"The Self-Sampling Assumption (SSA) [is] the idea that you should reason as if you were a random sample form the set of all observers" (Definition by Nick Bostrom)

Jacques Mallah I have argued numerous times on this everything-list that "quantum immortality" is NOT implied by the MWI. (e.g http://www.escribe.com/science/theory/msg00287.html, http://www.escribe.com/science/theory/msg00306.html, http://www.escribe.com/science/theory/msg00313.html, http://www.escribe.com/science/theory/msg00349.html, etc.)

The basic arguments are very simple. The predictions of the MWI are very clearly no different from the predictions of a one world interpretation in an infinite universe. (Cosmological predictions are a little more interesting but I'll get to that below.) It's true that in a one world universe, the probability of me surviving to 2100 is very low. But if I find myself in that year, that's no argument for the MWI, because the fraction of observers who have lived that long is no larger in the MWI. In either case I just got 'lucky'; the effective probability distribution in the MWI is proportional to the measure distribution which is heavily weighted toward shorter lifetimes. (Note to Don Page: what I call measure, you called quantum measure x number of observers.) Note also that if one believes that the MWI does imply immortality for the average observer, then it would be a disproof of the MWI, because we don't seem to be drawn from an immortal distribution of effective probability, but rather from the usual distribution of lifetimes which merely has a long time tail that decays.

Russell Standish I believe a fatal flaw in Jacques' and Don's arguments lies in assuming that every conscious moment must be drawn from some a priori distribution of such general conscious moments (Self Sampling Assumption). I think that this can only apply to the observation of one's birth order. The world that one observes must actually be conditional on the fact that you are born on your actual birthdate, and on the amount of time that has elapsed since then. Because my current age is less than the mean human lifetime, I can say that I'm currently living in a typical time. However (assuming the validity of QTI, which I do), if I find my self much much older than the mean human lifetime, then I must be living in an atypical world. This world may also be one in which homo sapiens far exceeds the usual species lifetime (assuming there is such a value). It will probably also be one in which evolution has largely stopped.

Jacques Mallah You are correct that we use the "SSA" or Copernican Anthropic Principle (CAP), but I can see no reason why you'd think it would only apply to birth order. Nor do I see any alternative to the CAP consistent with computationalism. I've explained this stuff to you guys umpteen times. The only new thing is that perhaps Don Page's conversion will motivate you to take another look, so go back and read what I've been saying. Observations of surviving a suicide attempt are of small measure, atypical. The fraction of observers like that is small, both at a given time and over all time. This is true if there are 10^9 people and it's true if there are infinitely many worlds each with copies of the 10^9.

Russell Standish Yes, I know you have explained your position many times, and each time I've read such a post from you, I have thought that your argument is flawed. Essentially, I suspect that you do not see the difference between Bruno Marchal's first person picture, and his third person picture. It is related to (but not equivalent to) the supposed paradox of free will, which comes from a distinction between Max Tegmark's bird and frog pictures. I somewhat despair that anything I can say could convince you, or vice versa, and that we waste a lot of time on unproductive things.

Jacques Mallah If the two 'pictures' give conflicting predictions, one of them is wrong. In special relativity, for example, is well that many things depend on what coordinate system you use; but predictions of what a given observer will observe are invariant. If it was not so, the theory would make no sense.

Russell Standish And that is true in this case too. Each observer will see a different distribution of lifetimes for their own lifetime (the first person picture), than they will for everyone else's (the third person picture). There is no conflict here.

Jacques Mallah So according to your statement, the predictions of a theory depend on which 'picture' you use. That is nonsense.

Russell Standish It is hardly nonsense. The predictions can easily depend of the 'picture' but must be consistent with each other. Let me give a simple example: In one picture, observer A decides to measure the spin of an electron in the x direction. In the other, observer B decides to measure the spin of the electron in the y direction. Observer A will see the spin of the electron aligned with x axis, and Observer B will see it aligned with the y axis. Both observations are correct in the first person picture of that observer. A "person" with the third person perspective, sees observers A and B as inhabiting separate `worlds' of a multiverse, each with appropriate measure that can be computed from Quantum Mechanics.

Jacques Mallah On the contrary, this is a textbook example of the way I said it works. The theory predicts some measure distribution of observers; an individual observer sees an observation drawn from that distribution. There are no different sets of predictions for different pictures, just the measure distribution and the sample from it.

Russell Standish It sounds to me like you don't think the prediction changes according to what the observer chooses to observe? An electron cannot have its spin aligned with the x axis and the y axis at the same time. Once the experimenter has chosen which direction to measure the spin, the history of that particular is observer is constrained by that fact, and the predictions of QM altered accordingly. This is true both in MWI and the Copenhagen interpretation, and is the "spooky" nature of QM. I used to think that QM gave predictions in terms of distributions, and that because one didn't see isolated particles, rather ensembles of such particles, I didn't see a problem. The properties of an ensemble are well defined. However, the ability of experimenters to isolate a single particle, such as a photon, or an atom, means we have to take this "spookiness" seriously.

James Higgo For anyone else, the sight of a billion-year-old man would not prove or disprove the Quantum Theory of Immortality. But for you, at age 1 billion, the probability that you would reach a billion, given QTI, is one. And the probability that you would reach a billion given not-QTI is very tiny. So it is not unreasonable to believe QTI. I'm not sure you can really quantify this.

Jacques Mallah And there's the proof of my above statement. Wei Dai has previously argued that the 'quantum suicide' crowd really just had a weird sense of morality regarding measure, rather than a wrong view of the math. I think the above proves that not to be the case: since Higgo now thinks that being old would be evidence of QTI, that proves that he does believe that the predictions of QTI would not be the standard predictions of QM as Wei and I understand it. I find it incredible that Higgo can state that being old would be statistical evidence for QTI, since one would not expect that without QTI, but still not realize that being young is statistical evidence against it.

Gilles Henri Jacques, I agree with James.

1) If you find yourself very old, this is no rigorous evidence for any theory. However you should choose the explanation following the maximum of likelihood criterion, i.e. the theory in which the probability of being very old in some world is maximum. This probability if 1 in MWI, and very tiny in conventional QM. So the fact of being very old should be considered as a very strong, although not absolute, evidence for MWI. In the same way, the thousands of experimental confirmations of QM are very strong pieces of evidence for QM, but not rigorous proofs (which do not exist).

2) Predictions of MWI, and thus QTI, are NOT the same as with standard QM. They are very close to it as long as you restrict yourself to events which you are actually surviving, which is the case of all known experimental confirmations of QM of course.

3) The fact of being young is not a statistical evidence against QTI, because the number (or the measure) of worlds where you are young is actually much larger than that where you are old. If you choose randomly a point between the x axis and the exponential curve y=exp(-x), most of your points will lie at x of the order of 1, although there exist an infinite number of points with x as large as you want. If you think that being young is statistical evidence against it, you should also think that your existing is a statistical evidence against MWI, because the measure of worlds where you do not exist is much larger.

James Higgo Furthermore, Jacques does not say what 'old' is. In relation to immortality, 31 is neither old nor young; in the same way, in relation to infinity, 31 is neither a lot nor a little, any more than 457*10E900 is a lot or a little.