Re: Dreaming On

From: David Nyman <david.nyman.domain.name.hidden>
Date: Wed, 09 Sep 2009 01:39:14 +0100

2009/9/3 Flammarion <peterdjones.domain.name.hidden>:

Peter, thanks for posting your review of the state of the debate as it
relates to our topic; it was very helpful. My reading of it leads me
to suppose that you entertain similar doubts about CTM, and on broadly
the same grounds. For example:

> Consider the argument that computer programmes are too abstract to
> cause consciousness. Consider the counter-argument that a running
> computer programme is a physical process and therefore not abstract at
> all.
>
> 1. Computationalism in general associates that consciousness with a
> specific comptuer programme, programme C let's say.
> 2. Let us combine that with the further claim that programme C
> causes cosnciousness, somehow leveraging the physical causality of the
> hardware it is running on.
> 3. A corrolary of that is that running programme C will always
> cause the same effect.
> 4. Running a programme on hardware is a physical process with
> physical effects.
> 5. It is in the nature of causality that the same kind of cause
> produces the same kind of effects-- that is, causaliy attaches to
> types not tokens.
> 6. Running a programme on hardware will cause physical effects, and
> these will be determined by the kind of physical hardware. (Valve
> computers will generate heat, cogwheel computers will generate noise,
> etc).
> 7. Therefore, running programme C on different kinds of hardware
> will not produce a uniform effect as required by 1.
> 8. Programmes do not have a physical typology: they are not natural
> kinds. In that sense they are abstract. (Arguably, that is not as
> abstract as the square root of two, since they still have physical
> tokens. There may be more than one kind or level of abstraction).
> 9. Conclusion: even running programmes are not apt to cause
> consciousness. They are still too abstract.

What you say above seems pretty much in sympathy with the reductio
arguments based on arbitrariness of implementation. By contrast, you
outline what a physicalist approach might entail:

> Consciousness. might depend on specific properties of hardware, of
> matter. This does not imply parochialism, the attitude that denies
> consciousness to poor Mr Data just because he is made out of silicon,
> not protoplasm. We know our own brains are conscious; most of us
> intuit that rocks and dumb Chinese Rooms are not; all other cases are
> debatable.
>
> Of course all current research in AI is based on computation in one
> way or another. If the Searlian idea that consciousness is rooted in
> physics, strongly emergent, and non-computable is correct, then
> current AI can only achieve consciousness accidentally. A Searlian
> research project would understand how brains generate consciousness in
> the first place -- the aptly-named Hard Problem -- before moving onto
> possible artificial reproductions, which would have to have the right
> kind of physics and internal causal activity -- although not
> necessarily the same kind as humans.

As you say above "consciousness might depend on specific properties of
hardware, of matter". If so, this would demand an explicitly physical
theory of mind, and such a 'Searlian' project would consequently seek
to associate a specific phenomenal state with specific physical
events. But CTM is not engaged on such a project; in fact it entails
the opposite conclusion: i.e. by stipulating its type-token identities
purely functionally it requires that a homogeneous phenomenal state
must somehow be associated with a teeming plurality of heterogeneous
physical states.

Various arguments - Olympia, MGA, the Chinese Room etc. - seek to
expose the myriad physical implausibilities consequential on such
implementation independence. But the root of all this is that CTM
makes impossible at the outset any possibility of linking a phenomenal
state to any unique, fully-explicated physical reduction. If nothing
physical can in principle be ruled out as an explanation for
experience, no uniquely-justified physical explanation need - or in
practice could - be explicated. The detailed implausibilities
variously invoked all fall out of this.

So if a physical theory of mind is what is needed, CTM would seem to
fail even as a candidate because its arbitrariness with respect to
physical realisation renders it incapable of grounding consciousness
in any specific fundamental physical reduction. Indeed defences of
functionalism against its various critics never cite any physical
grounds for the plausibility of conscious supervenience on the
physical composition of, say, the Chinese room, but focus instead on
defending the functional relevance of various features of the
experimental setup. Hence, without an explicitly physical, as opposed
to functional, criterion for what counts as a 'physical' explanation,
it is hard to see how CTM is compatible with any intelligible notion
of materialism. Indeed, its success could only be in direct
opposition to the principles of materialist reductive theory. Isn't
that a reasonable conclusion?

David

>
>
>
> On 03 Sep, 01:26, David Nyman <david.ny....domain.name.hidden> wrote:
>> 2009/9/2 Flammarion <peterdjo....domain.name.hidden>:
>>
>>
>>
>> >> and is thus not any particular physical
>> >> object.  A specific physical implementation is a token of that
>> >> computational type, and is indeed a physical object, albeit one whose
>> >> physical details can be of any variety so long as they continue to
>> >> instantiate the relevant computational invariance.  Hence it is hard
>> >> to see how a specific (invariant) example of an experiential state
>> >> could be justified as being token-identical with all the different
>> >> physical implementations of a computation.
>>
>> > I was right.
>>
>> > A mental type can be associated with a computational
>> > type.
>>
>> > Any token of a mental type can be associated with a token
>> > of the corresponding computational type.
>>
>> But what difference is that supposed to make?  The type association is
>> implicit in what I was saying.  All you've said above is that it makes
>> no difference whether one talks in terms of the mental type or the
>> associated computational type because their equivalence is a posit of
>> CTM.  And whether it is plausible that the physical tokens so picked
>> out possess the causal efficacy presupposed by CTM is precisely what I
>> was questioning.
>
>
> question it then. what's the problem?
>
>> >> But even on this basis it still doesn't seem possible to establish any
>> >> consistent identity between the physical variety of the tokens thus
>> >> distinguished and a putatively unique experiential state.
>>
>> > The variety of the physical implementations is reduced by grouping
>> > them
>> > as  equivalent computational types. Computation is abstract.
>> > Abstraction is
>> > ignoring irrelevant details. Ignoring irrelevant details establishes a
>> > many-to-one relationship : many possible implementations of one mental
>> > state.
>>
>> Again, that's not an argument - you're just reciting the *assumptions*
>> of CTM, not arguing for their plausibility.
>
> you're not arguing against its plausibility
>
>> The justification of the
>> supposed irrelevance of particular physical details is that they are
>> required to be ignored for the supposed efficacy of the type-token
>> relation to be plausible.  That doesn't make it so.
>
> why not? we already know they can be ignored to establish
> computational
> equivalence.
>
>> >>  On the
>> >> contrary, any unbiased a priori prediction would be of experiential
>> >> variance on the basis of physical variance.
>>
>> > Yes. The substance of the CTM claim is that physical
>> > differences do not make  a mental difference unless they
>> > make a computational difference. That is to say, switching from
>> > one token of a type of computation to another cannot make
>> > a difference in mentation. That is not to be expected on an
>> > "unbiased" basis, just because it is a substantive claim.
