Seems to me a good summary đ Le jeu. 9 janv. 2025, 11:33, PGC <[email protected]> a Ă©crit :
> This is getting circular. Brentâs single-world view treats the > wavefunction âŁÎšâ©=âiâαiââŁÏiââ© as purely instrumental: it calculates > probabilities for each outcome, but in the end only one outcome (âŁÏkââ©) > âactually happens.â Everything else is declared ânot real.â This works fine > for making predictions, yet offers no deeper reason why all other âŁÏjââ© ( > jî =k) must be forcibly nullified. One must simply accept that, by some > extra postulate or interpretation, the other possibilities vanish. > > Quentinâs many-worlds (or âall possibilities realizedâ) approach skips > that forced collapse. Instead of removing alternate terms, it treats each > âŁÏjââ© as persisting in a branching global state. The ârandomnessâ we see > is then about which branch âweâ (as observers) occupy, rather than an > inexplicable destruction of non-selected outcomes. So thereâs no logical > step that says, âEverything else is disallowedâ; itâs all there in the > broader superposition. Probabilities emerge from relative measures of those > branches rather than from an unexplained single selection. > > In short, Brentâs stance is instrumentally consistent but depends on an > unelaborated principle that kills off every competing outcome. Quentinâs > stance avoids such ânegationâ by allowing all terms of the wavefunction to > proceed. Whether thatâs too big an ontological leap is a separate > debateâbut it at least doesnât require a special rule that says, âOnly one > of these can exist; the rest never happened.â Brent, you're asking for > "extra negation", pretending that you simplify when in fact, you add a > whole new assumption. Similar to atheists who need to use the notion of god > to assert ~god, thinking rather simplistically that you've cleaned up the > whole mess. > > On Thursday, January 9, 2025 at 7:33:49âŻAM UTC+1 Brent Meeker wrote: > >> >> >> >> 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 donât exist >> ontologically, and they have no impact on the single realized history. This >> makes their invocation seem unnecessary, even absurd, because they donât >> 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. >> >> >> Itâs 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 <[email protected]> a Ă©crit : >> >>> >>> >>> >>> 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 Schrödingerâs equation is only >>> conceptual. If only one history is realized, then those "possibilities" >>> donât exist in any meaningful wayâtheyâre 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, thereâs no actual ensemble. >>> Probabilities merely describe the likelihood of the one realized outcome, >>> but thereâs 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 doesnât >>> resolve the issueâit just restates it. Without an ensemble that exists >>> ontologically (even probabilistically), the idea of selection collapses >>> because thereâs nothing to select from. The photon emission you mentioned >>> is described by probabilities in QM, but those probabilities donât >>> 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 photonâs 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 realizedâthatâs 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, itâs 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 [email protected]. >>> 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 [email protected]. >> >> 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 [email protected]. > To view this discussion visit > https://groups.google.com/d/msgid/everything-list/46944e8d-73e2-4e0c-8a15-d1c43a7cc9bfn%40googlegroups.com > <https://groups.google.com/d/msgid/everything-list/46944e8d-73e2-4e0c-8a15-d1c43a7cc9bfn%40googlegroups.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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