On 12 Dec 2011, at 04:39, Joseph Knight wrote:

On Sat, Dec 10, 2011 at 6:39 AM, Bruno Marchal <marc...@ulb.ac.be> wrote:

On 09 Dec 2011, at 19:47, Joseph Knight wrote:

On Fri, Dec 9, 2011 at 3:55 AM, Bruno Marchal <marc...@ulb.ac.be> wrote:

The heap argument was already done when I was working on the thesis, and I answered it by the stroboscopic argument, which he did understand without problem at that time. Such an argument is also answered by Chalmers fading qualia paper, and would introduce zombie in the mechanist picture. We can go through all of this if you are interested, but it would be simpler to study the MGA argument first, for example here:


There are many other errors in Delahaye's PDF, like saying that there is no uniform measure on N (but there are just non sigma- additive measures), and also that remark is without purpose because the measure bears on infinite histories, like the iterated self- duplication experience, which is part of the UD's work, already illustrates.

All along its critics, he confuses truth and validity, practical and in principle, deduction and speculation, science and continental philosophy. He also adds assumptions, and talk like if I was defending the truth of comp, which I never did (that mistake is not unfrequent, and is made by people who does not take the time to read the argument, usually).

I proposed him, in 2004, to make a public talk at Lille, so that he can make his objection publicly, but he did not answer. I have to insist to get those PDF. I did not expect him to make them public before I answered them, though, and the tone used does not invite me to answer them with serenity. He has not convinced me, nor anyone else, that he takes himself his argument seriously.

The only remark which can perhaps be taken seriously about MGA is the same as the one by Jacques Mallah on this list: the idea that a physically inactive material piece of machine could have a physical activity relevant for a particular computation, that is the idea that comp does not entail what I call "the 323 principle". But as Stathis Papaioannou said, this does introduce a magic (non Turing emulable) role for matter in the computation, and that's against the comp hypothesis. No one seems to take the idea that comp does not entail 323 seriously in this list, but I am willing to clarify this.

Could you elaborate on the 323 principle?

With pleasure. Asap.

It sounds like a qualm that I also have had, to an extent, with the MGA and also with Tim Maudlin's argument against supervenience -- the notion of "inertness" or "physical inactivity" seems to be fairly vague.

I will explain why you can deduce something precise despite the vagueness of that notion. In fact that vagueness is more a problem fro a materialist than an immaterialist in fine.

How so?

With comp, if you want introduce a physical supervenience thesis, the physical activity can only mean "physical activity relevant with the computation". So we can say that a physical piece of a computer is inert relatively to a set S of computations in case the computations in S are exactly executed with and without the physical piece. Digitalness makes the notion of exactness here sense full. If someone says that such a piece of matter has still some physical activity involved in the computation, it can only mean that we have not chosen the right level of implementation of those computations. If a materialist can convince someone that such a piece, which has no role for the computation in S, has some role, for S bearing a first person perspective, then we can no more say "yes" to a doctor, in virtue of building a device which will emulate correctly the computations in S (assuming some of them corresponds to a conscious experience).

Indeed, it is not yet entirely clear for me if comp implies 323 *logically*, due to the ambiguity of the "qua computatio". In the worst case, I can put 323 in the defining hypothesis of comp, but most of my student, and the reaction on this in the everything list suggests it is not necessary. It just shows how far some people are taken to avoid the conclusion by making matter and mind quite magical.

I think it is better to study the UDA1-7, before MGA, and if you want I can answer publicly the remarks by Delahaye, both on UDA and MGA.

I feel quite confident with both the UDA and the MGA (It took me a little while).


I read sane04, and quite a few old Everything discussions, including the link you gave for the MGA as well as the other posts for MGA 2 and 3.

I might send him a mail so that he can participate. Note that the two PDF does not address the mathematical and main part of the thesis (AUDA).

So ask any question, and if Delahaye's texts suggest some one to you, that is all good for our discussion here.

My main question here would be: when Delahaye says you can't (necessarily) have probabilities for indeterministic events, is that true?

Simplifying things a little bit I do agree with that statement. There are many ways to handle indeterminacies and uncertainty. Probability measure are just a particular case. But UDA does not rely at all on probability. All what matters to understand that physics become a branch of arithmetic/computer science is that whatever means you can use to quantify the first person indeterminacy, those quantification will not change when you introduce the delays of reconstitution, the shift real/virtual, etc. Formally, the math excludes already probability in favor of credibility measure. But for the simplicity of the explanation, I use often probability for some precise protocol. The p = 1/2 for simple duplication is reasonable from the numerical identity of reconstituted observers. We have a symmetry which cannot be hoped for any coins!

Credibility measure? What's that?

Let T be a finite set, and 2^T its power set. A belief function b is a function from 2^T to [0, 1] quite comparable to a probability function. We have for example that b({ }) = 0, and b(T) = 1. The main difference is we don't ask for the Poincare identity, we ask only for an inequality:

if Ai are subsets of T, we ask that

b(A1 U A2 U ... U An) bigger or equal than Sum_i b(Ai) - Sum_i < j b(Ai inter Aj) + ...

For probability we ask an equality. I see that in english they use "belief", but in french we use "croyance" (credibility).

This leads to a variant of probability calculus which can handle better the notion of ignorance than the bayesian approach.
You might Google on "Dempster Shafer theory of evidence".

Modal logics can be used to formalize the "certainty" case. Alechina, in Amsterdam, has shown that the normal modal logic K + the formula D (Bp -> Dp) formalizes this "certainty" completely, and we get something similar in the relevant variants of the self-reference logics. (B = [ ], D = < >), except that we loose the modal necessitation rule, like for the quantum logics.

This is just one example of a calculus of uncertainty (apart from probability). There are theories of possibility, of plausibility, etc. Dempster-Shafer theory of evidence got some success in criminal inquests, medical diagnostic, finding location of secret submarines, debugging and inductive inference. It is particularly useful when we don't want to ascribe a uniform probability in case of ignorance, which is the case when we ignore the content of the set T, that is when we have only partial knowledge on the elementary results of the random experiences. It works also better on vague or fuzzy sets. I am not an expert in that field, but my late director thesis, Philippe Smets, the founder of IRIDIA, was working on an extension of such a belief function theory (or theory of evidence).

How would it affect the first few steps of the UDA if there were no defined probability for arriving in, say, Washington vs Moscow?

Well, in that case, there are probability measure. In the infinite self-duplication, you can even use the usual gaussian. But even if there were no such distribution, the result remains unchanged: physics becomes a calculus of first person uncertainty with or without probability. As I said, only the invariance of that uncertainty calculus matter for the proof of the reversal.

Tell me if this answer your question.

That seems to make sense. Thanks

OK. Ask any question in case you want grasp completely, or who knows, refute, the UDA argument. Please, for the step 8, MGA, use the most recent version which exists only on this list:



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