Hi Hal,
Thank you very much for you work in writing this review and commentary
of the Maulding paper. I have not read it yet, but would like to ask some
questions and interject some comments, even if I end up looking like a fool.
;-)
Interleaving
----- Original Message -----
From: ""Hal Finney"" <hal.domain.name.hidden>
To: <everything-list.domain.name.hidden>
Sent: Sunday, August 07, 2005 4:20 PM
Subject: Maudlin's Machine and the UDist
> Rutgers philosopher Tim Maudlin has a paper intended to challenge certain
> views about consciousness and computation, which we have discussed
> occasionally on this list. It is called "Computation and Consciousness",
> Journal of Philosophy v86, pp. 407-432. I have temporarily put a copy
> online at http://www.finney.org/~hal/maudlin.pdf . This is a personal
> copy and I would ask you not to redistribute it.
[SPK]
It is sad that copyrights are what they have become such that the free
flow and accessibility of papers is becoming more and more like the guilds
of yore. :_(
>
> The background question is when a given physical system can be said
> to implement a given computation (especially, a conscious computation).
> We imagine that the computation is specified in abstract terms, perhaps as
> a program in a conventional computer language, or perhaps in a lower-level
> form as a program for a Turing Machine or some other model of computation.
> But it is abstract. We then ask, given a certain physical system P,
> is it implementing computation C?
[SPK]
This seems to touch on the question that Chalmers asked here:
http://consc.net/papers/rock.html
>
> In practice, it seems that this is an easy question to answer.
> Our computers implement the programs which are fed into them. No one
> denies that.
>
> But philosophers have argued that there is a way of viewing the activity
> of a physical system that can make it appear to be implementing *any*
> computation C. We can think of C as passing through a series of states:
> C1, C2, C3, and so on. And we can think of the physical system P as
> passing through a series of states: P1, P2, P3. So if we map P1 to C1,
> P2 to C2, and so on, we can argue that P is implementing C, for any C
> and for pretty much any P.
[SPK]
It seems to me that there should be nothing special about the ordering
of the P_i for the COMP assumptions to hold, OTOH, there seems to be some
requirement that some aspect of P_n be relatable to P_n-1 in a way that is
independent of how the particular P_i are extent, no?
>
> The philosophers' response to this is that it is not enough to be able to
> set up such a mapping. What is also necessary, to claim that P implements
> (or "instantiates") C, is that the *counterfactuals* would have to
> exist in correspondence as well. That is, not only the states C1, C2,
> C3 but also other states of C that would have been taken if the inputs
> had been different, have to have correspondences in P. It is claimed
> that the kind of arbitrary mapping described above will not work once
> counterfactuals are taken into account. (I'm not sure I fully understand
> or agree with this rebuttal but it is well accepted in the field.)
[SPK]
The contrafactuals have been shown, at least in QM experiements, to be
just as *real* when it comes to notion of causation as the factuals. So if
we are to take empirical evidence as a guide, it seems that there is some
reason to expect that contrafactuals can not be dismissed out of hand.
http://www.nonlocal.com/quantum-d/v2/kbowden_03-15-97.html
>
> The principle that whether P implements C depends on these counterfactuals
> is one of the issues that Maudlin addresses. When referring to conscious
> computations, this principle is generally considered part of the
> "computationalist" hypothesis, that the instantiation of an appropriate
> computation C in a physical system P actually produces a corresponding
> sensation of consciousness. Implicit in this hypothesis is that to be
> said to be instantiating C, P must have had enough structure to also
> produce counterfactuals, if they had occured.
>
> Well, that's a lot of background! And there's more. The other thesis
> that Maudlin considers is called supervenience, a philosophical word for
> what is fortunately a pretty straightforward concept. It is that whether
> a physical system implements a given computation depends solely on the
> activity of that physical system. No mystical or non-physical elements
> or attributes need to be considered in judging whether P implements C.
> All that matters is P's physical activity.
[SPK]
We can hope that no "obscurum per occultum" is involved! ;-)
>
> In a nutshell, Maudlin argues that these two common views on the
> matter are actually in contradiction. But frankly, although Maudlin's
> argument is complicated and involves all kinds of thought experiments and
> elaborate, imaginary machines, I think it is actually quite an obvious
> point. Supervenience means that implementation depends on what P does,
> while support for counterfactuals means that implementation depends on
> what P doesn't do. Q.E.D.! Maudlin merely takes great time and care
> to illustrate the contradiction in detail.
>
> Another place that counterfactuals come into play is when considering
> whether replays are conscious. If we re-run a calculation, but this
> time we don't include the logic aspects but merely passively replay a
> recording of each component's activity, is this conscious? Does this
> P instantiate C? The answer, according to the counterfactual view, is
> no, because a mere replay of a recorded set of events does not include
> counterfactuals and will not work right if a different input is supplied.
> On the other hand if the re-run is a genuine computation which merely
> happens to be given the same input and hence to follow the same sequence
> of operations, then that re-run would in fact be considered to generate
> the consciousness.
[SPK]
Is it Live or Memorex? What is the difference between object and
Representation?
>
> Now to bring in the multiverse perspective, in the flavor I have been
> pursuing. From the viewpoint that says that all information objects
> exist and are distributed according to the Universal Distribution (UDist),
> what can we say about these questions?
>
> First, the question of whether a physical system P implements a
> computation C is seen to be the wrong question to ask. C is an
> information object and has a measure. Likewise, although we think
> of P as physical, in the UDist model the universe containing P is
> merely one information object, and P is a subset of that universe.
