On 09 May 2017, at 07:16, Bruce Kellett wrote:
On 9/05/2017 1:57 am, David Nyman wrote:
On 8 May 2017 8:21 a.m., "Bruce Kellett"
<bhkell...@optusnet.com.au> wrote:
On 8/05/2017 4:53 pm, David Nyman wrote:
Both Hoyle's pigeon holes and Barbour's time capsules assume that
there is a coherent underlying physics with regular exceptionless
laws. Until you have something like that, you cannot define
consistent continuations.
But I'm afraid that's implied by assumption unless one takes the
view that the evolution of physical states is fundamentally
incomputable,
But I thought that that was what Bruno claimed. If one assumes
physics in one's derivation, then the circularity is vicious.
Oh dear no, that's not right at all. What is uncomputable is any
extrinsically conceived *extraction* of physics from the
computational Babel consequent on the theory. There is no possible
search function for this. That extraction then is necessarily a
complex consequence of observer selection. Post such extraction,
the evolution of physical states is then by assumption finitely
computable, modulo the FPI, else computationalism must fail as a
theory of mind or of physics. At this point the objective
situation, mutatis mutandis, is essentially equivalent to Everett's
relative state assumptions.
The other point on which I must take you to task is again the
question of circularity. It's not the job of computationalism's toy
model to explicate every detail of the extraction of physics,
although it's already the case that it *predicts* the multiple
continuations implicit in the wavefunction, which is more than can
be said for QM itself which merely retrodicts them (again modulo
the FPI). Given the conjunction of the assumption of
computationalism and our observation of the physical environment
described by QM, all the theory has to show at this stage is that
it is not incompatible with these data (as it would be if, say, the
evolution of the wavefunction itself were shown to be
uncomputable). It should further explicate some reasonably
convincing justification for why just such a physics might be
expected to underpin the effective environment we observe. But the
*facts* of our observation of such a physics are not at issue.
There is no relevant question of circularity to deal with here.
As to the so called Occam catastrophe, as exemplified in your
Boltzmann brain scenario, potential resolution necessarily can be
understood under computationalism only from a first person
perspective, as I previously suggested to you. We need to justify,
in terms of a subjective measure, why we should indeed expect the
physics we observe to emerge as the predominating computational
mechanism underlying our normally intelligible perceptions. To do
this we only need to show that "last Tuesday" computational
snippets can only reinforce, and magical or unintelligible ones
cannot interfere, with "normally intelligible" and complexly
connected continuations. A way to grasp this intuitively is in
terms of something like Hoyle's "amnesic multiple personality"
heuristic which, though as you say it was originally based on the
assumption of physics, IMO illustrates the relevant considerations
equally intuitively on computational assumptions. In any case, the
analogy of a multitasking OS that I also mentioned suffices equally
well in this regard.
From this perspective, no amount of white noise in continuations of
"Boltzmann" computations could make a substantive subjective
difference. The reason being that the consequence is
overwhelmingly likely to be a total subjective unintelligibility
which will plausibly tend to be utterly swamped, in the struggle of
forgetting and remembering, by "normally intelligible"
continuations. The FPI is, obviously, the relevant consideration in
this regard. This is what I meant when I said that an absence of
evidence for this sort of pathology or unintelligibility is not
evidence of its absence. It suffices that these out of phase
components of experience be swamped in the battle for what one
might term personal subjective emergence. They just typically get
forgotten far more frequently than they get remembered by Hoyle's
multiply solipsistic agent. Hence what we may think of as
pathological scenarios would be expected to be very poor and
haphazard candidates in the ongoing struggle for apparently
persistent, pervasive and lawful subjective emergence. What would
emerge with these characteristics would then be consistently
remembered histories underpinned by a robust and reiterative
physical mechanism whose highly selective observation by us would
then be the final evidence of its predomination in this epic
personal struggle.
