Brent, The core disagreement here seems to rest on the role and status of possibilities. In a single-world framework, the unrealized possibilities you refer to have no actual existence or causal link to the realized world. They are simply conceptual tools to calculate probabilities. But this is precisely what strikes me as incoherent: why invoke these possibilities as part of the explanation if they play no real role in shaping the outcome?
You argue that they reduce the probability of occurrence for other events. But this reduction is purely formal—an artifact of the mathematical framework, not something grounded in reality. In a single-world view, only the realized history exists, so the "ensemble" of possibilities is entirely abstract. It doesn’t exist as part of reality, which means it cannot influence or interact with it. The "reduction of probability" you mention is simply a mathematical convenience, not a causal mechanism. When you calculated probabilities during the Vietnam War, those calculations had predictive utility, but the unrealized scenarios were not part of reality—they didn’t shape or explain the actual outcomes beyond being conceptual constructs. That’s fine for practical purposes, but when applied to the nature of existence itself, it becomes unsatisfying. The single-world framework uses the language of possibility and probability without giving these notions any real grounding. In a multiverse framework, possibilities are not just mathematical tools—they are ontologically real. Each possible outcome exists within the structure of the multiverse, and the probabilities describe the distribution of outcomes across this ensemble. This provides explanatory depth that the single-world framework lacks because it doesn’t need to rely on nonexistent possibilities to "explain" realized outcomes. Your bridge tournament analogy highlights the difference: in the single-world view, only one table exists, and all the other possible hands are irrelevant—they have no role in shaping the one game that’s played. In the multiverse view, all tables exist, and the hand you’re dealt corresponds to your position in the tournament. The probabilities describe the relative frequency of hands across the tables, not just the abstract chance of receiving one hand. The single-world framework asks us to accept that possibilities exist only in the abstract, with no causal or explanatory role in the realized world. This reliance on nonexistent entities to justify outcomes feels like an incomplete explanation, one that collapses into "it just happened this way." That’s the heart of my issue with it. Le jeu. 9 janv. 2025, 07:33, Brent Meeker <meekerbr...@gmail.com> a écrit : > > > > On 1/8/2025 9:42 PM, Quentin Anciaux wrote: > > Brent, > > The issue I see with a single-world framework is the reliance on > possibilities that have no existence or causal link to the realized world. > In this view, possibilities are entirely notional, they don’t exist > ontologically, and they have no impact on the single realized history. This > makes their invocation seem unnecessary, even absurd, because they don’t > contribute to the reality we observe in any meaningful way. > > But they do. They reduce its probability of occurence. > > > If the only thing that exists is the realized world, why appeal to a > theoretical ensemble of possibilities? > > Because that's what the equations of quantum mechanics produces. We're > not "appealing to them" where taking them into account as things that might > occur. That's why the Born rule assigns probabilities less than one to > them. > > It’s as if the single-world view borrows the language and tools of > probability to describe outcomes but discards the explanatory depth > provided by an actual ensemble. > > I'd say that's looking at it exactly backwards, as though the "tools of > probability" on applied to cases that were really deterministic (had > explanatory depth) and what work is done by the word "actual" in "actual > ensemble". Usually it is an ensemble of possibilities. When you're dealt > a bridge hand no one supposes that all other possible hands are dealt > somewhere else; it is enough that they merely possible. During the Viet > Nam was I calculated the probability of dropping a bridge with a Walleye, I > calculated the probability of a missile failure causing it to hit the > launching aircraft, I calculated the probability of a wayward missile going > out of the range safety boundaries, and dozens of other probabilities. I > was always considering a range of instances and their contrary; but I never > needed to suppose the instances were actually anything more than > possibilities. They didn't have to happen anywhere in any world. > > Without the existence of unrealized possibilities, the concept of > "randomness" seems like a placeholder for "it just happened this way," > offering no real insight into why this one history unfolded. > > No, it's a "placeholder" for it could have happened these other ways but > didn't. > > > In contrast, in a multiverse framework, the ensemble is not merely > theoretical, it has ontological status. > > Yes, it's like a bridge tournament in which all