On 04 Apr 2015, at 01:26, Bruce Kellett wrote:
meekerdb wrote:
On 4/2/2015 8:55 PM, Bruce Kellett wrote:
The only reason that the dovetailer might have to worry about time
limitations is if it is actually a physical computer. Physical
computers have to contend with such things as physical laws, the
finite speed of light, the properties of materials, the generation
of heat (entropy) and the need to remove that heat to a safe
distance before everything melts down. If your computer is not a
physical device, then it has none of these limitations, and there
is no such concept available as the 'speed' of the computation,
the 'time for each step', or anything of this sort. From our
external concrete perspective, the whole thing is instantaneous,
or it enters statis at some point and gets nowhere. For a non-
physical computer these things are equivalent.
So without a physical computer you have no dynamics. A mere
ordering of states is still a static thing, and the dovetailer
does nothing useful that could not more easily be done by
referring to a normal number.
Why would it not have the same dynamics as in any Platonia version
of physics, e.g. a block universe simulated in a digital computer?
The states don't even have to be computed in their inherent time
order.
Bruno doesn't argue for this -- as far as I can see he moves from a
physical computer straight into Platonia,
? No, I often use the block universe to illustrate the similarity
here. and I don't move straight into "Platonia", I use the MGA, and
eventually the math.
without any attempt at a justification for the move.
You have not answer the question: do you agree that at step 7, and
thus in presence of primitive physical universe running a universal
dovetailer, physics is reduce to a mathematical problem.
Unfortunately for his case, if you start with a physical computer,
you have to start with a set of physical laws and that will run this
machine composed of physical matter in an orderly manner. It cannot
bootstrap itself -- run the machine and this itself generates the
laws that enable the machine to run? Argue the self-referential
bootstrap, don't just ignore the problem.
To avoid such problem, I divided the reasoning in smaller step. I
can't comment this without knowing if youe have seen the reversal in
step seven. It looks you do. So what you say amount to say that you
believe there is something wrong in the MGA.
OK, so what is wrong?
But a more significant point, it seems to me, is that time in the
block universe works by taking some subsystem and using it as a clock.
But that can be done in the simulation of the Milky Way, or of any
computable solution of some physical laws. And also, in
"platonia" (sigma_1 arithmetical truth), you have a universal clock:
the steps of the UD itself.
But the clock function is instantiated by showing correlations
between the regular dynamics of the clock and the dynamics of the
rest of the universe. In other words, the universe has to run
according to regular dynamical laws that apply equally to the clock
subsystem and to the rest. Without these regular correlations you
have no clock, and no time.
Digitalness entails the existence of a universal time, given by the
ordering of the steps of the UD, which can be defined in arithmetic.
Of course, that universal time has only quite indirect relations with
possible physical time, which emerge from inside, in the first person
view of the entities emulated by the UD. Your argument is not valid.
Barbour's solution is rather different, and more ingenious, because
he doesn't actually recreate physical time or dynamics. He simply
connects otherwise unrelated slices by his 'time capsules'. One can
argue for ever whether this actually works, but it is an ingenious
possibility.
The computer's memories of the entities emulated by the UD
(equivalently sigma_1 arithmetic) plays the role of time capsule, and
can be defined formally in arithmetic.
The problem I see is that Bruno has not made any attempt to argue
for any sensible notion of time when he moves into Platonia.
I submit a problem for the computationalist.
Now you are unfair, because the math part shows the solution (and show
it empirically testable). Both a physical time and a subjective time
emergence is explained with all details.
The fact that you say that I made no attempt is proof that you have
not yet begin to study the reasoning, the problem and the illustration
of testable solution.
He can refer to relations among numbers in arithmetic as
'computations', but that is just a play with words -- there is still
no dynamics involved.
There is, and as Brent argue correctly, it is similar to any block
universe theory, except that I show the "block-reality" is bigger,
immaterial, and might contain white rabbits, and then I show why those
white rabbits seems to disappear by a process similar to Feynman
quantum phase randomization. This lead to open problem in mathematical
logic (one has been solved by a student of mine).
And Bruno really does need dynamics in order to make a computational
model of consciousness different from a static recording.
I need the digital dynamics -, and that one is provided by the step
notion of computation. That involves only the static notions of
successor, addition and multiplication.
The MGA is an argument from incredulity -- it is not a valid argument.
You might elaborate. See my answer to Russell.
This is why I have said several times in previous posts that you
rely on an underlying notion of physical time, and an underlying
physical computer, in order to make your computation dynamic and
not static. What you say above does not let you escape from this
conclusion, it merely reinforces it. The problem of time is your
undoing.
I think the UD necessarily takes unlimited time. Given any
particular state the UD will visit that state infinitely many times
and compute infinitely many different successive states. It
doesn't halt, so all the different successor states are never
completed. These states may be indexed by some internal time, per
Barbour.
I agree that the UD, implemented physically, will take an infinite
time and will compute an infinite variety of variations on any
particular state -- though why we should happen to find ourselves in
a state with other people and a physical world remains unexplained.
That is my point. And the answer will be given by the discourse on
what is observable made by the universal (Löbian) machine.
The Boltzmann brain problem is probably worse for Bruno than the
white rabbit problem.
Too vague. A priori it is the contrary, as the UD expliciltly build
among many other things all Boltzman brain of any size, and run them
entirely, without using probabilistic considerations.
Nevertheless, without actually providing a solution to the problem
of time in his model -- which involves justifying the step from a
physical computer running the UD, to Platonia
That step is the main content of the work. And yes it leads to
problem, and I show how to solve them, and I give the entire solution
at the propositional level, adding only to comp the idea-definition
that knowledge obeys the axiomatic of the logic S4 (all analytical
philosophers agree with this).
which is static -- Bruno has not, it seems to me, demonstrated that
consciousness is a computation in unphysical Platonia.
Even you read the works, you should understand that consciousness is
not a computation in unphysical platonia, nor is matter.
You give me the feeling that you criticize a vague simplification of
the work and not the work itself. The work is deductive and does not
propose any new theory. It would ease the progress of the conversation
if you could say where you have a precise problem in the reasoning.
Of course we have Platonia right at the start, and you have no problem
with it, given that platonia is only the idea that 2+2=4 independently
of me and you. So, at step zero, we already know that the computations
exist in "platonia" (that follows from 2+2=4, or the axioms given).
But at that stage, we can still hope that the physical will do the
difference, and this is shown epistemologically contradictory with the
MGA, unless you believe that a recording can be conscious, or that
inactive objects at time t can have an active role at time t, etc.
Let us be sure you are OK up to step 7, and then we can discuss more
easily the step 8.
Bruno
Bruce
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