>>
>> Yes it's precisely the claim whose plausibility I've been questioning.
>
> You haven't said anything specific about what is wrong with it at all.
>
>> > The variety of the physical implementations is reduced by grouping
>> > them
>> > as  equivalent computational types. Computation is abstract.
>> > Abstraction is
>> > ignoring irrelevant details. Ignoring irrelevant details establishes a
>> > many-to-one relationship : many possible implementations of one mental
>> > state.
>>
>> Yes thanks, this is indeed the hypothesis.  But simply recapitulating
>> the assumptions isn't exactly an uncommitted assessment of their
>> plausibility is it?
>
>
> Saying it is not necessarily correct is not a critique
>
>>That can only immunise it from criticism.  There
>> is no whiff in CTM of why it should be considered plausible on
>> physical grounds alone.
>
>
>> Hence counter arguments can legitimately
>> question the consistency of its claims as a physical theory in the
>> absence of its type-token presuppositions.
>
>  If you mean you can criticise the CTM as offering nothing specific
> to resolve the HP, you are correct. But I *thought* we were
> discussing the MG/Olympia style of argument, which purportedly
> still applies even if you restrict yourself to cognition and forget
> about experience/qualia.
> Are we?
>
>> Look, let me turn this round.  You've said before that you're not a
>> diehard partisan of CTM.  What in your view would be persuasive
>> grounds for doubting it?
>
> I'll explain below. But the claim I am interested in is that CTM
> somehow disproves materalism (Maudlin, BTW takes it the other way
> around--
> materialism disproves CTM). I have heard not a word in support of
> *that* claim.
>
>
> ust an Artificial Intellence be a Computer ?
>
> An AI is not necessarily a computer. Not everything is a computer or
> computer-emulable. It just needs to be artificial and intelligent! The
> extra ingredient a conscious system has need not be anything other
> than the physics (chemistry, biology) of its hardware -- there is no
> forced choice between ghosts and machines.
>
> A physical system can never be exactly emulated with different
> hardware -- the difference has to show up somewhere. It can be hidden
> by only dealing with a subset of a systems abilities relevant to the
> job in hand; a brass key can open a door as well as an iron key, but
> brass cannot be substituted for iron where magnetism is relevant.
> Physical differences can also be evaded by taking an abstract view of
> their functioning; two digital circuits might be considered equivalent
> at the "ones and zeros" level of description even though they
> physically work at different voltages.
>
> Thus computer-emulability is not a property of physical systems as
> such. Even if all physical laws are computable, that does not mean
> that any physical systems can be fully simulated. The reason is that
> the level of simulation matters. A simulated plane does not actually
> fly; a simulated game of chess really is chess. There seems to be a
> distinction between things like chess, which can survive being
> simulated at a higher level of abstraction, and planes, which can't.
> Moreover, it seems that chess-like things are in minority, and that
> they can be turned into an abstract programme and adequately simulated
> because they are already abstract.
>
> Consciousness. might depend on specific properties of hardware, of
> matter. This does not imply parochialism, the attitude that denies
> consciousness to poor Mr Data just because he is made out of silicon,
> not protoplasm. We know our own brains are conscious; most of us
> intuit that rocks and dumb Chinese Rooms are not; all other cases are
> debatable.
>
> Of course all current research in AI is based on computation in one
> way or another. If the Searlian idea that consciousness is rooted in
> physics, strongly emergent, and non-computable is correct, then
> current AI can only achieve consciousness accidentally. A Searlian
> research project would understand how brains generate consciousness in
> the first place -- the aptly-named Hard Problem -- before moving onto
> possible artificial reproductions, which would have to have the right
> kind of physics and internal causal activity -- although not
> necessarily the same kind as humans.
>
>    "When I say that the brain is a biological organ and consciousness
> a biological process, I do not, of course, say or imply that it would
> be impossible to produce an artificial brain out of nonbiological
> materials that could also cause and sustain consciousness...There is
> no reason, in principle, why we could not similarly make an artificial
> brain that causes consciousness. The point that needs to be empnasized
> is that any such artificial brain would have to duplicate the actual
> causes of human and animal brains to produce inner, qualitative,
> subjective states of consciousness. Just producing similar output
> behavior would not by itself be enough."
>
> [Searle, MLS, p. 53]
>
> "Is the Brain A Machine?"
> John Searle thinks so .
>
>    The brain is indeed a machine, an organic machine; and its
> processes, such as neuron firings, are organic machine processes.
>
> The Mystery of Consciousness. page 17: Is he right ? To give a
> typically philosophical answer, that depends on what you mean by
> 'machine'. If 'machine' means an artificial construct, then the answer
> is obviously 'no'. However. Searle also thinks the the body is a
> machine, by which he seems to mean that it has been understand in
> scientific terms, we can explain biology by in terms of to chemistry
> and chemistry in terms of physics. Is the brain a machine by this
> definition ? It is being granted that the job of he brain is to
> implement a conscious mind, just as the job of the stomach is to
> digest, the problem then is that although our 'mechanical'
> understanding of the stomach does allow us to understand digestion we
> do not, according to Searle himself, understand how the brain produces
> consciousness. He does think that the problem of consciousness is
> scientifically explicable, so yet another definition of 'machine' is
> needed, namely 'scientifically explained or scientifically explicable'
> -- with the brain being explicable rather than explained. The problem
> with this stretch-to-fit approach to the meaning of the word 'machine'
> is that every time the definition of brain is broadened, the claim is
> weakened, made less impactful.
>
> PDJ 03/02/03
> The Chinese Room
> The Chinese Room and Consciousness
> According to the proponents of Artificial Intelligence, a system is
> intelligent if it can convince a human interlocutor that it is. This
> is the famous Turing Test. It focuses on external behaviour and is
> mute about how that behaviour is produced. A rival idea is that of the
> Chinese Room, due to John Searle. Searle places himself in the room,
> manually executing a computer algorithm that implements intelligent-
> seeming behaviour, in this case getting questions written in Chinese
> and mechanically producing answers, without himself understanding
> Chinese. He thereby focuses attention on how the supposedly
> intelligent behaviour is produced. Although Searle's original idea was
> aimed at semantics, my variation is going to focus on consciousness.
> Likewise, although Searle's original specification has him
> implementing complex rules, I am going to take it that the Chinese
> Room is implemented as a conceptually simple system --for instance, a
> Giant Look-Up Table -- in line with the theorem of Computer Science
> which has it that any computer can be emulated by a Turing Machine.
