Le 22-août-06, à 13:45, 1Z a écrit :

>
>
> Bruno Marchal wrote:
>> Le 21-août-06, à 16:01, 1Z a écrit :
>>
>>> Exactly. And if non-phsyical systems (Plato' Heaven) don't
>>> implement counterfactuals, then they can't run programmes,
>>> and if Plato's heaven can't run programmes, it can't be running us as
>>> programmes.
>>
>> I would say that only non-physical system implement counterfactuals.
>
> A counterfactual is somethingthat could have happened, but didn't.
> A static, immaterial systems can only handle counterfactuals by
> turning them into factuals -- everything that can happen does
> happen. It can fully capture the *conditional* structure of a
> programme,
> (unlike a "recording") at the expense of not being a process.
>
> A programme is not the same thing as a process.





I agree. Like a corpse is not the same as a life.








>
> Computationalism refers to real, physical processes running on material
> computers.


Words like "real", "physical" "material" needs to be (re)defined or at 
least clarify in front of the UDA.



> 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.


I would say there is no relevant difference, from the first person 
point of view, between a process in a "real universe" and a relative 
computation in Platonia.



>
> To exist Platonically is to exist eternally and necessarily. There is
> no time or changein Plato's heave.


All partial recursive solutions of Schroedinger or Dirac equation 
exists in Platonia, and define through that "block description" notion 
of internal time quite analogous to Everett subjective probabilities.




>  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. 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 suitabale
> 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.


A program is basically the same as a number. A process or a computation 
is a finite or infinite sequence of numbers (possibly branching, and 
defined relatively to a universal numbers).
The UD build all such (branching) sequences.




>
> No-one would believe that a brain-scan, however detailed, is conscious,


Of course.





> 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!


Of course.



>
> 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 soemthing already in Plato's heaven).


OK then.





> This
> route loses the conditonal structure, the counterfactuals that are
> vital to computer programmes and therefore to computationalism.


Not in the "all computations" view.




>
> 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.


The UD generates all such branching sequences. And the non triviality 
of computer science gives reasons to add different relative weigh on 
the branches (already like the MWI).




>
> 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.


Right.



>
> (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).


OK (but not quite relevant imo, because I can attribute a mind to a 
sleeping person, although it lacks inputs and outputs).



>
>
>
>> That counterfactuality is the essence of (immaterial) comp. Although
>> here Russell has a point: the quantum multiverse seems to handle
>> counterfactual.
>
> Multiverse theories seek to turn the 3rd-person "X could have happened
> but didn't"
> into the 1st-person "X could have been observed by me, but wasn't".


OK.



>
>>  Now if comp is correct, I cannot distinguish a
>> "genuine" quantum multiverse from any of its emulation in Platonia,
>
> A quantum multiverse is sitll only a tiny corner of Platonia.


A priori. But if the quantum hypothesis is correct, and if comp is 
correct, the multiverse is a point of view related to the *whole* of 
the arithmetical platonia.



>
> Physical many-world theories have resources to keep counterfactuals
> unobserved that immaterial MW-theories lack (including the simple
> of one that many mathematical possibilities do not
> exist physically).


?



>
> For instance, even if their are two informationally identical me's
> in different branches of a phsycial universe, it is not
> inevitable that any sharing or corss-over of
> consicousness would occur, because in  a phsyical
> universe, cosnciousness would have something other
> than informational structures to supervene on.
>
> Thus me might
> well be able to tell that we are in a quantum multiverse rather than
> Platonia, on the basis that we just do not observe enough weirdness.


Well, that is almost exactly the point of the UDA. Comp is testable by 
comparing the weight on the branches with the weight on the empirically 
infered branches.



>
> Too broad: If I am just a mathematical structure, I should have a much
> wider range of experience than I do. There is a mathemtical structure
> corresponding to myself with all my experiences up to time T. There is
> a vast array of mathematical structures corresponding to other versions
> of me with having a huge range of experiences -- ordinary ones, like
> continuing to type, extraordinary ones like seeing my computer sudenly
> turn into bowl of petunias. All these versions of me share the memories
> of the "me" who is writing this, so they all identify themselves as me.
> Remember, that for mathematical monism it is only necessary that a
> possible experience has a mathematical description. This is known as
> the White Rabbit problem. If we think in terms of multiverse theories,
> we would say that there is one "me" in this universe and other "me's"
> in other universes,a nd they are kept out of contact with each other.
> The question is whether a purely mathematical scheme has enough
> resources to impose isolation or otherwise remove the White Rabbit
> problem.


All right. And at first sight there will be too many white rabbits. But 
then, by linking the 1-comp indeterminacy with the "indexical" godelian 
form of incompleteness in the manner of the lobian interview, we see 
that computer science apparently has the resource to enhance local 
"normality". Even Gaussian one. That's my whole point indeed.




>
> Too narrow: there are a number of prima-facie phenomena which a purely
> mathematical approach struggles to deal with.
>
> space
> time
> consciousness
> causality
> necessity/contingency


You say so.





