On 16 May 2017, at 17:34, David Nyman wrote:
On 16 May 2017 at 08:07, Bruno Marchal <marc...@ulb.ac.be> wrote:
On 15 May 2017, at 22:44, David Nyman wrote:
On 15 May 2017 at 15:56, Bruno Marchal <marc...@ulb.ac.be> wrote:
On 15 May 2017, at 12:38, David Nyman wrote:
I've been thinking a bit about physical supervenience in the
computationalist context and have come to the conclusion that I
don't really understand it. So let's consider CT + YD. YD means
accepting the replacement of all or part of my brain with a
digital prosthesis. Now, whatever theory the doctor may vouchsafe
me with respect to the function of this device, the replacement
will FAPP be, in the first (and last) instance, a physical one.
IOW after the procedure some are all of my neurological function
will be have been replaced by digital componentry (presumably some
species of logic gates) that putatively (sufficiently) faithfully
mirrors the function of the biology that has been replaced. From
any extrinsic perspective, all that will have happened (assuming
the success of the procedure) is that the net physical behaviour
of my generic brain will have been preserved to the required
extent. Notice that there is no necessary reference to computation
per se so far, however much we may wish to appeal to it in
explicating what is "actually" supposed to have occurred.
OK. For example, you might have accepted a transplant of each
individual neurons, by pig neuron. But, even here, some implicit
computationalism is used, in case you agree that the new neurons
keep the same finitely describable functions. If, not, the very
idea of that transplant tends to be irrational. You might accept
pig's neurons because you believe that pig neurons are as much
divine than human one, to give an example.
Agreed
In a minimal sense supervenience will have been satisfied, in that
my behaviour will continue to covary systematically with the net
physical action of my generic brain, but there is no necessary
reference to computation in this.
Careful, because the surgeon might need to explain you why pig's
neuron can be judged to have the right functional properties, and
if such explanation is possible in finite time, some mechanist
assumption is used.
OK
And indeed if the proposition of CTM were simply based on YD
alone, there would seem to be no further criteria to satisfy.
However, with the additional assumption of CT, it would still seem
necessary to make a further step towards explicating the relation
between the above mentioned net physical action and the relevant
spectrum of computation deemed to underlie both it and the
(perceptually) substantial terms in which it is subjectively made
manifest. The use of the word "net" in the above is noteworthy as
a little reflection will remind us that, no matter how many
"layers" of software are in principle being implemented on a given
hardware, the only relevant observable consequence is their net
physical effect, which may be rendered entirely minimal, or even
be approximated adventitiously.
It has been asserted that "physics" emerges epistemologically as a
consequence of the net perceptual integration (aka the psychology)
of an infinity of digital machines. We can say this because of the
formal equivalence of the class of such machines. This in effect
equates, in a certain relevant sense, to their having a single
such psychology, or monopsychism, albeit one that must be highly
compartmentalised by programming and the contents of memory. In
this sense, it may be possible to analogise this monopsychic
perceptual position as akin to that of a multitasking OS running
on a single "processor". There are at least two aspects to the
physics of which we speak. The most obvious aspect is the observed
behaviour of any physical system under study, which must always be
rendered in terms of the net change in some set of concrete
perceptual markers (e.g. the classic needle and dial). The second
aspect is however unobservable in principle and consists of an
abstract set of transition rules between physical states (assumed
to be finitely computable, according to CTM) between observations.
For present purposes, we may perhaps consider these rules to be
represented by the wave equation which describes the unitary
evolution of physical states.
... or some digital approximation. (to avoid some non-digital
mechanism hypothesis, à-la Penrose).
OK
A question now occurs to me. On the foregoing presuppositions, are
we to suppose that the computations representing the abstract
unitary transition "rules" of the wavefunction (i.e. the second,
abstract, part above) are *the selfsame ones* that, (under an
alternative but putatively compatible logical interpretation) are
supposed also to explicate the concrete perceptions in terms of
which the observations (i.e. the first, perceptual, part) are made?
