On 14 Aug 2014, at 10:34, Russell Standish wrote:

On Thu, Aug 14, 2014 at 09:59:31AM +0200, Bruno Marchal wrote:


A human being or any physical system reacts to the world in one
way or another.  What was asked was for was counterfactual
correctness, i.e. the the MG reacts the same as would the
conscious being emulated - which might be no change at all.

I agree with you. The counterfactualness needs "If we change the
input then the output will change in the relevant way".  But I am
not sure that we need the actual (physical) counterfactual behavior.
I might differ from Russell here.


Counterfactual correctness is needed as part of the computational
supervenience thesis in order to forbid supervenience on recordings.

Counterfactual Correctness (hereafter CC) is an attribute of a machine (or a program) which compute some function. In a first approximation, the machine is CC is it computes the right function whatever the input is.

We can extend the sense of CC on a computation, and say that a computation is CC, if it is the computation (done by some universal machine) of some CC program. We suppose by defalut that the universal machine executing that CC machine/program is itself CC.

So I think that CC is already needed for having a computation, although in practice, the CC character can be restricted on its domain (the machine computes correctly the function, unless some input is too big, for example).

Let me try to be slightly more technical. People can ask question if they don't remind the meaning of a term here.

Let phi_i be an enumeration of all partial computable functions (= programmable on a computer).

I will call a computation "raw" if it is described by a sequence phi_i(j)^n. So it is the steps of the computation of the UD itself, when computing the n first steps of the computation of the function phi_i (= executing the first n step of program i) on the input j. OK?

Here, it is the program or machine i which is CC, and this makes sense only relatively to some semantics. A program computing wrongly the factorial function, might be said to compute correctly some variant of the factorial function!)

Now the computationalist supervenience thesis will associate consciousness to an abstract entity, called the first person (and approximated by the believer/prover + truth). Here the truth (as we assume comp) is (notably) that the relevant computational state belongs to an infinity of raw computations made by the UD. By definition they are all CC (in the extended sense). When they diverge on different inputs (like Washington or Moscow) they both do the relevant corresponding behavior.

So, counterfactualness is "in" the program (even before it run), and is kept in the raw computations corresponding to the relevant program in the UD.

To sum up: the computationalist supervenience thesis associate a conscious state (including its feeling being at this time at this place) to an infinity of computations, which are CC by definition of computations.

Now, a record of a computation, is obviously not CC. I would say that it does not compute at all. It is a description of the sequence of steps of a computation, but there is no universal machine going through those steps in virtue of being itself a universal computer. The movie projector, in particular does not compute (or just in a weak sense unrelated to the computation it projects the movie of).

I disagree with your idea that to have counterfactual correctness we need the actualisation of the diverging computations. We do have them in UD*, so that is not a problem. But we don't need them.

If I give a classical well defined input to a classical (non quantum) program, it will computes the same output, from the same input in all the multiverses, except for the non normal "white rabbit" worlds. The quantum counterfactualness (which exists and can be related to the multiverse structure) does not seem relevant here, except that UDA imposes such an actualization of different computations below our level of substitution (and this will be confirmed by the machine's talk about the []p & <>p, which gives a quantum logic (and quantum logic are sort of logic of counterfactual or conditionals, as shown by Hardegree).

The problem with physical supervenience, is that we can build a record of a computation (thus non conscious), but becoming CC when inactive physical stuff is in its neighborhood, making weird the role of the physical with respect to consciousness. This suggests that the (often considered immaterial) consciousness is related to the immaterial set of raw computations going through that states, or up to that states (ate least something like that), and not to any of its particular emulation by the UD, or another program (non raw computation, itself done by a raw computation).




Physical supervenience is something observed.

I don't understand what you mean by that. I think you might mean that we do attribute consciousness to "normal brains", and we can do that indeed with comp. But the real person is in Platonia and is distributed to infinitely may emulations in Platonia or UD*. In this case it is a little, and computer generable platonia, as it is the effective enumeration of the true sigma_1 sentences. It is equivalent with UD*).



Again, in order to
prevent supervenience on physical recordings, actual physical
counterfactuality is required - which is basically the quantum nature
of physical reality.

This is close to something I find deep (and plausible) but you are too quick, at least for me. And you do use, like deutsch the idea that the counterfactuals need to be realized to make sense, but I disagree with this, even if they $are* all realized in the sigma_1 arithmetic. This reminds me that I do think we can extract the quantum nature of reality from MGA+Maudlin, in a sense deeper than in step 7 (where physics has already a quantum aspect due to the infinitely many computations which "interfere" statistically below our substitution level, especially compared to the Feynman sum of history formulation of QM). But for this I need Hardegree result showing that QL, with the Sazaki hook implication, which is nice because the orthomodularity becomes equivalent with the modus ponens, provides a logic of conditional/ counterfactuals, and apparently the logics []p & p, []p & <>p, []p & p & <>p do that too, when p is restricted to the sigma_1 sentences.

But we need, if you are correct, only *that* sort of actualization of the counterfactuals, and that can't be used to attribute a "primitively material" character to it.

OK?

We might need to work on this. The problem is that counterfactual are counterintuitive and that is why I tend to trust more the logics G1(*), S4Grz1, Z1(*), X1(*) than my intuition on this.

Cheers

Bruno


http://iridia.ulb.ac.be/~marchal/



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