> Why space ? It is tempting to think that if a number of, or some other
> mathematical entity, occurs in a set with other numbers, that is, as it
> were, a "space" which is disconnected from other sets, so that a set
> forms a natural model of an *isolated* universe withing a multiverse, a
> universe which does not suffer from the White Rabbit problem. However,
> maths per se does not work that way. The number "2" that appears in the
> set of even numbers is exactly the same number "2" that appears in the
> list of numbers less than 10. It does not acquire any further
> characteristics from its context.


I agree. Any isolate mathematical structure would no more explain 
"space-consciousness" than a single real physical universe. The first 
person is distributed in all mathematical structure sufficiently rich 
to support the corresponding version of the 3-person. Any stable first 
person experience have to take into account that distribution.



> The time issue should be obvious. Mathematics is tradionally held to
> deal with timeless, eternal truths. This is reflected in the metpahor
> of mathematical truth being discovered not found (which, in line with
> my criticism of Platonism, should not be taken to seriously). It could
> be objected that physics can model time mathematically; it can be
> objected right back that it does so by spatialising time, by turning it
> into just another dimension, in which nothing really changes, and
> nothing passes. Some even go so far as to insist that this model is
> what time "really" is, which is surely a case of mistaking the map for
> the territory.


All right. I don't have that problem in the sense that comp indeed will 
identify some "map" with some "territory". It is one thing to be 
cautious not confusing map and territory, and another thing to pretend 
map are always everywhere different from a territory. By Brouwer fixed 
point theorem everybody knows that a map embedded continuously *in* a 
territory will have a fixed point where the point on the map is 
identical with the "point" in the territory. This is an image, but this 
is exactly what happens in all the fixed point theorem of computer 
science. Saying "yes" to a doctor is already possible only through 
accepting that an "artificial brain" will preserve the "real thing" 
(you).



>
> Consciousness is a problem for all forms of materialism and physicalism
> to some extent, but it is possible to discern where the problem is
> particularly acute. There is no great problem with the idea that matter
> considered as a bare substrate can have mental properities.


Panpsychism ? An electron would be conscious? Why do you think there 
are neurons in brains?
Why do you think there are genes in cells? Do you think they are only 
amplifiers of particle's mind.
Note that this would not a priori contradict comp per se, it would only 
make the substitution level very low.  (Unlikely imo, but that is not 
relevant for our discussion).




> Any
> inability to have mental properties would itself be a property and
> therefore be inconsistent with the bareness of a bare substrate. The
> "subjectivity" of conscious states, often treated as "inherent" boils
> down to a problem of communicating one's qualia -- how one feels, how
> things seem. Thus it is not truly inherent but depends on the means of
> communication being used. Feelings and seemings can be more readily
> communicated in artistic, poetic language, and least readily in
> scientific, technical language. Since the harder, more technical a
> science is, the more mathematical it is, the communication problem is
> at its most acute in a purely mathematical langauge. Thus the problem
> with physicalism is not its posit of matter (as a bare substrate) but
> its other posit, that all properties are physical. Since physics is
> mathematical, that amounts to the claim that all properties are
> mathematical (or at least mathematically describable). In making the
> transition from a physicalist world-view to a mathematical one, the
> concept of a material substrate is abandoned (although it was never a
> problem for consciousness) and the posit of mathematical properties
> becomes, which is a problem for consciousness becomes extreme.


Why?



>
> The interesting thing is that these two problems can be used to solve
> each other to some extent. if we allow extra-mathemtical properties
> into our universe, we can use them to solve the White Rabbit problem.
> There are two ways of doing this: We can claim either:-
>
> White Rabbit universes don't exist at all
> White Rabbit universes are causally separated from us (or remote in
> space)
> The first is basically a reversion to a single-universe theory (1).
> Mathematical monists sometimes complain that they can't see what role
> matter plays. One way of seeing its role is as a solution to the WR
> problem. For the non-Platonist, most mathematical entitites have a
> "merely abstract" existence. Only a subset truly, conceretely, exist.
> There is an extra factor that the priveleged few have. What is it ?
> Materiality. For the physicalist, matter is the token of existence.
> Maerial things, exist, immaterial ones don't.


"material things exist" is Aristotle's assumption.
I don't do that assumption, if only because it posits what I want to 
understand.
The UDA just explains why such an explanation is necessary once we 
assume comp.

> The second moves on from a Mathematical Multiverse to a physical one
> (3). The interesting thing about the second variety of
> non-just-mathematical monism is that as well as addressing the White
> Rabbit problem, it removes some further contingency. If the matter,
> physical laws, and so on, are logically possible, then the general
> approach of arguing for a universe/multiverse on the grounds of
> removing contingency must embrace them -- otherwise it would be a
> contingent fact that the universe/multiverse consists of nothing but
> mathematics.


OK.



>
>
>
>
>> and
>> the physical laws must take that into account.
>
> All forms of physics handle counterfactuals.
>
> Or do you mean it handles them in the sense of making them real  -- as
> Deutsch insists.