>
> If you think a Chinese Room implemented with a simplistic, "dumb"
> algorithm can still be conscious, you are probably a behaviourist; you
> only care about that external stimuli get translated into the
> appropriate responses, not how this happens, let alone what it feels
> like to the system in question.
>
> If you think this dumb Chinese Room is not conscious, but a smart one
> would be, you need to explain why. There are two explanatory routes:
> one that says consciousness is inessential, and another that says that
> hardware counts as well as software.
>
> Any smart AI can be implemented as a dumb TM, so the more complex
> inner workings which supposedly implement consciousness , could be
> added or subtracted without making any detectable difference. Given
> the assumption that the computational differences are what matter,
> this would to add up to epiphenomenalism, the view that consciousness
> exists but is a bystander that doesn't cause anything, since there is
> not any computational difference between the simple implementation and
> the complex one.
>
> On the other hand, if it is assumed that epiphenomenalism if false,
> then it follows that implementational differences must matter, since
> the difference between the complex and the dumb systems is not in
> their computational properties. That in turn means computationalism is
> false. The Chinese Room argument then succeeds, but only as
> interpreted fairly strictly as an argument about the ability of
> algorithms to implement consciousness. Any actual computational
> systems, or artificial intelligence construct, will be more than just
> an algorithm; it will be the concrete implementation of an algorithm.
> Since it is the implementation that makes the difference between a
> fully successful AI and a "zombie" (functional enough to pass a Turing
> test, but lacking real consciousness), and since every AI would have
> some sort of implementation, the possibility of an actual systems
> being conscious is far from ruled out. The CR argument only shows that
> it is not conscious purely by virtue of implementing an algorithm. It
> is a succesful argument up to that point, the point that why AI may be
> possible, it will not be pruely due to running the right algorithm.
> While the success of an AI programme is not ruled out, it is not
> guaranteed either. It is not clear which implementations are the right
> ones. A system running the right algorithm on the wrong hardware may
> well be able to pass a Turing Test, but if the hardware is relevant to
> consciousness as well, a system with the wrong hardware will be an
> artificial zombie. It will be cognitively competent, but lacking in
> genuine phenomenal consciousness. (This is in line with the way robots
> and the like are often portrayed in science fiction. A further wrinkle
> is that an exact computational emulation of a real person -- a real
> person who believes in qualia anyway -- would assert its possession of
> qualia while quite possibly not possessing any qualia to boast about).
>
> Thus the success of the CR argument against a software-only approach
> to AI has the implication that the TT is not adequate to detect the
> success of a strong AI (artificial consciousness) project. (Of course,
> all this rests on beahviourism being false; if behaviourism is true
> there is no problem with a TT, since it is a test of behaviour). We
> need to peek inside the box; in order to know whether an AI device has
> full phenomenal, consciousness, we would need a successful theory
> linking consciousness to physics. Such a theory would be nothing less
> than an answer to the Hard Problem. So a further implication of the
> partial success of Searlian arguments is that we cannot bypass the
> problem of explaining consciousness by some research programme of
> building AIs. The HP is logically prior. Except for beahviourists.
>
> Peter D Jones 8/6/05
> Syntax and Semantics. The Circularity Argument as an Alternative
> Chinese Room
>
> The CR concludes that syntax, an abstract set of rules is insufficient
> for semantics. This conclusions is also needed as a premise for
> Searle's syllogistic argument
>
>   1. Syntax is not sufficient for semantics.
>   2. Computer programs are entirely defined by their formal, or
> syntactical, structure.
>   3. Minds have mental contents; specifically, they have semantic
> contents.
>   4. Therefore, No computer program by itself is sufficient to give a
> system a mind. Programs, in short, are not minds, and they are not by
> themselves sufficient for having minds.
>
> Premise 01 is the most contentious of the four. The Chinese Room
> Argument, which Searle puts forward to support itm is highly
> contentious. We will put forward a different argument to support it.
>
> An objection to the CR argument goes: "But there must be some kind of
> information processing structure that implements meaning in our heads.
> Surely that could be turned into rules for the operator of the Chinese
> Room".
>
> A response, the Circularity Argument goes: a system of syntactic
> process can only transform one symbol-string into another; it does not
> have the power to relate the symbols to anything outside the system.
> It is a circualr, closed system. However, to be meaningful a symbol
> must stand for something other than itself. (The Symbol must be
> Grounded). Therefore it must fail to have any real semantics.
>
> It is plausible that any given term can be given an abstract
> definition that doesn't depend on direct experience. A dictionary is
> collection of such definitions. It is much less plausible that every
> term can be defined that way. Such a system would be circular in the
> same way as:
>
> "present: gift"
>
> "gift: present"
>
> ...but on a larger scale.
>
> A dictionary relates words to each other on a static way. It does not
> directly have the power to relate words to anything outside itseld. We
> can understand dictionary definitons because we have already grapsed
> the meanings of some words. A better analogy for the Symbol Grounding
> problem is that of trying to learn an entirely unknown langauge for a
> dictionary. (I have switched from talking about syntacital
> manipluation processes to static dicitonaries; Searles arguments that
> syntax cannot lead to semantics have been critices for dealing with
> "syntax" considered as abstract rules, whereas the computational
> processes they are aimend are concrete, physcial and dynamic. The
> Circularity argument does not have that problem. Both abstract syntax
> and symbol-manipulation processed can be considered as circular).
>
> If the Circularity Argument, is correct, the practice of giving
> abstract definitions, like "equine quadruped" only works because
> somewhere in the chain of definitions are words that have been defined
> directly; direct reference has been merely deferred, not avoided
> altogether.
>
> The objection continues: "But the information processing structure in
> our heads has a concrete connection to the real world: so do AI's
> (although those of the Chinese Room are minimal). Call this is the
> Portability Assumption.
>
> But they are not the same concrete connections. The portability of
> abstract rules is guaranteed by the fact that they are abstract. But
> concrete causal connections are not-abstract. They are unlikely to be
> portable -- how can you explain colour to an alien whose senses do not
> include anything like vision?
>
> Copying the syntactic rules from one hardware platform to another will
> not copy the semantics. Therefore,semantics is more than syntax.
>
> If the Portability Assumption is correct, an AI (particularly a
> robotic one) could be expected to have some semantics, but there is no
> reason it should have human semantics. As Wittgenstein said: "if a
> lion could talk, we could not understand it".
>
> Peter D Jones 13/11/05
> The Chinese Room and Computability
> I casually remarked that mental behaviour 'may not be computable'.
