I answer your posts.

On 19 Dec 2011, at 20:16, Quentin Anciaux wrote:

2011/12/19 meekerdb <meeke...@verizon.net>
On 12/19/2011 5:56 AM, Bruno Marchal wrote:
In this case, the distinction is more than merely linguistic. Often
when you say PA is conscious, I translate your comment as above, and
continue on.

When I say that PA is conscious, I mean it literally.
When I say that RA is conscious, I mean "the universal machine RA" is conscious literally. But RA can also play the role of a universal dovetailer, which is not a person, and thus not conscious. RA can play both, somehow. Like any universal machine, even a Löbian one, can implement a universal dovetailing (if patient enough!).

But this can't be done here.

I agree that the UD is not a person, and as such its consciousness is even non-sensical. But if you agree that the UD instantiates consciousness, then the MGA applies to it. I can say yes to a doctor because it takes a much lower level than the correct one, putting much to much in the artificial brain. And you were saying MGA does not work in case of a physical supervenience based on a multiverse. That is why I put the level so down so that I emulate that multiverse, making MGA working on that structure. An infinitely low level can only force me to implement (as my brain) a multiverse, or even the universal dovetailing itself. This will subsumes all multi- multi-multi-multi .... (^alpha) universes (alpha constructive ordinal).

This is related to my point that consciousness is relative to some context. ISTM that pushing the substitution level down so low that you are emulating the physics of the environment as well as the brain vitiates the argument. If I emulate a universe or multiverse in order to instantiate consciousness then I have not shown consciousness to be independent of physics. I've only shown that consciousness supervenes on the physics of the emulated multiverse.


Also I can't see how the view that the physics emerge from invariance of infinities of interfering computations allows physics to be entirely simulated in one computation (ultra low substitution level).

Such physics can no more be simulated, except by a big dovetailing. In the worst case, by the universal dovetailing itself. It does not strictly speaking "simulate" the physics, but for someone deciding to put the level that low, it means asking the UD for a brain, + the hard (*very* hard) task to interface the correct one in that UD with your environment.

ISTM that if the level is that low... then comp is false, because physics utlimately must be not computable...

I sort of agree. But not-comp is consistent with comp: with very low level we can no more say yes to a doctor, and have to count to a dovetailer. Not comp might be approached by the limit of comp for the level getting infinitely low. It think this makes the multiverses themselves interfering, getting alpha-multiverses with alpha constructive ordinal. If alpha is bigger than Church-Kleene's omega-1 (the least non constructive ordinal), then comp is false, and physics is no more computable.

digital physics is not compatible with computationalism, but, an ultra low level is digital physics and that's contradictory.

Why would an ultra-low level necessarily make physics digital?
An ultra low level exploits the multiverse below a higher level, in some sense. It is like saying yes to the doctor when he proposes to you a quantum brain. That can only makes the physical reality even more complex, and less computable, from the first person perspective (as physics normally is).

And also, ISTM that a substitution level embedding all the multiverse is *infinite* hence not turing emulable.

Many infinite are turing emulable, by dovetailing. Digital physics assume the physical world to be the result of execution of one program (if not the output in some other version). This might win the measure battle, in UD*, for the appearance of physics, only if *you* are that "physical" (and digital) universe. I doubt this makes sense.

From your other post:

what about the fact that a generalized brain which would need all the universe to be simulated seems contradictory to what you say about digital physics being false if comp is true ? That move (ultra low substitution level) seems an invalid move to keep comp.

If it means all the multiverse, the physics is still not necessarily digital, but it relies on the comp indeterminacies, like if we have a quantum brain.

Lowering the level can only be a way of exploiting the comp indeterminacies. You can indeed save digital physics, by making your own consciousness supervenes exactly on the UD emulation of exactly that program (and its equivalent for any level). But then:

- You will have a problem in justifying the consciousness of others.

- And, accepting MGA (and "323"), you will have a problem due to the statistical interference of other digital programs still going through your actual computational state in the UD. That unique digital universe has to have the way to fight those interferences.

Do you see what I am saying. I think I could be clearer. I see that "making the level lower" has not the same meaning if we still assume that one program (other than a UD) can generates the physical "appearances".
That notion of level is tricky.

Don't hesitate to tell me that you are not happy with this answer.



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