Le 25-janv.-06, à 20:05, [EMAIL PROTECTED] a écrit :
In the UDA it is said that the Correct Level Of Substitution (I'll call is CLOS for short) is unknowable. I agree: Just intuitively, in a closed system, how could we know if something wasn't exactly right? It would result in the future being different than it would have been, but we wouldn't be aware of the difference. We would just accept that as reality.
But smoking a cigarette or drinking tea or things like that also result in the future being different, and in those case many will still say they did survive the cigarette, tea, ... And those possible different stories are of a type such that it is reasonable to say the CLOS (Correct Level of Substitution) has been chosen, despite you are right we cannot know it. More apt to share your intuition here would be "agnosic mental disease", where, for example, someone get blind after some use of (classical) teleportation, but get also amnesic relatively to everything concerning vision. He would say "I did perfectly survive" although we could have reasonable doubt it is so.
Since the CLOS is unknowable, then we should be able to talk about an unknowable, yet true, probability P(CLOS) that each substitution is done at the CLOS.
I think it would be foolish to choose the LOS (the level of substitution) in any probabilistic way. Real doctors will argue for some level with argument from biology or physics. If he knows "comp" and its consequences, he will know that nothing can give certainty in this matter.
By the way, we know at least P(CLOS) < 1 because the doctor is guessing, ...
I could temporarily agree.
... and P(CLOS) = 1 would implies that the doctor knows and can actually implement it.
Not at all. Suppose some doctor choose the right level, which exists by comp. The doctor will not know it, as we already agree on that point. Still, platonistically P(CLOS) = 1. Look at this analogy: I give you a dice and ask to bet on the result you can get. You can tell me you will get six with probability = 1/6. *I* could know that the dice is unfair or corrupted, and that the real probability is, let us say 1/2. For the CLOS, nobody (even Gods) can know the real probability, but for the derivation of the LAWS of physics, we need just to compute the probability for all the CLOS, given that the Universal Dovetailer generates all your continuations at all correct levels, by construction.
OK, so now for my question. So when we talk about finding a probability measure on the 1-determinancy (I don't know if that's the exact right words),
I guess you were meaning 1-indeterminacy.
don't we have to multiply this probability measure by the unknown P(CLOS) to get the actual probability measure?
Sure. Except that nobody will ever computes those exact "actual probability measure". It would be like computing the weather probabilities by computing the Feynman Integral on all particles/waves of the planet earth together with the probabilities that Feynman got the right integral + the probability that I am not dreaming, etc. (this mix unfaithfully the different sorts of uncertainty).
But this would imply that the probability measure is impossible to find out to any degree that would be called scientific, since it is a function of P(CLOS), i.e. the step of faith in saying "Yes" to the doctor who doesn't know anything.
You are confusing perhaps two levels of uncertainties. The probability measure could be computable if comp is true. What is impossible is to know the probability are the correct one, except we can test this experimentally. We can still believe correctly in those probabilities, and this, for sure, without knowing we are correct. It is the same with physics. We cannot know for sure that QM is a or the correct theory, but this does not prevent us to bet on it, and then to use its probability theory. No serious scientist will take into account that QM could be false to change the probabilities implied by it. If QM makes a wrong prediction, QM will be refuted, nobody will correct it simply by multiplying the QM uncertainties by some higher level of epistemological uncertainty. I think.
In fact, if each moment is equivalent to a substitution (not necessarily at the CLOS!), as comp says, then there would be an exponential decay of our identity, as sort of identity entropy.
Sure. That's almost a proof "by the absurd", that we should be very careful before mixing type of uncertainty. Remember that the goal will not even consist in deriving some tools for computing the comp proba, but consists in deriving the mathematical structure of those comp-proba, so as to compare them with the empirical QM proba.
Bruno http://iridia.ulb.ac.be/~marchal/