> This will shock some AI proponents, for whom the Church-Turing thesis
> proves that everything is computable. More precisely, everything that
> is mathematically computable is computable by a relatively dumb
> computer, a Turing that something can be simulated doesn't mean the
> simulation has all the relevant properties of the original: flight
> simulators don't take off. Thirdly the mathematical sense of
> 'computable' doesn't fit well with the idea of computer-simulating
> fundamental physics. A real number is said to be mathematically
> computable if the algorithm that churns it out keeps on churning out
> extra digits of accuracy..indefinitely. Since such a algorithm will
> never finish churning out a single real number physical value, it is
> difficult to see how it could simulate an entire universe. Yes, I am
> assuming the universe is fundamentally made of real numbers. If it is,
> for instance finite, fundamental physics might be more readily
> computable, but the computability of physics still depends very much
> on physics and not just on computer science).
> The Systems Response and Emergence
> By far the most common response to the CR argument is that, while the
> room's operator, Searle himself, does not understand Chinese, the room
> as a whole does. According to one form of the objection, individual
> neurons do not understand Chinese either; but this is not a fair
> comparison. If you were to take a very simple brain and gradually add
> more neurons to it, the increase in information-processing capacity
> would keep in line with an increase in causal activity. However, the
> equivalent procedure of gradually beefing up a CR would bascially
> consist of adding more and more rules to the rule book while the
> single "neuron", the single causally active constituent, the operator
> of the room did all the work. It is hard to attribute understanding to
> a passive rulebook, and hard to attribute it to an operator performing
> simple rote actions. It is also hard to see how the whole can be more
> than the sum of the parts. It is very much a characteristic of a
> computer, or other mechanism, that there is no mysterious emegence
> going on; the behavour of the whole is always explicable in term sof
> the behaviour of the parts. There is no mystery, by contrast, in more
> neurons being able to do more work. Searle doesn't think you can put
> two dumbs together and get a smart. That is no barrier to putting 100
> billion dumbs together to get a smart. Or to putting two almost-smarts
> together to get a smart.
> The Chinese Room and Speed
> Of course, if we burden the room's operator with more and more rules,
> he will go slower and slower. Dennett thinks a slow chinese room would
> not count as conscious at all. Nature, he notes, requires conscious
> beings to react within a certain timescale in order to survive. That
> is true, but it does not suggest any absolute speed requirement.
> Nature accomodates the tortoise and the mayfly alike. The idea that a
> uselessly slow consciousness would not be actually be a concsiousness
> at all is also rather idiosyncratic. We generally credit a useless
> vestigal limb with being a loimb, at least.
>
> Anyway, Dennett's speed objection is designed to lead into one of his
> favourite ideas: the need for massive parallelism. One Searle might
> lack conscious semantics, but a million might do the trick. Or so he
> says. But what would parallelism bring us except speed?
> The Chinese Room and complexity.
> The Dennettians make two claims; that zombies are impossible, and that
> the problem with the Chinese room is that it is too simple. We will
> show that both claims cannot be true.
>
> What kind of complexity does the Chinese Room lack? By hypothesis it
> can pass a Turing test: it has that much complexity in the sense of
> outward performance. There is another way of thinking about
> complexity: complexity of implementation. . So would the Chinese Room
> be more convincing if it had a more complex algorithm? The problem
> here is that there is a well-founded principle of computer science
> according to which a computer programme of any complexity can emulated
> by a particular type of essentially simple machine called a Turing
> Machine. As it happens, the Chinese Room scenario matches a Turing
> Machine pretty well. A Turing Machine has a simple active element, the
> read-write head and a complex instruction table. In the Chinese Room
> the sole active element is the operator, performing instruction by
> rote; any further complexity is in the rulebooks. Since there is no
> stated limit to the "hardware" of the Chinese Room -- the size of the
> rulebook, the speed of the operator -- the CR could be modified to
> implement more complex algorithms without changing any of the
> essential features.
>
> Of course differences in implementation could make all sorts of non-
> computational differences. Dennett might think no amount of
> computation will make a flight simulator fly. He might think that the
> Chinese Room lack sensor and effectuators to interact with its
> environment, and that such interactions are needed to solve the symbol-
> grounding problem. He might think that implementational complexity,
> hardware over software is what makes the difference between real
> consciousness and zombiehood. And Searle might well agree with him on
> all those points: he may not be a computationalist, but he is a
> naturalist. The dichotomy is this: Denett's appeal to complexity is
> either based on software, in which case it is implausible, being
> undermined by Turing equivalence; or it is based in hardware, in which
> case it is no disproof of Searle. Rather, Searle's argument can be
> seen as a successful disproof of computationalism(ie the only-software-
> matters approach) and Dennett's theory of consciousness is a proposal
> for a non-computationalistic, hardware-based, robotic approach of the
> kind Searle favours.
>
> Some Denettians think a particular kind of hardware issue matters:
> parallelism. The Chinese room is "too simple" in that it is a serial
> processor. Parallel processors cannot in fact computer anything --
> cannot solve any problem -- that single processors can't. So parallel
> processing is a difference in implementation, not computation. What
> parallel-processing hardware can do that serial hardware cannot is
> perform opertations simultaneously. Whatever "extra factor" is added
> by genuine simultaneity is not computational. Presumably that means it
> would not show up in a Turing test -- it would be indetectable from
> the outside. So the extra factor added by simultaneity is something
> that works just like phenomenality. It is indescernable from the
> outside, and it is capable of going missing while external
> functionality is preserved. (We could switch a parallel processor off
> during a TT and replace it with a computationally equivalent serial
> one. According to the parallel processing claim, any genuine
> cosnciousness would vanish, although the external examiner preforming
> the TT would be none the wiser). In short, simulateneity implies
> zombies.
> The Chinese Room and Abstraction
> Consider the argument that computer programmes are too abstract to
> cause consciousness. Consider the counter-argument that a running
> computer programme is a physical process and therefore not abstract at
> all.
>
>   1. Computationalism in general associates that consciousness with a
> specific comptuer programme, programme C let's say.
>   2. Let us combine that with the further claim that programme C
> causes cosnciousness, somehow leveraging the physical causality of the
> hardware it is running on.
>   3. A corrolary of that is that running programme C will always
> cause the same effect.
>   4. Running a programme on hardware is a physical process with
> physical effects.
>   5. It is in the nature of causality that the same kind of cause
> produces the same kind of effects-- that is, causaliy attaches to
> types not tokens.
>   6. Running a programme on hardware will cause physical effects, and
> these will be determined by the kind of physical hardware. (Valve
> computers will generate heat, cogwheel computers will generate noise,
> etc).
>   7. Therefore, running programme C on different kinds of hardware
> will not produce a uniform effect as required by 1.
>   8. Programmes do not have a physical typology: they are not natural
> kinds. In that sense they are abstract. (Arguably, that is not as
> abstract as the square root of two, since they still have physical
> tokens. There may be more than one kind or level of abstraction).
