On 8/05/2017 3:59 pm, David Nyman wrote:
On 8 May 2017 4:53 a.m., "Bruce Kellett" <[email protected]
<mailto:[email protected]>> wrote:
On 8/05/2017 3:14 am, David Nyman wrote:
On 6 May 2017 11:04 p.m., "Brent Meeker" <[email protected]
<mailto:[email protected]>> wrote:
On 5/6/2017 2:45 PM, David Nyman wrote:
On 6 May 2017 10:16 p.m., "Brent Meeker"
<[email protected] <mailto:[email protected]>> wrote:
But that's what I mean when I say Bruno's theory has no
predictive success. QM (and Everett) would correctly
predict that alcohol molecules in the blood will
interfere with neuronal function and THEN invoking the
physicalist theory of mind, i.e. that mind supervenes on
material events, it predicts that your ability to do
arithmetic will be impaired by drinking tequila. It
will NOT predict the contrary with more than
infinitesimal probability. So it's misdirection to say
that it's just a measure problem. Without having the
right measure a probabilistic theory is just
fantasy...or magic as Bruno would say.
I have no idea why you say that. I thought it was clear that
if computationalism doesn't (ultimately) predict that its
predominating computational mechanism (i.e. the one
effectively self-selected by complex subjects, in this case,
like ourselves) is the physics those selfsame subjects observe,
That would certainly be an accomplishment - which in another
post Bruno says is trivially accomplished even in RA (I don't
see it). But to succeed in prediction it is not enough to
show that some world exists in which mind and physics are
consistent (that the physics that mind infers is also the
real physics that predicts effects on the mind). You need
also to show this has large measure relative to contrary
worlds. One can make a logic chopping argument that it must
be that way for otherwise minds would not be making sense of
the physics they perceived - but that makes the whole
computational argument otiose.
I've been thinking a bit more about this and I'd like to set out
some further tentative remarks about the above. Your professional
expertise in these matters is orders of magnitude greater than
mine and consequently any comments you might make would be very
helpful. By the way, it would also be helpful if you would read
beyond the next paragraph before commenting because I hope I will
come by myself to the fly in the ointment.
Firstly, and "assuming computationalism" on the basis of CT + YD,
we are led to the view that UD* must include all possible
"physical" computational continuations (actually infinitely
reiterated). This of course is also to assume that all such
continuations are finitely computable (i.e. halting). Now, again
on the same assumptions, it might seem reasonable that our
observing such a physics in concrete substantial form is evidence
of its emergence (i.e. epistemologically) as the predominant
computational mechanism underlying those very perceptions. Hence
it might seem equally reasonable to conclude that this is the
reason that these latter correspondingly appear to supervene on
concrete physical manifestations in their effective environment.
Now wait a minute. We cannot escape the question of measure. Why
would it be reasonable to assume that a physics of this sort
should predominate in the manner outlined above? Well, firstly,
it would seem that the generator of the set of possible physical
computations is infinitely reiterative and hence very robust
(both in the sense of computational inclusiveness a la step 7,
and that of internal self-consistency). But who is to say that
the generators of "magical" or simply inconsistent continuations
aren't equally or even more prevalent? After all we're dealing
with a Library of Babel here and the Vast majority of any such
library is bound to be gibberish. Well, I'm wondering about an
analogy with Feynman's path integral idea (comments particularly
appreciated here). Might a kind of least action principle be
applicable here, such that internally consistent computations
self-reinforce, whereas inconsistent ones in effect self-cancel?
Also, absence of evidence isn't evidence of absence. I'm thinking
here about the evaluation of what we typically remember having
experienced. I can't help invoking Hoyle here again (sorry).
Subjectively speaking, there's a kind of struggle always in
process between remembering and forgetting. So on the basis
suggested above, and from the abstract point of view of Hoyle's
singular agent (or equally Bruno's virgin machine), inconsistent
paths might plausibly tend to result, in effect, in a net
(unintelligible) forgetting and contrariwise, self-consistent
paths might equally plausibly result in a net (intelligible)
remembering. I'm speaking of consistent and hence intelligible
"personal histories" here. But perhaps you would substitute
"implausibly" above. Anyway, your comments as ever particularly
appreciated.
I think the problem here is the use of the word "consistent". You
refer to "internally consistent computations" and "consistent and
hence intelligible 'personal histories'." But what is the measure
of such consistency? You cannot use the idea of 'consistent
according to some physical laws', because it is those laws that
you are supposedly deriving -- they cannot form part of the
derivation. I don't think any notion of logical consistency can
fill the bill here. It is logically consistent that my present
conscious moment, with its rich record of memories of a physical
world, stretching back to childhood, is all an illusion of the
momentary point in a computational history: the continuation of
this computation back into the past, and forward into the future,
could be just white noise! That is not logically inconsistent, or
comutationally inconsistent. It is inconsistent only with the
physical laws of conservation and persistence. But at this point,
you do not have such laws!
