On 08 Jun 2015, at 01:14, meekerdb wrote:
On 6/7/2015 3:00 PM, LizR wrote:
On 8 June 2015 at 05:08, Bruno Marchal <marc...@ulb.ac.be> wrote:
On 07 Jun 2015, at 18:35, John Clark wrote:
On Sat, Jun 6, 2015 Bruno Marchal <marc...@ulb.ac.be> wrote:
>> An event is just a place and a time; are you saying that
mathematics is incapable of handling 4 coordinates?
> Of course, applied mathematics exists, and you can represent
event in mathematics, but you shopuld not confuse something (a
physical event) and its mathematical representation.
I am not confusing that but I think sometimes you might be
confusing a physical thing with the language (mathematics) the
descriptive representation of the thing is presented in. Or maybe
not, maybe you're right and mathematics is more than just a
language and is more fundamental than physics; nobody knows
including you.
Nobody can know. But we can reason from hypothesis. With the
computationalist hypothesis, the immateriality of consciousness is
contagious on the possible environment. Nobody pretends this is
obvious, especially for people stuck at the step 3.
The question being asked is, why hypothesis best explains
consciousness? Comp attempts to take the default materialist
assumption, that consciousness is a (very, very complicated) form
of computation, and to derive results from that assumption.
Hence what I've called comp1 is the default materialist hypothesis
(also known as the strong AI thesis, I think) - this is more or
less equivalent to the idea that a computer could, given a suitable
programme and resources, be conscious. From this Bruno attempts to
show, via a chain of reasoning, that the computations involved have
to take place in arithmetical reality ("Platonia"). This conclusion
I call comp2. The task of anyone who disagrees is simply to show
that comp2 doesn't follow from comp1.
There are various ways to try to show this. One is to doubt the
starting assumptions ("comp1"). The starting assumptions include
the idea that simple arithmetic exists independently of
mathematicians - that 2+2=4 was true in the big bang, for example.
I think that assumes that "true" and "exist" are the same thing.
You have said this often, but that does not make sense. But we do
believe in classical logic, and so accept the rule P(n) ===> ExP(x),
for n being any number. So we do accept that 2+2=4 is enough to infer
that it exist a number x such that 2 + x = 4.
One can affirm that Watson was Holmes assistant without admitting
that either one existed.
... existed in our local physical reality. But if define precisely
enough, we can show that Watson exists in arithmetic, plausibly not in
a way directly accessible to us.
So while everyone agrees that 2+2=4 by definition, it's not so
clear that arithmetic objects exist.
It is as much clear than when you say that prime number exists. And it
is explained how to recover physical existence from it. It is
phenomenologic existence, of the type [2]<2>Ex [2]<2> P(x), with [2]
being the box of the Z1*, X1* or the S4Grz1 mathematics.
The universe appears to obey certain bits of methematics to high
precision, or alternatively you could say that various bits of
maths appear to correctly describe the behaviour of the universe
and its constituents to high precision. So that is the "which comes
first?" question, which as you correctly say we can't know (indeed
we can't know anything, if "know" means justified true belief,
apart from the fact that we are conscious, as Descartes mentioned).
Note that Bruno rejects the conditioning on "justified". Plato's
Theaetetus dialogue defines "knowledge" as "true belief". I think
that's a deficiency in modal logic insofar as it's supposed to
formalize good informal reasoning. But I can see why it's done;
it's difficult if not impossible to give formal definition of
"justified".
On the contrary. Gödel provides a formal justification of "justify"
which I take as equiavalent with "proof", that is Gödel's beweisbar.
So I don't reject the conditionning on justify, I exploit it.
Then informal justification is given by the Thaetetical variant []p &
p. It obeys S4, it is not 3p definable by the machine, and so is not
formalizable (although it is meta-formalizable at the proposotional
level), ...
So one can doubt comp1 by doubting either that consciousness is a
computation, or that maths exists independently of
mathematicians.
Then one can doubt the steps of the argument. I personally find
little to doubt, assuming comp1, until we reach step 7 or 8, or
whichever step is the MGA. (There has been a lot of heat about
pronouns, but as far as I can see this hasn't made a dent in the
arguments presented.)
So the other main point of attack is at the comp2 end, so to speak,
with the MGA. There is Brent's "light cone" argument, which IMHO
seems unconvincing because one can make a "cut" between a brain and
the world along the sensory nerves - this is basically saying that
a person could be a brain in a vat, and never know it. But it also
fails if one can in theory have an AI, because an AI is by
hyopthesis a digital machine and could therefore could be re-run
and given the same inputs, and due to the nature of computation
would have to repeat the same conscious experiences.
Both of those scenarios assume that there was an external world with
which the brain/AI was related to in the past and which provides
meaning to the computational processes that are ex hypothesi now
isolated from the world. The relation need not even be direct, i.e.
the AI was constructed by a programmer whose knowledge of the world
provides the meaning. But without some such relation it's hard to
say that the computational processes are *about* anything, that they
are not just noise.
But if you use that relation in some non Turing emulable way, then
comp is false.
And if you use that relation in some Turing emulable way, the argument
resume (perhaps at some deeper level, but that does not change the
consequences, unless you add enough magic).
And then that description falls foul of Bruno/Maudlin's argument
about leeching away the material support for the computation until
it is turned into a replayed recording. At this point we can use
"Russell's paradox" - sorry, I mean argument - that a recording of
such complexity may indeed be conscious. The MGA seems to hand-wave
a bit about this whole process - like the Chinese room, we "simply"
record the activities of the processing devices and then "simply'
project the movie onto the system, and so on, leaving aside the
Vast size of the envisaged apparatus. Nevertheless, if we assume
comp1 then we assume by hypothesis that a recording isn't conscious
(only a computation can be conscious, according to comp1). So
that's really a comp1 objection.
A good point. I think comp1 is not very well defined and that leads
to the ambiguity in the MGA. The intuition is that consciousness is
due to some special kind of activity of the brain.
That is a starting intuition, but it is shown false. Eventually,
consciousness is in Platonia, more on the side of "p" than "[]p" in
the []p & p definition.
Consciousness is just not produced by the activity of the brain. After
the reversal, we have that the appearance of brain activity belongs to
consciousness.
It must be some kind of information processing and that implies it
can at least be approximated by digital computer. But to say it
*is* computation, ala Turing, is really going a little further: It's
assuming that the relation to the afferent and efferent nerves can
be abstracted as well as the brain processes, and in fact this
abstraction is, I think, contagious and it implies abstracted bodily
processes, physical interaction of the body with the environment,
the environment with the universe,... Or taking the contagion the
other way, it implies that the physical existence of the computation
was an essential part - even though "physical existence" is not
locally defined and is only relative, holistic concept.
OK.
Bruno
Brent
So the question in the end is which is the most reasonable
hypothesis. How does materialism explain
consciousness? How does comp explain the appearance of a material
universe?
Over to you.
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