of course.
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,
It is not a belief. If *you* belief it is a computation, just tell me
which combinators it is, or which program it is.
At step seven, step 8 is not that astonishing, as you know that you
consciousness is attached to infinities of digital histories going
through your state below the substitution level.
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 avoid ever saying that consciousness is Turing emulable.
Consciousness is not even definable, like knowledge and truth.
But assuming comp; which is only that I survive a functional digital
substitution, then your consciousness here and now is not associated
to "one" computation, but to an infinity of them, and indeed can
differentiate itself, well, a bit like QM suggests.
Comp explains why math play a role, but also why the physical looks
quantum, and this informally, with UDA, and formally, with AUDA.
The argument is then that if the assumption of physical
supervenience (supervenience of consciousness on a physical brain)
leads to a situation in which consciousness would appear to be
supported by something (the film) which is not a computation, then a
contradiction has been reached, and the idea of physical
supervenience must be wrong (if comp is correct).
Right.
That makes sense, but I did not previously accept this because my
intuition was not that the projection of the film would not
reconstitute the original conscious moment. The important point that
is now clear, is that you claim that projection the film does not
constitute a computation, so cannot support consciousness. I
disagree with this. As Russell has suggested, projecting the film
can very well be considered to be a computation.
In the Church-Turing sense? You have shown not knowing the definition.
I will not ask you which one?
We have to ask what constitutes a computation in the context of this
discussion. The starting point is that part or all of the brain is
replaceable by a computer -- the brain is Turing emulable. So it
seems reasonable to define a computation as a mapping between some
input and some output that is Turing emulable.
As long as you don't say physical input and physical output, it is OK.
And the computation is not the mapping, but the sequence of step of
some machine making the mapping.
In other words, one can replace the device that takes some input to
produce some particular output with a general Turing machine.
Comp bet that there is a level where this can be done. (If not, you
could argue that a program without input and output compute all
dreams, which is false (assuming comp)).
That mapping from input to output would then be considered a
computation in the terms of the present discussion of the comp thesis.
Not just the mapping, but the sequence of step done by a universal
machine making that computation. At some point, if we want be precise,
we have to fix the universal "base", the one in which we define all
the others.
Defined in this way, it is clear that projecting the movie film on
to the physical substrate is nothing more than a general
computation. The input is a source of light directed on to the film,
and the output is the image focussed on the screen (or brain
substrate).
I can accept that, but this is just the computation of a, well, we
called that a projection. It has nothing of the complexity of the
"original computation". If you make a hole in the pellicle, the movie
will not change, the all will provides the right outputs for the
inputs. It is only description of states, mimicking a computation.
You can ascribe consciousness to it, as you can ascribe consciousness
to people, but not in virtue of making a computation, only in virtue
of being a computation in arithmetic, having the right relative self-
referential relation with its most probable arithmetical or
combinatorial history.
If you like, to use Russell's terms again, the film is a program
that is run through the projector as a computer. This process is
completely emulable by a Turing machine. In fact, digital
projections of moving images are routinely performed on general
purpose digital computers. The film (program) can be stored
digitally, and the light source and screen can also be realized
digitally.
OK. But that computation is not the one done by the boolean graph. It
is another computation, a much more rudimentary one.
The claim that the film (and projection) is not a computation is
thus false.
Not in the sense relevant for the argument.
It is a computation in exactly the same way that the brain function
replaced by a Turing machine in the "yes doctor" step 0 of the
argument is a computation. So the MGA does not establish the
conclusion that "consciousness can no longer be related to any
physical phenomenon whatsoever (i.e., brains in skulls), nor can any
subjective appearance of matter be based on a notion of primitive
matter."
Study, or let me explain what is a computation, in the most standard
theory today.
You betray that you don't try to understand a result, making it look
like it was extraordinary. But I think you go and jump far to quickly
to conclusion.
A chance that you are polite and can admit misunderstanding.
In fact, the MGA seems to have very little to do directly with the
hypothesis of primitive physicality. The argument appears to be that
if physical supervenience (a different notion than primitive
physicality)
Physical supervenience presuppose primitive physicality *in* the text
of the materialists.
But of course, a form of physical supervenience has to be justified
from comp, as it looks that mind and matter are different but *can*
cooperate.
leads to a contradiction with the comp hypothesis, then physical
supervenience must be abandoned. Extending this line of thinking, it
appears to be suggested that if physical supervenience is abandoned,
there is no remaining role for primitive physical matter in the
understanding of consciousness. The argument is less clear at this
point, but something of the sort seems to be implied.
You progress.
But if the notion of physical supervenience cannot be ruled out,
then the way is open for primitive physicality.
Indeed, comp impliees that there is a physical primitive reality, and
indeed the same for all universal machine. But it is more complex, as
the physical appears on different sorts of points of view.
But that "primitive physical reality" is still not conceptually
primitive, it is the FPI on all computations.
The comp argument, which claims that the appearance of the physical
can be extracted from the UD
Not "can be extracted". despite I have extracted already the logic of
the observable, and it has the shape needed for some Gleason theorem
in artihmetic, I do not claim that the physical can be extracted from
the UD.
But I do say that the physical *has to* be extractable from the UD.
So if someone shows that physics cannot be extracted from arithmetic
(which is still possible after UDA), it means that comp is refuted.
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.
Absolutely. Only AUDA provides evidence that comp might be correct,
thanks to Gödel, and thanks to the QM (and double thanks to MWI).
I just give a problem to the computationalist, and shows how tha
machine itselfs answers to the problem.
I am really a scientist, by which I mean that I do make public my
personal conviction, if there is any.
I am a logician and I show that we cannot marry mechanism and
materialism and a form of epistemological consistency. That might help
as both are unfortunately believed by many.
Bruno
Bruce
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