That way, except I say this from the comp assumption, unlike Deutsch 
who says this from the quantum assumption. (of course "real" means here 
generated by the UD)



>
>
> Multiverse theories claim that all possible worlds exist; but
> "possible" has more than one meaning, so there is more than one
> multiverse theory.


Sure. I got a different "multiverse" for each hypostases. But only few 
hypostases can correspond to a probability calculus (or a credibility 
calculus) on possible computations as seen from internal views. 
Limiting the range of multiverse corresponding to physical realities.




> Logical possibility simply means that something is
> not self-contradictory. Physical possibility means something is not
> contradictory to the laws of physics. "Five-sided square" is
> self-contradictory. "Water runnig uphill" is not, but it is physically
> impossoble.
>
> 'And, as I argued in FoR, the reality of universes in which we chose
> differently makes sense of (some) formally 'counter- factual'
> statements that don't make sense in single- universe physics, which can
> only help in making sense of free will.
> We are forced to conclude that, in spacetime physics [i.e. without a
> multiverse], conditional statements whose premise is false ("if Faraday
> had died in 1830 ...") have no meaning. '[Fabric of Reality, D Deutsch,
> p. 275]
>
>
>
> Suppose we agree. What is Deutsch himself to make of the
> counterfactuals we need to discuss the consequences of the laws of
> physics themselves, such as: "If charge were not conserved, the world
> would be a very different place"? The multiverse is no help, for by
> definition, it contains no worlds in which the laws are different.


Yes. It is a weak point of the quantum multiverse. Instead, the comp 
multiverse is unique by emerging on all arithmetical relations. I could 
say on all mathematical structures, but comp makes arithmetic enough.



> Deutsch's view thus implies that these essential claims about how
> things would have been had the laws of nature been different "have no
> meaning".

Not necessarily. Deutsch does endows AR. If a multiverse can exist 
without lobian machine inside (that exists!), then even for Deutsch 
some mathematical multiverse can be used to reason on physical 
counterfactuals. This could be not interesting by making the notion of 
counterfactuals too large, but that is another question.


> The moral is that if we want to give truth conditions for
> counterfactuals in terms of possible worlds, we need the set of all
> ogically possible worlds, not the set of physically possible worlds.

Yes.


> Indeed, Deutsch's whole multiverse probably counts as a single possible
> world in David Lewis's account, to which Deutsch later compares his own
> view: "The fruitfulness of the multiverse theory in contributing to the
> solution of long-standing philosophical problems is so great that it
> would be worth adopting even if there were no physical evidence for it
> at all. Indeed, the philosopher David Lewis, in his book On The
> Plurality of Worlds, has postulated the existence of a multiverse for
> philosophical reasons alone." [pp. 339,40], my italics. Note that it is
> doubtful whether the italicised counterfactual is itself meaningful, on
> Deutsch's view! In fact, what Lewis postulates is not a multiverse
> theory, in Deutsch's sense.

OK. (with the proviso above)


> from:-
> http://www.usyd.edu.au/time/price/preprints/DeutschReview-bjps.html
> Under David's interpretation, conditional statements whose antecedents
> are false in all physically possible universes, such "as there is a
> perpetual motion machine..." are meaningless.

Same as above. Note that with comp this problem is solved (but then the 
physical multiverse structure must be derived from the numbers laws).


>
> So are positive statements about things that don't exist in any
> physical universe, eg "there is a perpetual motion machine"
>
> So are negative statements about things that don't exist in any
> physical universe, "there is no perpetual motion machine". But, of
> course, we would regard the last as meaningful and true.
>
> There is in fact a whole bunch of reasons for thinking that statements
> don't require real-world referents to be meaningful.

Key remarks. Comp extends this to consciousness experience in all its 
shapes. Like in platonic dreams ultimate referent are not needed.


> We judge the
> meanings of statements by their semantic and syntactic makeup. we don't
> judge them by peeping into the universe next door. We can make sense of
> "there is life on other planets" without knowing whether there is in
> fact life on other planets. If we couldn't make (linguistic,
> comceptual) sense of "there is life on other planets", we wouldn't know
> how to go about verifying its truth.
>
> The kind of linguistic/semantic meaning I have been talking about is
> called "sense", as opposed to reference, the real-world object a
> statement is about, if it is about one. The distinction originated with
> the Frege


But that makes sense only through an aristotelian account of matter.



>
> David's contention seems to be based on the idea that "all meaning is
> reference". However it is arbitrary at best. It suggests statements
> like "if MWI is false.." are meaningless unless there is a world where
> MWI is in fact false. But how can that be if there is in fact, more
> than one world ?

I think we agree. I think you are just skeptical about the idea that 
standard comp entails pythagorean comp (not by making "matter" 
inconsistent, but by making any link between mind and "primitive 
matter" ad hoc and un-exploitable for solving the mind/body relation).

Bruno



http://iridia.ulb.ac.be/~marchal/


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