On 6/7/2015 3:00 PM, LizR wrote:
On 8 June 2015 at 05:08, Bruno Marchal <[email protected]
<mailto:[email protected]>> wrote:
On 07 Jun 2015, at 18:35, John Clark wrote:
On Sat, Jun 6, 2015 Bruno Marchal <[email protected]
<mailto:[email protected]>>
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. One can affirm that
Watson was Holmes assistant without admitting that either one existed. So while everyone
agrees that 2+2=4 by definition, it's not so clear that arithmetic objects exist.
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".
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.
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. 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.
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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