2009/9/13 Brent Meeker <meekerdb.domain.name.hidden>:
> You regard "doing the same computation" as a purely formal (=
> non-physical) critereon, but I think this is specious. It seems right
> because we talk about "a computation" at a very high level of
> abstraction. But when we ask what makes this causal sequence or that
> process a "computation", in contrast to other sequences or processes
> that aren't, we find that we must describe the computation as having an
> effect in the larger physical context. So to say that two physical
> processes realize the same computation is formal, but it is not *only*
> formal. It is implicitly physical too.
Yes, of course I know it's *implicitly* physical, that's the problem.
The point is that evaluating CTM as a physical theory of mind
necessitates making the relation between experience and process
*explicitly* physical, and actually attempting this inevitably results
in a failure to discover any consistent association between specific
physics and specific experience. This is not merely unfortunate, it
is a direct consequence of the arbitrariness of physical
implementation central to the hypothesis.
Your point about having an effect in the larger context is
unproblematic as long as it is considered from a third person
perspective. From this perspective there's no difficulty about the
physics of the realisation, since what is relevant is simply that it
fulfil the formal criteria in terms of *some* physical implementation,
no putative experiential aspect being at issue. I agree that this is
the right criterion to discriminate physical computational systems of
interest from those that are inconsequential (i.e. rocks etc.). The
point at issue with Peter, however, relates to the putatively
homogeneous experiential correlate of the heterogeneous physical
implementations, not their status as purely physical processes. We
seem to be discussing two different issues.
Consider what motivates CTM in the first place. The mind-body problem
seems in many ways as impenetrable as ever, despite all advances in
brain science and on the wider theoretical and experimental front.
But wait a moment, we have a nice theory of computation, and we know
how to apply it to computers and their programming. We even indulge
in metaphor about the thoughts and intentions of our devices (I know I
do). Maybe that's what the mind is? Wizard wheeze! But wait again
- when we actually think about what these beasties are up to
physically in their various realisations - mechanical, hydraulic,
electronic, pneumatic - there's a whole raft of promiscuous,
uncorrelated physical processes going on down there, and none of them
much like our own wetware version. How can we get a consistent
physics of consciousness out of this? What to do? I know - it
doesn't matter!
Great physical theory, eh?
David
>
> David Nyman wrote:
>> 2009/9/11 Flammarion <peterdjones.domain.name.hidden>:
>>
>>
>>>> I'm not sure I see what distinction you're making. If as you say the
>>>> realisation of computation in a physical system doesn't cause
>>>> consciousness, that would entail that no physically-realised
>>>> computation could be identical to any mental state.
>>>>
>>> That doesn't follow because causation and identity are different
>>> The realisation could be consciousness (fire IS combustion)
>>> without causing it (fire CAUSES smoke but it not smoke)
>>>
>>
>> So what did you mean the reader to conclude from your original
>> argument? You concluded that the realisation of a computation doesn't
>> cause consciousness. But did you also mean to imply that nonetheless
>> the realisation of a computation IS consciousness? If so, why didn't
>> you say so? And how would that now influence your evaluation of CTM?
>>
>>
>>>> This is what
>>>> follows if one accepts the argument from MGA or Olympia that
>>>> consciousness does not attach to physical states qua computatio.
>>>>
>>>>
>>> I find them both quite contestable
>>>
>>
>> If you would risk saying precisely why, you might have a counter-argument.
>>
>>
>>>> I agree. Nonetheless, when two states are functionally equivalent one
>>>> can still say what it is about them that is physically relevant. For
>>>> example, in driving from A to B it is functionally irrelevant to my
>>>> experience whether my car is fuelled by petrol or diesel. But there
>>>> is no ambiguity about the physical details of my car trip or precisely
>>>> how either fuel contributes to this effect.
>>>>
>>> One can say what it is about physical systems that explains
>>> its ability to realise a certain computation. One can't say that
>>> there is anything that makes it exclusively able to. Equally
>>> one can explain various ways of getting from A to B, but
>>> one can't argue that there is only one possible way.
>>>
>>
>> The point at issue is not whether there is only one way to realise a
>> computation, or to get from A to B. The point is that in the case of
>> the journey, the transition from physical irrelevance to relevance is
>> at the point where the physical result emerges as identical - i.e. as
>> the same journey form A to B. In the case of the computation, no such
>> physical identity of result ever emerges; all you have is a collection
>> of heterogeneous physical processes, each merely *formally* identical
>> to a given computation. It is a further - and physically entirely ad
>> hoc - assumption that this heterogeneity of physical states is
>> homogeneous with a single experiential state.
>>
>>
>>>> Yes, I agree. But if we're after a physical theory, we also want to
>>>> be able to give in either case a clear physical account of their
>>>> apprehensiveness, which would include a physical justification of why
>>>> the fine-grained differences make no difference at the level of
>>>> experience.
>>>>
>>> THat would be because they make no computational difference,
>>> if CTM is correct.
>>>
>>
>> If all you have to offer is circular arguments we shall simply go
>> round in circles.
>>
>>
>>>> I can only suppose that complete arbitrariness would be a random
>>>> association between physical states and mental states. This is not
>>>> what is meant by arbitrary realisation. What is meant is that the
>>>> requirement that a physical system be deemed conscious purely in
>>>> virtue of its implementing a computation rules out no particular kind
>>>> of physical realisation. Consequently a theory of this type is
>>>> incapable of explicating general principles of physical-mental
>>>> association independent of its functional posit.
>>>>
>>> It isn't. Why is that a problem?
>>>
>>
>> The problem is that theories which aren't reducible to fundamental
>> physics don't warrant consideration as physical theories. This is
>> amply demonstrated by the fact that, when reduced to a physical
>> interpretation, CTM is in fact shown to entail gross implausibilities.
>>
>>
>>>> Yes, but the upshot is that CTM is reduced to the theory that
>>>> conscious states can be associated with material systems only in a
>>>> manner that ex hypothesi must obscure any prospect of a general
>>>> reduction of their detailed material causes, because any such causes
>>>> could only be specific to each realisation.
>>>>
>>> You can have as many material details as you like
>>> so long as they are relevant to explaining the computation.
>>>
>>> Maybe you are hung up on causes. CTM is really an identity theory--
>>> mental
>>> states are identified with functional states. It's not fire-causes-
>>> smoke causation.
>>>
>>
>> I'm fine with mental states being identified with functional states.
>> The problem is one functional state reduces to multiple physical
>> states. Hence CTM entails that one experiential state reduces to
>> multiple physical states, without being able to give any consistent
>> physical, as opposed to formal, criterion for such identity.
>
> You regard "doing the same computation" as a purely formal (=
> non-physical) critereon, but I think this is specious. It seems right
> because we talk about "a computation" at a very high level of
> abstraction. But when we ask what makes this causal sequence or that
> process a "computation", in contrast to other sequences or processes
> that aren't, we find that we must describe the computation as having an
> effect in the larger physical context. So to say that two physical
> processes realize the same computation is formal, but it is not *only*
> formal. It is implicitly physical too.
>
> Brent
>
> >
>
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Received on Mon Sep 14 2009 - 00:46:39 PDT