>   9. Conclusion: even running programmes are not apt to cause
> consciousness. They are still too abstract.
>
> Computational Zombies
> This argument explores the consequenes of two assumptions:
>
>   1. We agree that Searle is right in his claim that software alone
> is not able to bring about genuine intelligence,
>   2. But continue to insist that AI research should nonetheless be
> pursued with computers.
>
> In other words, we expect the success or failure of our AI to be
> dependent on the choice of software in combination with the choice of
> hardware.
>
> The external behaviour of a computational system -- software and
> hardware taken together -- is basically detemined by the software it
> is running; that is to say, while running a programme on different
> hardware will make some kind of external differences, they tend to be
> irrelevant and uninteresting differences such as the amount of heat
> and noise generated. Behaviourstic tests like the Turing Test are
> specifically designed to filter out such differences (so that the
> examiner's prejudices about what kind of system could be conscious are
> excluded). The questions and responses in a TT are just the inputs and
> outputs of the software.
>
> Abandoning the software-only approach for a combined software-and-
> hardware approach has a peculiar consequence: that it is entirely
> possible that out of two identically programmed systems running on
> different hardware, one will be genuinely intelligent (or have genuine
> consciousness, or genuine semantic comprehension, etc) and the other
> will not. Yet, as we have seen above, these differences will be --
> must be -- indiscernable in a Turing Test. Thus, if hardware is
> involved in the implementation of AI in computers, the Turing Test
> must be unreliable. There is a high probability that it will give
> "false positives", telling us that unconscious AIs are actually
> conscious -- a probability that rises with the number of different
> systems tested.
>
> To expand on the last point: suppose you get a positive TT result for
> one system, A. Then suppose you duplicate the software onto a whole
> bunch of different hardware platforms, B, C, D....
>
> (Obviously, they are all assumed to be capable of running the software
> in the first place). They must give the same results to the TT for A,
> since they all run the same software, and since the software
> determines the responses to a TT, as we established above, they must
> give positive results. But eventually you will hit the wrong hardware
> -- it would be too unlikely to always hit on the right hardware by
> sheer chance, like throwing an endless series of heads. When you do
> hit the wrong hardware, you get a false positive. (Actually you don't
> know you got a true positive with A in the first place...)
>
> Thus, some AIs would be "zombies" in a restricted sense of "zombie".
> Whereas a zombie is normally thought of a physical duplicate lacking
> consciousness, these are software duplicates lacking appropriate
> hardware.
>
> This peculiar sitation comes about because of the separability of
> software and hardware in a computational approach, and the further
> separation of relevant and irrelvant behaviour in the Turing Test.
> (The separability of software simply means the ability to run the same
> software on differenet hardware). Physical systems in general -- non
> computers, not susceptible to separate descriptions of hardware and
> software -- do not have that separability. Their total behaviour is
> determined by their total physical makeup. A kind of Articial
> Intelligence that was basically non-computational would not be subject
> to the Compuational Zombie problem. Searle is therefore correct to
> maintain, as he does, that AI is broadly possible.
> Neuron-silicon replacement scenarios
> Chalmers claims that replacing neurons with silicon will preserve
> qualia so long as it preserves function -- by which he means not just
> outward, behavioural function but also the internal organisation that
> produces it. Obviously, he has to make that stipulation because it is
> possible to think of cases, such as Searle's Chinese Room, where
> outward behaviour is generated by a very simplistic mechanism, such as
> a lookup table. In fact, if one takes the idea that consciousness
> supervenes on the functional to the extreme, it becomes practically
> tautologous. The most fine-grained possible functional description
> just is a physical description (assuming physics does not deliver
> intrinsic properties, only structural/behavioural ones) , and the
> mental supervenes in some sense on the physical, so consciousness can
> hardly fail to supervene on an ultimately fine-grained functional
> simulation. So the interesting question is what happens between these
> two extremes at, say, the neuronal level.
>
> One could imagine a variation of the thought-experiment where one's
> brain is first replaced at the fine-grained level, and the replaced
> again with a coarser-grained version, and so, on, finishing in a Giant
> Look Up Table. Since hardly anyone thinks a GLUT would have phenomenal
> properties, phenomenality would presumably fade out. So there is no
> rigid rule that phenomenality is preserved where functionality is
> preserved.
>
> It is natural suppose that one's functional dispositions are in line
> with one's qualia. One claims to see red because one is actually
> seeing red. But an intuition that is founded on naturalness cannot be
> readily carried across to the very unnaturual situation of having
> one's brain gradually replaced.
>
> What is it like to have one's qualia fade away ? If one had ever been
> a qualiaphile, one would continue to claim to have qualia, without
> actually doing so. That is, one would be under an increasing series of
> delusions. It is not difficult to imagine thought-experiments where
> the victim's true beliefs are changed into false ones. For instance,
> the Mad Scientist could transport the victim from their bedroom to a
> "Truman Show" replica while they slept. Thus the victim's belief that
> they were still in their own bedroom would be falsified. Since beliefs
> refer to states-of-afairs outside the head, you don't even need to
> change anything about someone's psychology to change the truth of
> their beliefs. So there is no great problem with the idea that
> rummaging in someone's head does change their beliefs -- any such
> process must change beliefs relating to what is physically inside the
> victims head. Since the victim is funtionally identical, they must
> carry on believing they have neural tissue in their head, even after
> it has all been replaced. It doesn't follow from this that replacing a
> brain with silicon must destroy qualia, but there is definitely a
> precedent for having false beliefs about one's own qualia after one's
> brain has been tampered with.
>
> A GLUT of Turings
> An old programmer's trick is to store "potted" results rather than
> calculating them afresh each time. This saves tiem at the expense of
> using up memory. Earlier, we used the idea of a "Giant Look-Up Table"
> to implement, in an essentially dumb way, the whole of an extremely
> coplicated system, such as a human brain.
>
> Can a (Giant) Look-Up Table emulate any Turing Machine (and therefore,
> any computer, and therefore, if computationalism is true, any brain).
>
> The usual objection to LUT's is that they are stateless. But that is
> easy get round. Add a timestamp as an additional input.
>
> Or includde with the fresh input each time a record of all previous
> conversations it has had, with the total table size limiting the
> "lifespan" of the machine
>
> The feedback of the old conversation gives the machine a state memory,
> very straightforwardly is voluminously encoded
>
> What is the LUT for a sorting algorithm?
>
> It is a table which matches lists of unsorted numbers against sorted
> numbers. it doesn't even need to be stateful. And, yes, if it is
> finite it will only sort lists of up to some size limit. But then any
> algorithm has to run for a finite length of time, and will not be able
> to sort some lists in the time allowed. So time limits are just being
> traded for space limits.