In fact, just as Boltzmann realized in the Boltzmann brain
problem, states of complete randomness both before and after our
current conscious moment are overwhelmingly more likley than that
our present moment is immersed in a physics that involves
exceptionless conservation laws, so that the past and future can
both be evolved from our present state by the application of
persistent and pervasive physical laws.
Unless you can give some meaning to the concept of "consistent"
that does not just beg the question, then I think Boltzmann's
problem will destroy your search for some 'measure' that makes our
experience of physical laws (any physical laws, not just those we
actually observe) overwhelmingly likely.
Thanks for this. However I'm not sure you've fully addressed my "path
integral" point, for what it's worth. Feynman's idea, if I've got the
gist of it, was that an electron could be considered as taking every
possible path from A to B, but that the direct or short paths could be
considered as mutually reinforcing and the indirect or longer paths as
mutually cancelling.
Feynman's ideas relies on a physical theory within which one can
calculate the phase change along each possible path. The upshot is that
paths far away from the path of least action have phases that cancel in
the quantum superposition sense. Note that the crucial input into this
picture is that there is an underlying physical theory, in terms of
which one can calculate the phase changes along each path. Also, it is
important to remember that Feynman's path integral is only one means of
calculating probability amplitudes in QM -- there are many other means
of calculating these, and all give the same results.
Hence the derivation of the principle of least action. So the analogy,
more or less, that I have in mind is that Boltzmann-type random
subjective states would, computationally speaking, mutually reinforce
identical states supervening on the generator of "consistent" physical
continuations (bear with me for a moment on the applicable sense of
"consistent" here). IOW "If I am a machine I cannot know which machine
I am". So as long as the generator of those consistent states is
encapsulated by UD* - which is equivalent to saying as long as the
computable evolution of physical states is so encapsulated (which it
is by assumption) - then we can plausibly suppose that the net
subjective consequences would be indistinguishable.
I agree that conscious states, whether Boltzmann brains or parts of a
longer calculation that does not start and end in white noise, are,
insofar as thise states are conscious, they are indistinguishable. But
the Boltzmann brain-type states cannot reinforce the path that leads to
coherent physics, because the continuations are disjoint.
As to your most reasonable request for a non question begging notion
of consistent in this context, my tentative answer rests on my remarks
about the "struggle between remembering and forgetting". Here's where
I use Hoyle's pigeon hole analogy, which is pretty much equivalent to
Barbour's time capsule one (as he acknowledges in TEOT)
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.
or for that matter the "point of view" of a machine computing a
partitioned multitasking OS. All of these analogies, or heuristics as
I prefer to think of them, enable one to think about the entirety of
subjective experience as though from the first person perspective of a
single agent - one of course with a massive case of multiple
personality accompanied by extreme dissociation between each of the
personalities.
The only connectivity between discrete states of the overall system is
that which is logically internal to each state.
But what gives that internal logic? Boltzmann brains are internally
logical in their own terms. If you take your present memories of a past
world as part of your conscious state, and require that future
continuations be consistent with those memories (along Barbour's time
capsule lines), then you are building most of physics into your notion
of consciousness. This may very well be what is required, but I do not
see that as an explanation of consciouness in terms of arithmetical
realism or computationalism, or as an explanation of physics in terms of
the UD.
Of course on reflection we realise that most plausibly the brain must
somehow contrive just such relations between states, as becomes most
obvious when this mechanism goes wrong in dementia and other
neurocognitive insults.
But you know this only from your experience of the physical world --
that is not currently in evidence.
So "consistency" here would reflect the fact that these very
conversations, for example, form part of a coherent internally linked
history of remembering, whereas inummerable incoherent states simply
*cannot be recalled* from the perspective of such consistent
histories. Hence what is consistent is equivalent to what is, in the
net, remembered (recalling in passing the etymology of this word) as
distinct from what is, in the net, disremembered.
But how do you know that your memories are veridicial of anything at all
-- they could just be fluctuated into existence as part of your
momentary conscious state.
I'm reasonably confident that this justification isn't merely
circular, or that if it is, it may well be one of Brent's virtuously
circular explanations. What do you think?
I don't think the circle is virtuous. You are required to define
"consistent" in a way that does not refer to physical laws. The only
other consistency that I know is logical consistency, and mere logical
consistency does not avoid the Boltzmann brain problem.
Bruce
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