It happens that the wave function *is* computable, so this will
follow if the Hamiltonian itself is computable. Now, it is not too
much difficult to build (mathematically) a non computable
hamiltonian. There is no evidence this exists in "nature", but
logically, computationalism can be false (and in that case, a
digital substitution will no more work a priori, or just by pure
chance, of "just" by the will of some supernatural or non-Turing
emulable entity).
If this were the case, we could indeed say that perception
supervened both on computation (under one interpretation) and
observed physical action (under a different but compatible one).
The problem will be: what do you mean by "physical action"? Human
perception can depend crucially on physical actions, but physical
actions might (and have to) emerge from arithmetic.
What I mean by physical action in this context is (approximately)
the conjunction of observed relations between concrete perceptual
objects and an abstract set of "fundamental" transition rules in
terms of which these relations can be both formulated and predicted.
I am not sure I understand in this context what you mean by
perceptual object.
Is it brought by a program, or by an infinity of programs?
Is it something computable, or is it recoverable by the first person
indeterminacy?
I mean an object *of* perception (like the apple I see). So it is
related to the p of Bp & p. Recoverable by the FPI I guess. Hence
what I term above "the relation between concrete perceptual objects"
is how correspondence with the facts is primarily established,
whether that be a reading on a dial or the abstraction of the
intuitive arithmetical notion of 2 from two objects, or from the
symbol "2" for that matter. In my view, that is. What happens next
is a separate matter.
OK.
I think that you agree that we are conscious during dreams. In that
case perception comes from random inputs to the cortex made by the
cerebral stem (in Hobson theory), and the feeling that we perceive
things is build up by the brain. few people would say that this is
a perception.
I would though.
OK? Fair enough, and that answers Brent persistent use of the
environment.
However, in this case there is no necessary relation with a
consistent covariant externality.
I might have lost the line. The question is: is there such a
consistent covariant externality?
I was a little too quick above. What I meant was that in
dreaming we are likely to be deluded about any "external
reality" we are experiencing because it will tend to be largely
an artefact of the perceptual apparatus. That doesn't of course mean
that the functioning of that apparatus, or of the organism as a
whole, is by that token disconnected from the (more correct)
externality associated with the "waking" (or more correct dreaming)
state.
OK. I would say that a dream is "more correct" when its relative
measure is closer to 1. It is more "normal" in the Gaussian sense. The
delusion comes to a stop when we realize that there is no "external
reality" except for the "arithmetical reality". That would be like the
"enlighten state", and/or perhaps death.
The point being made is that we have to justify it from arithmetic.
The "p" in Bp & p is an arithmetical proposition.
Yes of course, assuming comp. To be a little shorter in my
remarks, I don't always say this explicitly, but on the basis that
comp is being assumed in the argument you can rely on that being my
meaning.
Rather, the perception is an artefact of the perceptual apparatus
in semi-isolation from its normal input channels.
This is correct if "normal" means high probability coming from the
infinitely many input channels. Those comes from the infinitely many
universal numbers with oracles competing below our substitution level.
Agreed. Of course that's what normal or typical has to mean in
this context.
Is this compatibility in effect what is meant by Bp (i.e. the
communicable "belief in", or procedural commitment to, a finite
set of rules)
Technically, we need an infinite set of rules or axioms. But that
is a detail. We can generate UD* wilth a finite set of rules, but
each observer created in UD*, once Löbian, use infinite set of
rules in general (but that is a recursive set, so we staty in the
mechanist frame).
If you want, []p, or Bp, is all what your brain does when you see
an apple say.
Yes.
You could translate Bp by "I dream of an apple". Then an
observation is when the dream fits some reality. Bp & p becomes "I
dream of an apple" and there is an apple. The relation between both
[]p and p will be statistical, hoping the measure that we get from
S4Grz1 (in this case) will work.