>
> If you want to pass a Turing test with a glut, you only need a coarse-
> grained (but still huge) GLUT, that matches verbal resonses to verbal
> inputs. (A GLUT that always produced the same response to the same
> query would be quickly detected as a machine, so it would need the
> statefullness trick, making it even larger...). However, it is
> counterinutitive that such a GLUT would simulate thought since nothing
> goes on between stimulus and response. Well, it is counterintuitive
> that any GLUT would think or feel anything. Daryl McCullough and Dave
> Chalmers chew the issue over in this extract from a Newsgroup
> discussion.
> Computationalism
> Computationalism is the claim that the human mind is essentially a
> computer. It can be picturesquely expressed in the "yes, doctor"
> hypothesis -- the idea that, faced with a terminal disease, you would
> consent to having your consciousness downloaded to a computer.
>
> There are two ambiguities in "computationalism" -- consciousness vs.
> cognition, process vs programme -- leading to a total of four possible
> meanings.
>
> Most people would not say "yes doctor" to a process that recorded
> their brain on a tape a left it in a filing cabinet. Yet, that is all
> you can get out of the timeless world of Plato's heaven (programme vs
> process).
>
> That intuition is, I think, rather stronger than the intuition that
> Maudlin's argument relies on: that consciousness supervenes only on
> brain activity, not on counterfactuals.
>
> But the other ambiguity in computationalism offers another way out. If
> only cognition supervenes on computational (and hence counterfactual)
> activity, then consciousness could supervene on non-counterfactual
> activity -- i.e they could both supervene on physical processes, but
> in different ways.
> Aritifical intelligence and emotion
> AI enthusiasts are much taken with the analogy between the brain's
> (electro) chemical activity and the electrical nature of most current
> computers. But brains are not entirely electrical. Neurons sit in a
> bath of chemicals which effects their behaviour, too. Adrenaline, sex
> hormones, recreational drugs all affect the brain. Why are AI
> proponents so unconcerned about brain chemistry? Is it because they
> are so enamoured with the electrical analogy? Or because they just
> aren't that interested in emotion?
> Platonic computationalism -- are computers numbers?
> Any computer programme (in a particular computer) is a long sequence
> of 1's and 0's, and therefore, a long number. According to Platonism,
> numbers exist immaterially in "Plato's Heaven". If programmes are
> numbers, does that mean Plato's heaven is populated with computer
> programmes?
>
> The problem, as we shall see is the "in a a particular computer"
> clause.
>
> As Bruno Marchal states the claim in a more formal language:
>
> "Of course I can [identify programmes with numbers ]. This is a key
> point, and it is not obvious. But I can, and the main reason is Church
> Thesis (CT). Fix any universal machine, then, by CT, all partial
> computable function can be arranged in a recursively enumerable list
> F1, F2, F3, F4, F5, etc. "
>
> Of course you can count or enumerate machines or algorithms, i.e.
> attach unique numerical labels to them. The problem is in your "Fix
> any universal machine". Given a string of 1's and 0s wihouta universal
> machine, and you have no idea of which algorithm (non-universal
> machine) it is. Two things are only identical if they have all*their
> properties in common (Leibniz's law). But none of the propeties of the
> "machine" are detectable in the number itself.
>
> (You can also count the even numbers off against the odd numbers , but
> that hardly means that even numbers are identical to odd numbers!)
>
> "In computer science, a fixed universal machine plays the role of a
> coordinate system in geometry. That's all. With Church Thesis, we
> don't even have to name the particular universal machine, it could be
> a universal cellular automaton (like the game of life), or Python,
> Robinson Aritmetic, Matiyasevich Diophantine universal polynomial,
> Java, ... rational complex unitary matrices, universal recursive group
> or ring, billiard ball, whatever."
>
> Ye-e-es. But if all this is taking place in Platonia, the only thing
> it can be is a number. But that number can't be associated with a
> computaiton by another machine, or you get infinite regress.
> Is the computationalist claim trivial -- are all systems computers?
> It can be argued that any physical theory involving real numbers poses
> problems (and all major theories do, at the time of writing). Known
> physics is held to be computable, but that statement needs to be
> qualified in various ways. A number thinking particularly of a real
> number, one with an infinite number of digits -- is said to be
> computable if a Turing machine will continue to spit out digits
> endlessly. In other words, there is no question of getting to the
> "last digit". But this sits uncomfortably with the idea of simulating
> physics in real time (or any plausible kind of time). Known physical
> laws (including those of quantum mechanics) are very much infused with
> real numbers and continua.
>
>    "So ordinary computational descriptions do not have a cardinality
> of states and state space trajectories hat is sufficient for them to
> map onto ordinary mathematical descriptions of natural systems. Thus,
> from the point of view of strict mathematical description, the thesis
> that everything is a computing system in this second sense cannot be
> supported"
>
> Moreover, the universe seems to be able decide on their values on a
> moment-by-moment basis. As Richard Feynman put it: "It always bothers
> me that, according to the laws as we understand them today, it takes a
> computing machine an infinite number of logical operations to figure
> out what goes on in no matter how tiny a region of space, and no
> matter how tiny a region of time. How can all that be going on in that
> tiny space? Why should it take an infinite amount of logic to figure
> out what one tiny piece of space/time is going to do?
>
> However, he went on to say:
>
> So I have often made the hypotheses that ultimately physics will not
> require a mathematical statement, that in the end the machinery will
> be revealed, and the laws will turn out to be simple, like the chequer
> board with all its apparent complexities. But this speculation is of
> the same nature as those other people make I like it, I dont like it,
> and it is not good to be prejudiced about these things".
> Is no physical system a computer, except in the eye of the beholder
> Comsider the claim that "computation" may not correctly be ascribed to
> the physics per se. Maybe it can be ascribed as an heuristic device as
> physical explanation has an algorithmic component as Wolfram suggests.
>
> Whether everything physical is computational or whether specific
> physical systems are computational are two quite different questions.
> As far as I can see, a NAND's gate being a NAND gate is just as
> objective as a square thing's being square.
>
> Are the computations themselves part of the purely physical story of
> what is going on inside a compter?
>
> Seen mathematically, they have to be part of the physical story. They
> are not some non-physical aura hanging over it. A computer doing
> something semantic like word-processing needs external interpretation
> in the way anything semantic does: there is nothing intrinsic and
> objective about a mark that makes it a sign standing for something.
> But that is down to semantics, not computation. Whilst we don't expect
> the sign "dog" to be understood universally, we regard mathematics as
> a universal language, so we put things like
>
> | || ||| ||||
>
>
> on space probes, expecting them to be understood. But an entity that
> can understand a basic numeric sequence could understand a basic
> mathematical function. So taking our best guesses about
> intersubjective comprehensibility to stand for objectivity,
> mathematical computation is objective.