possible hands are dealt > at different tables and then you pick one to sit *at random*. But wait, > that's absurd, we must sit down at every table. And then we must play > every possible card in every possible order. Otherwise we cannot speak of > the probability of making our bid. > > The possibilities exist and have causal relationships within the broader > structure. This provides coherence to the use of probability, as it > describes the distribution of outcomes across the ensemble, not just within > a single, isolated history. > > The single-world framework effectively asks us to accept a universe where > unrealized possibilities are invoked to explain outcomes, yet they have no > actual role in shaping reality. > > Sure they do. If they are things that might possibily happen then they > reduce the probability of something else happening. > > Brent > > This reliance on something that neither exists nor affects the realized > world strikes me as deeply incoherent. > > Quentin > > Le jeu. 9 janv. 2025, 03:14, Brent Meeker <meekerbr...@gmail.com> a > écrit : > >> >> >> >> On 1/8/2025 4:11 AM, Quentin Anciaux wrote: >> >> Brent, >> >> The core of my argument is that in a single-world framework, the ensemble >> of possibilities described by Schrödinger’s equation is only conceptual. If >> only one history is realized, then those "possibilities" don’t exist in any >> meaningful way—they’re theoretical abstractions. In the absence of an >> actual ensemble from which a selection occurs, the notion of randomness is >> a metaphor, not a mechanism. >> >> In the many-worlds framework, every possibility is realized, so the >> "selection" is an emergent phenomenon from within the structure of the >> totality. In the single-world view, however, there’s no actual ensemble. >> Probabilities merely describe the likelihood of the one realized outcome, >> but there’s no underlying framework where those possibilities are >> instantiated. Randomness then becomes a label for the lack of explanation >> rather than a true process. >> >> To say "the single history simply is" and call that random doesn’t >> resolve the issue—it just restates it. Without an ensemble that exists >> ontologically (even probabilistically), the idea of selection collapses >> because there’s nothing to select from. The photon emission you mentioned >> is described by probabilities in QM, but those probabilities don’t >> correspond to real, alternate outcomes in a single-world framework. The >> realized outcome is the only one that exists, and all other "possibilities" >> are simply unrealized ideas. >> >> In contrast, in the many-worlds interpretation, the photon’s emission in >> one state is one thread of the total structure, and alternate emissions >> exist along other threads. This gives explanatory power to the >> probabilities, as they correspond to real structures within the ensemble. >> >> But small probabilities explain why things *don't* exist. >> >> >> Regarding your point that probabilities lose meaning in MWI because all >> possibilities are realized—that’s not the case. Probabilities in MWI are >> understood as the measure of the branching structure relative to the >> observer's perspective. They still hold meaning because they reflect the >> structure of the multiverse, not a singular outcome. >> >> What about the one's for which P=0, you could as well say that reflect >> the structure of the multiverse. Will you make an ensemble of them? >> >> >> The single-world view still strikes me as incoherent because it leans on >> the language of probability and possibility but denies their actual >> realization. Without an ensemble, it’s hard to see what randomness truly >> means. >> >> In every other application of probability theory (and for years I headed >> the Reliability Division at Pt. Mugu) the ensemble is only notional. It is >> a the set of possibilities without assuming that they exist, in which case >> they would be actualities. With an ensemble of which every member exists, >> randomness becomes incoherent. >> >> Brent >> -- >> 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 everything-list+unsubscr...@googlegroups.com. >> To view this discussion visit >> https://groups.google.com/d/msgid/everything-list/207aada7-2a8d-4c9e-8490-a25f23eff83a%40gmail.com >> <https://groups.google.com/d/msgid/everything-list/207aada7-2a8d-4c9e-8490-a25f23eff83a%40gmail.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 everything-list+unsubscr...@googlegroups.com. > To view this discussion visit > https://groups.google.com/d/msgid/everything-list/CAMW2kAoJKWzYSjXeRQJCNBiXo2Xbk8VseggxV%3D6rgWL4y6aMFQ%40mail.gmail.com > <https://groups.google.com/d/msgid/everything-list/CAMW2kAoJKWzYSjXeRQJCNBiXo2Xbk8VseggxV%3D6rgWL4y6aMFQ%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 everything-list+unsubscr...@googlegroups.com. > To view this discussion visit > https://groups.google.com/d/msgid/everything-list/2f860f70-c8af-477a-add2-c7192ab54ed2%40gmail.com > <https://groups.google.com/d/msgid/everything-list/2f860f70-c8af-477a-add2-c7192ab54ed2%40gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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