On 9/27/2011 1:27 AM, Bruno Marchal wrote:
On 26 Sep 2011, at 21:44, meekerdb wrote:
On 9/26/2011 9:08 AM, Bruno Marchal wrote:
Suppose that you are currently in state S (which exist by the comp assumption).
But what does "you" refer to?
Your first person view. Or the owner of your first person view, restricted to that view,
without salvia amnesia, if you want.
The comp assumption seems ambiguous. Is it the assumption that "you" are instantiated
by a specific computation?
No. Something like that can be part of the consequence, but this is clearly not assumed.
In fact the UD shows that "you" is instantiated by an infinity of computations.
Or is it the assumption that your brain could be replaced, without you noticing, by a
physically different computer, so long as it computed the same function (at some level).
These seem slightly different to me and are only identical if QM is false and the world
is strictly classical and deterministic. At a practical level the brain is certainly
mostly classical and so I might say 'yes' to the doctor even though my artificial brain
will have slightly different behavoir because it has different counterfactual quantum
behavior. But this difference seems to present a problem when trying to identify "you"
within the inifinite bundle of computations instantiating a particular state in the UD
Why? If my "original brain" is described by QM (without collapse) it might be said to
self-multiply naturally. But that self-multiplication will be contagious on the UD in
that universe, so this will not change the relative proportion.
That's the step that seems ambiguous. What you write above applies to a physically
realized (i.e. quantum) UD, but not to the UD in Platonia. The physically realized UD
will have non-zero probabilities of doing something random instead of implementing the
On the contrary, the UD itself forces a multiplication to be lived from inside.
As to identify yourself in the UD*, this is just impossible in any third person ways.
But the indeterminacy is on the first person experiences, not on their description in
the UD. So the statistics are lived from inside. A computation is winning, if indeed you
feel to be alive through its UD instantiation.
Ambiguities remain, but they are part of the measure problem.
Of course if you replace the whole universe with an emulation, instead of just my
brain, then my emulated brain in the emulated universe can have the same behavior as my
natural brain in this universe.
Yes, and that is why the reasoning will work in the limiting case where your
"generalized brain" is the entire universe described at some level. The UD will generate
all the digital approximation of that universe, and at some level of approximation, you
will not see the difference, because we are assuming comp.
The UD generates an infinity of computations going through that state. All what I say
is that your future is determined by all those computations, and your self-referential
abilities. If from this you can prove that your future is more random than the one
observed, then you are beginning to refute rigorously comp. But the math part shows
that this is not easy to do. In fact the random inputs confer stability for the
programs which exploits that randomness, and again, this is the case for some
formulation (à-la Feynman) of QM.
How is this?
Consider the iterated self-duplication experience, like with the random movie, where you
expect to see (correctly) a random movie. The movie will seem random because the
limiting case is described by a Gaussian (accepting the p = 1/2 for a single
duplication). Other considerations make such a randomness occurring below you
substitution level, so it might be that the only way to stabilize the computations above
the substitution level comes from some phase randomization, similar to Feynman
explanation of why QM minimize the path action.
So you're talking about keeping the computation classical, even though realized by a
physical device which is microscopically quantum? I don't recognize the reference to "the
We need a notion of negative (amplitude) of probability,
Negative probability or negative, imaginary probability amplitude?
extracted from comp, for such a procedure to work, but this is already provided by the
logic of self-reference when we add the non-cul-de-sac assumption (Dt) to the
provability modality (Bp), with p sigma_1. This can be made enough precise to make sense
of how the quantum can be explained by the digital viewed from the digital creature
themselves. No doubt that a lot of work remain to be done, but that is exactly what I
wanted to show.
You lost me.
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