2009/9/14 Brent Meeker <meekerdb.domain.name.hidden>:
>> 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.
>
> That seems like a category mistake. You're asking for and explicitly physical relation
> between a computation and a physical process. But a computation isn't physical; the
> relation has to relate something non-physical to the physical - so obviously it relates
> the non-physical things like potential action in a context or evolutionary function to the
> physical process.
>
>>This is not merely unfortunate, it
>> is a direct consequence of the arbitrariness of physical
>> implementation central to the hypothesis.
>
> I don't see the problem. There are arbitrarily many computations of the same function too.
I'm having a really hard time comprehending why we're at such
cross-purposes here. I have no difficulty with the formal definition
of a computation, its multiple realisations, or with your criterion of
relevance to an external context. However none of this is remotely
relevant to what's at issue with respect to the status of CTM as a
physical theory of *phenomenal experience*, as opposed to observed
*behaviour*, which AFAICS is all you are referring to above.
Let me put it like this. In any physical account of a particular
phenomenon, some physical events will be relevant, and some
irrelevant. I gave the example of differently fuelled journeys - I'm
sure you can think of a dozen equally good or better examples. In any
of these examples you would seek - and should at least in principle be
able - to explain what is physically directly relevant to the outcome,
what is irrelevant (in the sense of merely generally supportive of)
the outcome, and how precisely this demarcation is justified in
explicit physical terms. In each case, the line of demarcation would
be at the point where some common physical outcome can be identified
as emerging from disparate underlying processes
Now let's consider CTM on the same terms. We seek to explain an
outcome - an experience - that will emerge at some point of
demarcation of relevant and irrelevant physical processes. To this
end let us attempt to test the postulates of CTM against physical
criteria independent of the hypothesis. In fact we have no way of
demarcating any homogeneous physical emergents other than at the
boundaries of the system, because the hypothesis rules this out, so
already this makes the case quite dissimilar to any other, but let
this pass for the moment. We will consider only the putative
homogeneous experiential correlate of the heterogeneous physical
computational processes. What can we employ as the physical criteria
for its emergence? That the relevant physical processes should be
present. What can we use to identify such processes and establish
their relevance in terms of any given realisation? Answer: only the
formal premises of CTM. Anything else? Not a thing.
Computational theory in purely behavioural guise meets the criterion
of equivalence not through homogeneity of physical realisation but in
consistency of relation with an environment, as you imply. By
contrast, any internal physical processes associated with a
computational theory of homogeneous experience can only be identified
and justified in terms of its own formal internal premises. Hence any
physical justification deployed for this purpose in terms of any
specific realisation must be completely circular. We are not supposed
to assume our conclusions in our premises, and the inevitable result
of so doing is to fail to make any substantive physical commitments
independent of the formal presuppositions of the hypothesis itself.
It is entirely a consequence of this that reductios such as MGA are
able to do their work, because this physical vacuity is what permits
grossly implausible realisations to be considered valid by the posits
of the theory. This is QED AFAICS. How specifically, and at what
point of the argument, would you disagree?
David
>
> David Nyman wrote:
>> 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.
>
> That seems like a category mistake. You're asking for and explicitly physical relation
> between a computation and a physical process. But a computation isn't physical; the
> relation has to relate something non-physical to the physical - so obviously it relates
> the non-physical things like potential action in a context or evolutionary function to the
> physical process.
>
>>This is not merely unfortunate, it
>> is a direct consequence of the arbitrariness of physical
>> implementation central to the hypothesis.
>
> I don't see the problem. There are arbitrarily many computations of the same function too.
>
> Brent
>
>>
>> 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 - 02:46:43 PDT