> Is hypercomoutation a testable hypothesis? We can decide between non-
> computable physics (CM) and computable physics (QM). What the question
> hinges on is the different kinds and levels of proof used in emprical
> science and maths/logic.
> Is Reality real ? Nick Bostrom's Simulation Argument
> The Simulation Argument seeks to show that it is not just possible
> that we are living inside a simulation, but likely.
>
> 1 You cannot simulate a world of X complexity inside a world of X
> complexity.(quart-into-a-pint-pot-problem).
>
> 02 Therefore, if we are in a simulation the 'real' world outside the
> simulation is much more complex and quite possibly completely
> different to the simulated world.
>
> 3 In which case, we cannot make sound inferences from the world we are
> appear to be in to alleged real world in which the simulation is
> running
>
> 04 Therefore we cannot appeal to an argumentative apparatus of advanced
> races, simulations etc, since all those concepts are derived from the
> world as we see it -- which, by hypothesis is a mere simulation.
>
> 05 Therefore, the simulation argument pulls the metaphysical rug from
> under its epistemological feet.
>
> The counterargument does not show that we are not living in a
> simulation, but if we are , we have no way of knowing whether it is
> likely or not. Even if it seems likely that we will go on to create
> (sub) simulations, that does not mean we are living in a simulation
> that is likely for the same reasons, since our simulation might be
> rare and peculiar. In particular, it might have the peculiarity that
> sub-simulations are easy to create in it. For all we know our
> simulators had extreme difficulty in creating our universe. In this
> case, the fact that it is easy to create sub simulations within our
> (supposed) simulation, does not mean it is easy to creae simulations
> per se.
> Computational counterfactuals, and the Computational-Platonic Argument
> for Immaterial Minds
> For one, there is the argument that: A computer programme is just a
> long number, a string of 1's and 0's.
> (All) numbers exist Platonically (according to Platonism)
> Therefore, all programmes exist Platonically.
>
> A mind is special kind of programme (According to computaionalism)
> All programmes exist Platonically (previous argument)
> Therefore, all possible minds exist Platonically
> Therefore, a physical universe is unnecessary -- our minds exist
> already in the Platonic realm
>
> The argument has a number of problems even allowing the assumptions of
> Platonism, and computationalism.
>
> A programme is not the same thing as a process.
>
> Computationalism refers to real, physical processes running on
> material computers. Proponents of the argument need to show that the
> causality and dynamism are inessential (that there is no relevant
> difference between process and programme) before you can have
> consciousness implemented Platonically.
>
> To exist Platonically is to exist eternally and necessarily. There is
> no time or change in Plato's heave. Therefore, to "gain entry", a
> computational mind will have to be translated from a running process
> into something static and acausal.
>
> One route is to replace the process with a programme. let's call this
> the Programme approach.. After all, the programme does specify all the
> possible counterfactual behaviour, and it is basically a string of 1's
> and 0's, and therefore a suitable occupant of Plato's heaven. But a
> specification of counterfactual behaviour is not actual counterfactual
> behaviour. The information is the same, but they are not the same
> thing.
>
> No-one would believe that a brain-scan, however detailed, is
> conscious, so not computationalist, however ardent, is required to
> believe that a progamme on a disk, gathering dust on a shelf, is
> sentient, however good a piece of AI code it may be!
>
> Another route is "record" the actual behaviour, under some
> circumstances of a process, into a stream of data (ultimately, a
> string of numbers, and therefore something already in Plato's heaven).
> Let's call this the Movie approach. This route loses the conditional
> structure, the counterfactuals that are vital to computer programmes
> and therefore to computationalism.
>
> Computer programmes contain conditional (if-then) statements. A given
> run of the programme will in general not explore every branch. yet the
> unexplored branches are part of the programme. A branch of an if-then
> statement that is not executed on a particular run of a programme will
> constitute a counterfactual, a situation that could have happened but
> didn't. Without counterfactuals you cannot tell which programme
> (algorithm) a process is implementing because two algorithms could
> have the same execution path but different unexecuted branches.
>
> Since a "recording" is not computation as such, the computationalist
> need not attribute mentality to it -- it need not have a mind of its
> own, any more than the characters in a movie.
>
> (Another way of looking at this is via the Turing Test; a mere
> recording would never pass a TT since it has no condiitonal/
> counterfactual behaviour and therfore cannot answer unexpected
> questions).
>
> A third approach is make a movie of all possible computational
> histories, and not just one. Let's call thsi the Many-Movie approach.
>
> In this case a computation would have to be associated with all
> related branches in order to bring all the counterfactuals (or rather
> conditionals) into a single computation.
>
> (IOW treating branches individually would fall back into the problems
> of the Movie approach)
>
> If a computation is associated with all branches, consciousness will
> also be according to computationalism. That will bring on a White
> Rabbit problem with a vengeance.
>
> However, it is not that computation cannot be associated with
> counterfactuals in single-universe theories -- in the form of
> unrealised possibilities, dispositions and so on. If consciousness
> supervenes on computation , then it supervenes on such counterfactuals
> too; this amounts to the response to Maudlin's argument in wihch the
> physicalist abandons the claim that consciousness supervenes on
> activity.
>
> Of ocurse, unactualised possibilities in a single universe are never
> going to lead to any White Rabbits!
> Turing and Other Machines
> Turing machines are the classical model of computation, but it is
> doubtful whether they are the best model for human (or other organic)
> intelligence. Turing machines take a fixed input, take as much time as
> necessary to calculate a result, and produce a perfect result (in some
> cases, they will carry on refining a result forever). Biological
> survival is all about coming up with good-enough answers to a tight
> timescale. Mistaking a shadow for a sabre-tooth tiger is a msitake,
> but it is more accpetable than standing stock still calculating the
> perfect interpretation of your visual information, only to ge eaten.
> This doesn't put natural cognition beyone the bounds of computation,
> but it does mean that the Turing Machine is not the ideal model.
> Biological systems are more like real time systems, which have to
> "keep up" with external events, at the expense of doing some things
> imprefectly.
> Quantum and Classical Computers
> (Regarding David Deutsch's FoR)
> To simulate a general quantum system with a classical computer you
> need a number of bits that scales exponentially with the number of
> qubits in the system. For a universal quantum computer the number of
> qubits needed to simulate a system scales linearly with the number of
> qubits in the system. So simulating quantum systems classically is
> intractable, simulating quantum systems with a universal quantum
> computer is tractable.
> Time and Causality in Physics and Computation
> The sum total of all the positions of particles of matter specififies
> a (classical) physical state, but not how the state evolves. Thus it
> seems that the universe cannot be built out of 0-width (in temporal
> terms) slices alone. Physics needs to appeal to something else.
