On 9/05/2017 1:57 am, David Nyman wrote:
On 8 May 2017 8:21 a.m., "Bruce Kellett" <[email protected]
<mailto:[email protected]>> 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.
Bruce
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