> The question is therefore, how much measure does P contribute to C?
> That will depend on the measure of P and on how much of P's measure can
> be seen as contributing to C.
[SPK]
I am still worried about how a measure can exist over a set, collecton,
class, or whatever of computations! Does not the notion of a measure require
the existence of a space where each point is an object of the class and the
measure itself defines the similarity/difference between one object, here a
computation, and some given other?
What ontological status does "Computation Space" have?
>
> Now, here I need to address an ambiguity in some of the philosophical
> discussion of this issue, which shows up in Maudlin's paper among other
> places. What do we mean by an abstract computation? Is it a program,
> or is it a run of a program (i.e. the sequence of states it goes through,
> also called the "trace")?
[SPK]
I personally make a big deal about a difference between a program and
the running of a program! The former is merely an ontic question and the
latter involves some supervinient "process" that implements the program, no?
>
> Well, I suppose it could mean either one; from the UDist perspective,
> both views can be supported. As information objects, we can distinguish
> programs and program traces, just as we could distinguish theorems and
> proofs, or numbers and sequences. They are related but not the same.
> We could ask for the measure of a program, and define it by representing
> the program in some canonical form like Java source code, then finding
> the shortest program that would output that program. Or we could ask
> for the measure of a program trace, define it as a sequence of states
> again in some canonical form, and ask for the shortest program that
> would output that sequence.
>
> Maudlin talks about programs as sequences of states, which provides
> for the most direct way of thinking of them as causing or creating
> consciousness. I'll do it that way, too. So when I speak of P or C
> here I am talking about sequences of states, not static structures
> like machine descriptions or source code listings.
>
> The specific mechanism in the UDist framework for calculating the
> contribution of P to C's measure is to imagine a program which takes
> P as input and produces C as output. Both P and C are considered as
> information objects for this purpose. Such a program can be quite small
> for the case where our common sense would say that P does implement C.
> We can find a mapping of P into C that is simple and straightforward,
> and therefore corresponds to a small program.
>
> On the other hand in cases where common sense would say that P does
> nothing to implement C, such as where P is a clock and C is a conscious
> program, any such mapping from P to C is going to have to be about as
> big as C itself. P is of no help in calculating such a C and hence
> there is no short program that produces C given P.
[SPK]
Could it be that a "clock" (the physical object) IS, in fact, the
shortest program that implements "what it is like to be a clock" - the
program?
>
> There is no need to consider counterfactuals in this framework. What
> keeps a clock from contributing measure to arbitrary programs is not its
> failure to implement counterfactuals, it is the fact that no short program
> can use the structure of a clock to output an arbitrary computation C.
>
> This analysis also produces a different answer than the traditional
> approach for considering the impact of replays. Both "passive" replays
> (which just play back a recorded sequence of states) and "active" ones
> (which re-do a computational sequence) would both add roughly equal
> amounts to measure, because both would allow for similarly short programs
> which turn the sequence of P states to the sequence of C states.
>
> Turning to Maudlin's paper, his main effort is to construct a machine
> (named Olympia) which essentially does a passive replay but which contains
> triggers which will turn on an "active" machine if the inputs are not
> what were recorded during the replay. In this way he argues that the
> machine does implement counterfactuals. However when run in replay mode,
> none of the counterfactual machinery gets activated, because in practice
> the inputs are all given the correct values. And his machine is so
> simple in how it does the replay that the actual physical activity is
> almost non-existent. In this way he argues that the supervenience thesis
> would find insufficient activity for consciousness, in contradiction to
> the computationalist principle.
[SPK]
This seems to support my ill-formed argument that there is a huge and
important difference between the existence of some Interger N and the
computation of N; again the former merely "exists" the latter requires a
process...
Additionally, I hope that Mauldin assumes that some kind of "activity",
re: process, is involved in consciousness. From your depiction I assume that
he does, but will have to hold back until I read the paper.
This is a very important point, IMHO, because it is distinguishing
between the actual implentation of a conscious mind and a sequence of "snap
shots" of the brain assumed to exist a priori.
>
> I'm not sure I find Maudlin's argument persuasive even within the standard
> framework, for a variety of reasons, but I won't go into that here.
[SPK]
I would really like to read your thoughts on this!
> My goal is to analyze it within the UDist framework. In that case the
> paradox or contradiction doesn't arise, because the only question is
> the degree to which the structure of Maudlin's machine Olympia allows
> for a short program that maps to the computational pattern C. We can
> first ignore the extra machinery for handling counterfactuals since
> that is not an issue in the UDist approach. For the rest, Maudlin
> rearranges the program states and includes in Olympia a map from every
> program state to some other program state, which will be an enormous map
> for any actual conscious experience. I suspect that the size of this
> additional structure, and the way the states have been scrambled, will
> complicate the program that has to do the translation somewhat, but that
> it will still be possible to output C using a reasonably short program.
> Therefore I would expect that his machine might not contribute quite
> as much to the measure of C as a conventional machine would, but still
> would contribute an appreciable measure.
>
> In any case, his machine certainly does not pose a challenge or paradox
> for the UDist framework, since UDist is merely a recipe for how to
> calculate a number, the measure of C. All kinds of bizarre machines
> might be imagined which would in some way relate to C, and still in
> principle we could estimate out how much measure they would each add to C.
> It seems that no paradox can arise from this type of analysis.
>
> Hal Finney
[SPK]
I do hope that there is more to UD than Scholastic speculations. ;-)
Onward,
Stephen
Received on Mon Aug 08 2005 - 01:43:06 PDT