Yes again. My use of the expression "procedural commitment to
a finite set of rules" is meant to imply that belief, in this
context, is to be taken to refer to much more than, say, a merely
verbal expression. Rather it implies the commitment of an entire
organism to this set of procedures.
and also p (i.e. the "true", or directly incommunicable,
correspondence between perceptual facts) implied by that belief?
Well, implied by the belief, when we restrict ourself to correct
machine.
Of course.We are not, in the first instance, dealing with
delusions.
The theory explains that this is a not constructive act. We just
never know if we are awake. We can know that we are dreaming, but
we can't know that we are awake.
Correct. But we can at least commit ourselves to the belief (i.e.
trust, or as you would have it, bet) that we are dreaming extremely
consistently and pervasively. And if that be so the distinction
between that dreaming and reality becomes otiose.
Keep in mind that "p" is a proposition of arithmetic.
Ultimately, yes.
In some sense. In other sense: we start from arithmetic, and the
(sigma_1) p behave or should behave like physical propositions, when
we take the views (Bp & p, Bp & Dt, Bp & Dt & p) into account.
physics is ultimate in that sense: it needs the statistics on the
arithmetical computations.
I think that once one accepts that physics appears as a
consequence of the machine-psychological reversal, then physics and
computation reach a kind of virtuous explanatory circularity, as
Brent often points out. One hand washes the other, as the Russians
say.
OK. I think this is what can be derived mathematically from the
"bisimulation between G and Z (or between G1* and Z1*, ...). But we
don't have this with the S4Grz1, or with X1*. One russian hand is
bigger and deeper than the other. My image is that the physical is
somehow the clothes, or the border of the universal mind (the mind of
the "virgin" Löbian machine, or perhaps already the universal machine
in general. You are trying to use intuition at the place where I
prefer to use the counter-intuitive logic of self-reference. It is OK,
as long as we don't get a contradiction with the math.
Even sigma_1 arithmetic. It asserts the existence of state, or of
an halting computation, or a number. The physical appears only for
Bp & p (with p sigma_1), or better, with Bp & ~B~p & p.
Yes.
If this were indeed the case, then the indispensable
characteristic of the necessary physics (i.e. the second,
abstract, part) that would permit it to be singled out
perceptually from the dross of the computational Babel in this way
would it be sufficiently "robust" in the relevant sense. That
robustness would consist firstly in the capacity to stabilise the
emulation of an (ultimately monopsychic) class of perceptual
machines. And secondly in that the necessary machine psychology
would supervene on common computational transition rules resulting
in a (sufficiently) consistent covariance with a concrete
externality as perceived by those selfsame machines.
That would single out a universal machine, but below our
substitution level, we need to single it out of the infinitely many
universal machine which compete to provide your next state. OK?
Yes. IIUC, this would be determined by the predominance of
(relatively) highly stable,
Yes, but not just the predominance. the logical structure imposed by
the views might play a role in weighing the computations as seen by
a subject.
Yes of course. In fact IMO the relevant predominance is that of
the narrative consistency, pervasiveness and stability imposed *by
that very logical structure*. So what would have to predominate,
for this view to be plausible, is the net monopsychic effect of a
relatively pervasive remembering (literally "putting together") of
those compelling and consistent personal narratives. This may be
conceived as the "positive" pole of a sort of subjective ambiguity,
whose "negative" antipole is an at least equally pervasive
forgetfulness and cancelling out of consequence, to the effective
relative exclusion of the myriad competing subjectively pathological
fragments. My rough analogy in this case, you may recall, was akin
to having your attention totally riveted by a very compelling and
coherent speaker standing very close to you. The thought then is
that the competing babble of random fragments emanating from a noisy
surrounding environment cannot compete, with any lasting
consequence, relative to that repertoire of powerful and
consistently connected narratives.
pervasive and consistent relations between arbitrarily many
machine points of view. It is these characteristics that in effect
would extract the necessary first-person plural measure, if this
view of the matter is ultimately to succeed. As discussed before,
it would be necessary for pathological segments of narrative (aka
white rabbits) to mutually cancel or be swamped (from the first-
person perspective) in the monopsychic measure struggle between
forgetting and remembering. I don't know if the various intuitive
analogies I've sketched recently are any help in thinking about
this. I rather liked the one about the compelling orator and the
background of babble.
