On 20 Aug 2009, at 14:30, David Nyman wrote:
>
> On 20 Aug, 10:05, Bruno Marchal <marc....domain.name.hidden> wrote:
>>
>>
>>
>>>
>>
>> Your second sentence answers the first one. Your paragraph above
>> also.
>> The current "seventh step series" is leading to the understanding of
>> what is a computation, and a machine, for a mathematician. With or
>> without assuming PM (primitive matter) there is an mathematical
>> notion
>> of computation and of computability.
>
> Ah. Well, tell me if you still want to make the point about my
> 'paragraph above', after my response on this. But on the issue of the
> understanding of what is computation, I must concede that I have much
> to learn technically - so I will be humble and try to study.
>
> But also - just to dispose once and for all of this particular point -
> I want to be sure that you understand that I'm not arguing *for*
> eliminative materialism, except as devil's advocate (I'm sure you know
> this). But one aspect of my recent discussions with Peter has been to
> bring to a focus the strict consequences of materialism, in precisely
> the honest way that you attribute to Dennett. The trouble is, that
> Dennett, having eliminated the mind and hence the notorious 'problem',
> still cheerfully carries on deploying the same mind-dependent concepts
> as though nothing had happened! In other words, his position is
> inconsistent and incoherent. It's dualism for free!
I agree. I think that Dennett agrees too, as he almost confesses at
the end of his book on "Consciousness Explained".
>
> So, in this context, let me try to understand your remark: "with or
> without assuming PM (primitive matter) there is an mathematical notion
> of computation and of computability". I would say - per Dennett, but
> understood *consistently* - that under the assumption that there is
> *only* primitive matter (i.e. material monism) - there strictly can be
> no appeal to such a notion as computation, because mathematics itself
> is eliminable per Qine. Don't misunderstand me - this is what is
> *wrong* with material monism - because to be consistent, one is either
> honestly forced to such an eliminativist conclusion (but then you must
> deny your own consciousness and all mental concepts), or you tacitly
> accept a form of dualism (but again without noticing!) So I suppose
> that when you say "with primitive matter" that you don't mean
> "**only** with primitive matter", but rather "with primitive matter +
> computation" - which is in effect a dualistic assumption.
Actually, once we assume some primitive matter, we are immediately
confronted with what Jacques Mallah called (in this list) the
implementation problem (also treated by Putnam and Chalmers). It is
even made worse with quantum computations. There is a sense to say
that the quantum vacuum implements all computations, and there is a
real difficulty in relating particular computation and particular
piece matter, and that is a prerequisite to attach mind to matter for
a partisan of PM+CTM.
> Again,
> please don't misunderstand me - I regard comp as a coherent *monistic*
> approach to both mind and matter that seeks to 'eliminate' neither,
> and which brings the mind-body issues into full focus. But the
> assumption of PM *in addition* would transform it into a type of
> epiphenomenal dualism.
Well I think that the addition of PM to CTM leads to contradiction or
elimination of consciousness (not a reduction of consciousness to
physical activity, but real elimination). What Peter seems to have
some difficulty to understand or admit.
Now, with a theory which assumes that CTM is false, you can coherently
define an identity thesis matter-mind (with enough actual infinities
on both sides), and defend some epiphenomenal dualism. With CTM
epiphenomenalism, for *primitive* matter, does not work.
>> The notion of computation does not rely on anything physical.
>
> OK, with the caveats above.
And there is nothing metaphysical here, just a tremendous mathematical
discovery made by Emil Post, the first, and rediscovered by Kleene,
Turing, Markov and some others. (To be frank, I don't believe Church
ever makes that discovery. It is really Kleene who realized that
Church "definition" was a really a thesis. But since Kleene introduced
the vocable "Church's thesis", mathematical logicians are using it.
Many call it "Church-Turing thesis" nowadays. But historically it is
either Emil Post who made the discovery the first, or perhaps Babbage,
who, when getting old, invented a language to describe his machine,
and discovered that the language was already an universal beast as
clever as his machine).
>
>> I think that what remains unclear in step seven is due to the lack of
>> knowledge of that "purely mathematical" notion of computation. You
>> need it to justify why Universal Machine and Universal Dovetailer"
>> exist and in what sense they are truly universal.
>
> Point taken. I will try to learn.
It is very kind to tell me, and to provide me with supplementary
motivations. I am a bit slow down by some amount of work to finish in
August. I give you the time to catch up, but I think I have to make
some summary, and I don't know how to do with Kim and Marty. Johnathan
told me that silence means assent, but in math, it is not always the
case. You can tell the math teacher, that your silence is assent,
during the course, but not during the exams, for example :)
Bruno
http://iridia.ulb.ac.be/~marchal/
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Received on Thu Aug 20 2009 - 16:54:03 PDT