>
> There is one dualistic and two monistic solutions to this.
>
> The dualistic solution is that the universe consists (separately) of
> states+the laws of universe. It is like a computer, where the data
> (state) evolves according to the programme (laws).
>
> One of the monistic solutions is to put more information into states.
> Physics has an age old "cheat" of "instantaneous velocities". This
> gives more information about how the state will evolve. But the state
> is no longer 0-width, it is infinitessimal.
>
> Another example of states-without-laws is Julian Barbour's Platonia.
> Full Newtonian mechanics cannot be recovered from his "Machian"
> approach, but he thinks that what is lost (universes with overall
> rotation and movement) is no loss.
>
> The other dualistic solution is the opposite of the second: laws-
> without-states. For instance, Stephen Hawking's No Boundary Conditions
> proposal
>
> Maudlin's Argument and Counterfactuals
> We have already mentioned a parallel with computation. There is also
> relevance to Tim Maudlin's claim that computationalism is incompatible
> with physicalism. His argument hinges on serparating the activity of a
> comptuaitonal system from its causal dispositions. Consciousness, says
> Maudlin supervened on activity alone. Parts of an AI mechansim that
> are not triggered into activity can be disabled without changing
> consciousness. However, such disabling changes the computation being
> performed, because programmes contain if-then statements only one
> branch of which can be executed at a time. The other branch is a
> "counterfactual", as situation that could have happened but didn't.
> Nonetheless, these counterfactuals are part of the algorithm. If
> changing the algorithm doesn't change the conscious state (because it
> only supervenes on the active parts of the process, not the unrealised
> counterfactuals), consciousness does not supervene on computation.
>
> However, If causal dispositions are inextricably part of a physical
> state, you can't separate activity from counterfactuals. Maudlin's
> argument would then have to rely on disabling counterfactuals of a
> specifically computational sort.
>
> We earlier stated that the dualistic solution is like the separation
> between programme and data in a (conventional) computer programme.
> However, AI-type programmes are typified by the fact that there is not
> a barrier between code and programme -- AI software is self-modifying,
> so it is its own data. Just as it is not physically necessary that
> there is a clear distinction between states and laws (and thus a
> separability of physical counterfactuals), so it isn't necessarily the
> case that there is a clear distinciton between programme and data, and
> thus a separability of computational counterfactuals. PDJ 19/8/06
> Chalmers on GLUTS
> Daryl McCullough writes:
>
>    I made the split to satisfy *you*, Dave. In our discussion about
> the table lookup program, your main argument against the table lookup
> being conscious was the "lack of richness" of its thinking process.
> And this lack of richness was revealed by the fact that it took zero
> time to "think" about its inputs before it made its outputs. So I have
> patched up this discrepancy by allowing "silent" transitions where
> there is thinking, but no inputs. However, as I thought my example
> showed, this silent, internal thinking can be perfectly trivial; as
> simple as counting. It is therefore not clear to me in what sense
> there can be more "richness" in some FSA's than there is in a table
> lookup.
>
> Dave Chalmers writes:
>
>    I made it abundantly clear that the problem with the lookup table
> is not the mere lack of silent transitions -- see my response to your
> message about the brain that beeps upon every step. Rather, the
> objection is that (a) a lot of conscious experience goes on between
> any two statements I make in a conversation; and (b) it's very
> implausible that a single state-transition could be responsible for
> all that conscious experience.
>
>    Like the beeping brain, ordinary FSAs with null inputs and outputs
> aren't vulnerable to this argument, as in those cases the richness of
> such conscious experience need not result from a single state-
> transition, but from a combination of many.
>
> DM:
>
>    If you allow a "null input" to be a possible input, then the
> humongous table lookup program becomes functionally equivalent to a
> human brain. To see this, note that the states of the table lookup
> program are essentially sequences of inputs [i_1,i_2,i_3,...,i_n]. We
> use the mapping M([]) = the initial state, M([i_1,i_2, ..., i_n,i_{n
> +1}]) = I(M([i_1,i_2, ..., i_n]),i_{n+1}). The output for state
> [i_1,i_2, ..., i_n] is whatever the lookup table has for that sequence
> of inputs, which is correct by the assumption that the table lookup
> program gets the behavior right.
>
> DC:
>
>    You made essentially this argument before, and I responded in a
> message of Feb 28. Here's the relevant material:
>
>    Your complaint about clocks, that they don't support
> counterfactuals, is I think, easily corrected: for example, consider a
> machine M with a state determined by a pair: the time, and the list of
> all inputs ever made (with the times they were made). If
> "implementation" simply means the existence of a mapping from the
> physical system to the FSA, then it seems that such a system M would
> simultaneously implement *every* FSA. Counterfactuals would be
> covered, too.
>
>    This is an interesting example, which also came up in an e-mail
> discussion recently. One trouble with the way you've phrased it is
> that it doesn't support outputs (our FSAs have outputs as well as
> inputs, potentially throughout their operation); but this can be fixed
> by the usual "humongous lookup table" method. So what's to stop us
> saying that a humongous lookup table doesn't implement any FSA to
> which it's I/O equivalent? (You can think of the table as the
> "unrolled" FSA, with new branches being created for each input. To map
> FSA states to (big disjunctions of) table states, simply take the
> image of any FSA state under the unrolling process.) This is a tricky
> question. Perhaps the best answer is that it really doesn't have the
> right state-transitional structure, as it can be in a given state
> without producing the right output and transiting into the appropriate
> next state, namely when it's at the end of the table. Of course this
> won't work for the implementation of halting FSAs (i.e. ones that must
> halt eventually, for any inputs, but one could argue that the FSA
> which describes a human at a given time isn't a halting FSA (the human
> itself might be halting, but that's because of extraneous influences
> on the FSA). Your example above doesn't have the problem at the end of
> the table; it just goes on building up its inputs forever, but at cost
> of being able to produce the right outputs.
>
>    Not that I don't think lookup-tables pose some problems for
> functionalism -- see my long response to Calvin Ostrum. But in any
> case this is far from Putnam's pan-implementationalism.
>
> DM:
>
>    The conclusion, whether you have silent transitions or not, is
> that functional equivalence doesn't impose any significant constraints
> on a system above and beyond those imposed by behavioral equivalence.
>
> DC:
>
>    Even if your argument above were valid, this certainly wouldn't
> follow -- the requirement that a system contains a humongous lookup
> table is certainly a significant constraint! I also note that you've
> made no response to my observation that your original example, even
> with the silent transitions, is vastly constrained, about as
> constrained as we'd expect an implementation to be.
>
> >
>

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Received on Wed Sep 09 2009 - 01:39:14 PDT

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