The conjunction of those rules and that observed externality would
then be what we call physics and the computational physics so
particularised would in effect be distinguished by its intrinsic
capacity for self-interpretation and self-observation.
Does this make sense and if it does, what in particular about the
computationalist assumptions or inferences make such a very
specific conjunction plausible?
Well, usually we start from computationalism (basically because we
have no other theory except for fairy tales). The conjunction in Bp
& p is added (by Theaetetus) because Socrates, like Gödel for
provability, destroys the link between Bp and p. Most people would
say that when we prove things (=when we justify things rationally),
it ought to be true. But Socrates said that some people can be
wrong in their reasoning, or can have false premise, or that we
could dream, etc.), and Gödel shows that no correct machine can
prove its own Bp -> p, nor its own Bp <-> (Bp & p). We need faith
all the time, in "real life", but we can reason on simpler (but
still Löbian) than us machine, and lift, privately, the theology of
that machine on us. But that is at our risk and peril, all the
times, and it becomes explicit with the "yes doctor".
Yes, but I think there are important nuances with respect to
"true" that have frequently been missed in these conversations.
The first nuance is that there is a primary truth entailed by Bp
which is simply the perceptual "facts" it implies.
Bp -> p is true in the eye of God, but the machine cannot know that.
The machine cannot know that but the person implied by the machine
knows its primary truth beyond doubt.
OK. That is normally captured by the fact that for each p that the
machine can actually prove, Bp -> p will be provable "trivially" (in
classical and intuitionist logic, of you can prove p, you can prove
(<anything> -> p). Note that for a machine which is unsound Bp & p can
be actually false, in fact p can be false. It is madness: case where
we know something false. That does not exist in my setting, because I
limit myself to correct machine.
What can however be doubted is what exactly it refers to and what
action to take as a consequence.
Somehow p comes "first" (in a logical sense),
Yes, that's implied in a sense by what I said above.
then comes Bp, which is a bit like a window on reality.
It's also the actionable component of Bp & p.
Yes.
It is "p" as seen/believed by the subject, who can publicly share
"Bp",
Believed rather than seen, perhaps. IOW the action taken, as
remarked above.
Yes. In fact "seen" is ambiguous, but make sense in case the physical
measure exists. To see is just to believe/dream relatively to a normal
sheaf of computations.
but only hope for p, or hope in his own correctness.
Yes, it can hope that the direct perception of p (or IOW the
semantics implied by the syntax of Bp) won't lead it into mistaken
belief or action.
This, if you like, is simply the fact of the dream itself, without
any necessary entailment to a consistently covarying externality.
This, as mentioned above, can be considered an ineliminable
artefact of the perceptual apparatus. It is only after this primary
fact (i.e. the second nuance) that considerations of consistent
reference to such an externality can be considered, and it is at
this point that we can fall into error and be deluded. As you say
above, we can never be absolutely sure what our dreams refer to,
since the perceptual apparatus must be substantially the same in
all cases. Hence we can only believe and act in good faith.
Don't hesitate to tell me if I missed your question. It might help
to keep in mind that there is no physical reality: only dreams.
I think we agree.
I think too. We could differ only the intuition pump though,
perhaps. No problem, we need a lot of such pump, perhaps a different
one for each individuals.
All hands to the pumps ;)
:)
Bruno
David
Bruno
Knowing is when the dream are arithmetically true, and physical
observation is when the dream is arithmetically probable. Immediate
feeling is when the dream is probable and true.
Yup.
David
Bruno
David
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