I gave you an illustration a few days ago (on which you didn't
comment) of what one might term the "psycho-theological" aspect of
computationalism. I said that consciousness or first person
subjectivity was really a pointless cherry on the cake of physics
whose mechanism must be assumed to proceed without any a priori
need of such a baroque supernumerary assumption. Indeed it can only
be an a posteriori datum tacked on to the physical scheme of
things. Computationalism, by contrast, can only be understood in
the final analysis as a synthesis of all possible subjective
personal histories. "Point of view" is then just what prevents them
from all happening at once. Thus physics, under the same
assumptions, can in turn be understood finally as the successful
computational generator underlying the "dreams of the machines".
David
I find most of what you say here very much a matter of wishful
thinking, and not entirely consistent at that. Let me come at it in
a different way.
I find Barbour's idea of time capsules quite helpful here. Each time
capsule is a self-contained conscious moment. There is no
progression necessarily involved, so the computation that gives one
conscious moment is complete in itself, and independent of other
such conscious moments. (In Barbour's picture, these moments are
points in configuration space that are related physically, but we do
not use that aspect here.) In the moment, you are self-aware, and
aware of memories that give you a concept of self. But in that
moment there is no way that you can know whether these memories are
veridicial or not -- they could well all be completely false, in
which case there is no "you" that continues through time as a
related series of experiences. Each experienced moment is complete
in itself, and there is no continuation. If all you have is the
moment of consciousness, you can go no further than this. It is all
an illusion, and there is no physics to extract.
Of course, this is a solipsistic conclusion, but there is nothing in
our experience of consciousness that shows solipsism to be false.
The "I" is the "I" of the moment, nothing more.
Now consider the UD in arithmetic. It dovetails all possible
programs -- does all possible computations -- but most computations
have nothing to do with consciousness. If we use Boltzmann's
thermodynamics as an illustration of the situation, the computations
of the dovetailer represent a state of thermal equilibrium, a state
of maximum entropy. The characteristic of thermal equilibrium is
that every microstate is equally likely -- a state of complete
chaos. Similarly, in the dovetailer, every computation is equally
likely and there is no order whatsoever. Occasionally, in
Boltzmann's thermal equilibrium there are fluctuations to states of
lower entropy in which some order emerges, but according to the
second law of thermodynamics, these always return to equilibrium.
Similarly, in the computations of the dovetailer, there are
occasionally computations that make some sort of internal sense.
Some of these correspond to conscious moments. But, as in the
thermal case, these rapidly return to meaningless noise. Small
fluctuations to momentary order are overwhelmingly more likely than
larger fluctuations to order that persists over time -- or
computations that correspond to an extended sequence of (consistent)
conscious states. In fact, within the dovetailer there are
undoubtedly sequences of computations that correspond to the entire
history of the observable universe, from the big bang through to the
final heat death. But such calculations are of measure zero in the
overall picture.
So, if one is to take the statistics of computations that pass
through one's instantaneous conscious state in order to extract
meaningful physics, one will find that the overwhelming majority of
these computations are of short-lived conscious moments that rapidly
return to meaningless chaos, nothing more. The dovetailer would then
say that no consistent physics can ever be extracted from the
statistics over conscious moments, because these statistics are
dominated by chaotic continuations.
That does not necessarily mean that no consistent physics exists --
as I said, all of physics will be in the computations of the
dovetailer somewhere. All it means is that such physics cannot be
extracted by considering individual conscious moments as primary.
Physics has to have an independent existence, or it has no existence
at all, and solipsism is the only answer.
I guess David will explain better than me, but I think we all agree
with you: we cannot extract physics from the individual conscious
moment. But with mechanism, an individual conscious moment is, by
definition of computation, always related to one, and then an
infinity, of computational histories, and then, theoretical computer
science (and mathematical logic) shows that we get a highly non
trivial structure on the individually conscious moments, and the
physics must be extracted from that structure, not from the conscious
moments taken individually and isolated. In fact all numbers can be
seen as a computational state, if we let us chose the universal
numbers, but we have to take all universal numbers into account. I
insist, because that misunderstanding crops up very often: a
computation is NOT a sequence of states. It is a sequence of states
brought by a universal number. An then, a probable computational
histories, is just a probable universal number, taken out of an
infinity. It is always a sort of proportion, as infinitely many
universal numbers will fit, if only because many brought the same
computations. It is infinitely difficult for me to handle this without
using the counter-intuitive self-reference theory, and its modal
variants.
Bruno
Bruce
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