On 5/8/2017 10:16 PM, 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.
I agree with that except I think you are not recognizing a drastic
difference of scale. A human conscious thought is something with
duration, something on the order of tens of milliseconds. The
substitution that you say "yes, doctor" to, must operate at a much
higher frequency. So I conceive of the UD producing threads of
computation consisting of many successive states within one "thought"
and there will be threads in other programs being executed by the UD
which are sufficiently similar over this sequence of states as to
constitute the "same thought" because thoughts are classical level
emergent things. In Barbours metaphor this a kind of stream of fog. If
you take this view of thoughts having duration then they can overlap and
form a kind of continuum. Bertrand Russell gives this analysis of time
as a perception in one of his more technical papers. But a consequence
of this is that what picks out a "thought" from just noise is this
persistent coherence over the duration of many (countably infinitely
many) thread of UD computations. This persistence is what constitutes
physics in that consciousness because it must account for all
interactions that are perceived as external and it must make them more
coherent than just noise. So a happy solution to the measurement
problem would be to show, purely as a matter of arithmetic, that such
coherent threads of significant length have high measure.
Brent
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.
Bruce
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