Bruce, Let’s take your own argument about probability and push it to its logical conclusion. You said that if something with a 30% probability doesn’t happen in a given set of trials, that just means the prior probability estimate was wrong. Fine. Now, let’s apply that logic to a real-world scenario.
Imagine an asteroid is heading toward Earth, and based on all available data, models predict it has an 80% probability of impact. Yet, somehow, it doesn’t hit. By your reasoning, this means that the 80% estimate must have been wrong—because in the single-history universe, only what actually happens matters. The probability was just a number assigned to something that never had any reality. But this raises an obvious problem: what is probability even describing in a single-history framework? If probabilities are supposed to quantify real possibilities, yet some of them never happen despite high probability assignments, then those probabilities were meaningless from the start. The asteroid example makes it clear—if a highly probable event doesn’t occur, it wasn’t a real possibility in any meaningful sense. It was just a mathematical expectation that reality never fulfilled. In a multiverse framework, this isn’t an issue because the probabilities describe actual distributions of events across different branches. There exist branches where the asteroid hits and others where it doesn’t, and the 80% probability corresponds to the fraction of branches where impact occurs. But in a single-history framework, that 80% was just an empty number—nothing ever "happened" with 80% likelihood because only one outcome was ever real. Your argument boils down to saying, "Probability theory tells us what we should expect, but if reality doesn’t match, then the prior probability was wrong." But this means probability has no independent explanatory power—it is just a bookkeeping trick that retroactively adjusts itself to match what already happened. That’s not an actual explanation of events; it’s just a way of pretending probability still means something when it clearly doesn’t in a single-history world. So tell me: in a single-history universe, if the asteroid doesn’t hit despite an 80% probability, was it ever actually an 80% chance event? Or was that probability just an illusion, describing something that was never going to happen in the only history that exists? Quentin Le mer. 5 févr. 2025, 23:46, Bruce Kellett <[email protected]> a écrit : > On Thu, Feb 6, 2025 at 9:57 AM Quentin Anciaux <[email protected]> wrote: > >> Bruce, >> >> You’re trying to reduce the issue to my supposed "difficulty" with >> randomness, but that’s not the point. The problem isn’t whether quantum >> events are random—it’s whether probability has a meaningful foundation in a >> single-history universe where only one sequence of events is ever realized. >> >> You keep appealing to repeated trials, but even with infinite >> repetitions, some events with nonzero probability will never occur in the >> one and only history that unfolds. That’s not a minor detail—that’s a >> fundamental contradiction in the way probability is treated in a >> single-world framework. If an event assigned a 30% probability never >> happens, then its "probability" was meaningless in any real sense. It was >> never a real possibility, just a number in an equation. >> > > That is not a good argument. If something of supposed probability 30% does > not occur in,say, 100 trials, then your prior estimate of the probability > is wrong. Probability theory tells you how many occurrences of > low-probability events you can expect in a particular number of trials. If > those probability estimates are not fulfilled, then your prior probability > estimates are wrong. So it is wrong to say that low probability events will > never ccur, no matter how many trials you run. Probability theory tells you > what you can expect, and when low probability events can be expected to > occur (or not occur) in some sequence of trials. Many worlds theory can do > no better than this, because it says that you ill never see those low > probability branches, even if they exist. I don't see that this gets you > any further ahead. > > Now, regarding the Born rule: You claim that MWI contradicts it, but your >> argument assumes that every possible branch must exist in equal measure, >> which is not what MWI predicts. The structure of the wavefunction naturally >> leads to branches that reflect the Born probabilities because those >> branches are weighted according to the squared amplitudes. >> > > That is not true. If your theory, following Everett, is that the > Schrodinger equation is all that there is, then it is a fact that the > Schrodinger equation is insensitive to the coefficients, so branches do not > get weighted in the way you assume. IThe claim that branches are 'weighted' > by the coefficients is an additional assumption -- equivalent to the > assumption of the Born rule. > > It’s not about equal-counted branching—it’s about the distribution of >> measure across branches, which naturally results in Born-rule outcomes. >> > > That is something that has to be proved, and despite many efforts, it > still remains an unproven assumption. > > Your argument also ignores the fact that in a single-history universe, the >> Born rule is just an imposed rule with no deeper explanation. Why do >> probabilities follow this rule in a framework where only one history >> exists? What forces the realized history to match the expected distribution? >> > > Nothing 'forces' the realized history to match the Born rule expectations. > The Born rule is an observed fact, and it is an assumption of the theory > -- a brute fact about probabilities if you like. There is no deeper > explanation for random occurrences. > > If probabilities are just random assignments with no deeper foundation, >> then their success in predicting experimental results is equally mysterious >> in a single-history view. >> >> MWI provides an actual mechanism for why the Born rule emerges: it >> follows from the structure of the wavefunction itself. >> > > That is simply not true. You might like it to be the case, but it has > never been shown to be true. If it is true, you can give the proof here -- > physics would be delighted..... > > Your argument, on the other hand, assumes the Born rule as a brute fact >> without explaining why a single realized history should respect it in the >> first place. That’s not an explanation—it’s just asserting that the math >> works and ignoring the deeper implications. >> > > That is the way it is. The Born rule is just a brute fact, and since it is > a probability theory, there is no deeper 'mechanical' explanation. > > Bruce > > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion visit > https://groups.google.com/d/msgid/everything-list/CAFxXSLRyhs2d7wCGSJNRxoc_-zr4bLUJvbT53UPHiyGpHRmeDw%40mail.gmail.com > <https://groups.google.com/d/msgid/everything-list/CAFxXSLRyhs2d7wCGSJNRxoc_-zr4bLUJvbT53UPHiyGpHRmeDw%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. 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