Bruno Marchal wrote:
On 06 Apr 2015, at 13:25, Bruce Kellett wrote:
You want a dynamic like in physics, a function from time to space, but
in computer science, and to understand the problem here, the dynamics
are given by function from N to "mind states".
You need to give magical ability to a turing machine so that she can
distinguish (by its consciousness, in a first person way) the difference
between a physical emulation, and an arithmetical emulation. The
physical will give rise to the right measure, but not by magic, only
because the physical is run by the sum on all computations below its
substitution level.
But all this is not needed to get the reversal in step seven. So I guess
again that you are OK with step seven and see that if a primary physical
universe exists and run the UD, then physics is reduced to arithmetic
(seen from inside). Do you see that.
I understand what you are claiming, but I do not agree with it. The
primary physical universe certainly exists, and it is not running your
UD! I think we might notice if it were.
I think that Russell is right when he suggested that even by step seven
your dovetailer has to be running in Platonia, not in a physical
embodiment. This has to do with the fact that the dovetailer can never
complete. It is running all possible programs and most of these will
never complete. So you never complete and get back to running all the
steps of early programs in the sequence. So you do not compute all
possible instantiations of a conscious moment by any finite time in a
physical universe. Or even in Platonia because the idea of a completed
infinity of computations makes no sense.
So no conscious moment, even in with a dovetailer in Platonia, can ever
be completely counterfactually correct, because there will always be
related sequences of states that never get to be computed -- no
completed infinities even in arithmetic.
Physics is not reduced to arithmetic seen from the inside because
arithmetic is never completed by the dovetailer or anything else and
there are no non-magical ways in which similar states that might give
rise to ordered physical laws can ever be be related.
You only ever get out of a model like this what you put in. You have put
in arithmetic, so that is what you get out. You will never get physics
this way.
Bruce
With occam, a believer in comp can
already stop here, and work on the measure problem.
But a phsysicalist can still conclude that there is a primary unique
universe, and that it can't run the UD, nor any significant part.
The step 8 address this situation and shows precisely why invoking a
primary physical universe makes it magical, with neuron needing
prescience, and movie getting experiences, and indeed nothing getting
all experiences.
It is good news, as it suggest we might understand the origin of the
physical laws, from non physical things, the gluing properties of
universal numbers' dreams.
Bruno
Bruce
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