Re: The Case for Moderation

[Brent Meeker]

On 1/9/2025 2:37 AM, Quentin Anciaux wrote:
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.
If there were a causal mechanism then I could invoke it to eliminate, or 
at least reduce, the scope of randomness.

When you calculated probabilities during the Vietnam War, those 
calculations had predictive utility, but the unrealized scenarios were 
not part of reality
Sure they were.  More often than not I was calculating probabilities 
that were so small they wouldn't happen.  That's the whole point of 
relaibility calculations.  You show that failures are unlikely.

—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.
Every probability has the same grounding in the initial conditions and 
Schroedinger's equation.  That you experience one of them is what the 
probabilities predict.

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.
And all the other worlds are irrelevant.

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.
They have exactly the same causal antecedents as the one world that is 
realized.  Those antecedents are what went into the Schroedinger 
equation as initial conditions.  But Schroedinger's equation then only 
predict probabilities for the final conditions.

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.

Well I can't talk you out of feelings.  But don't send any relief funds 
to other worlds.

Brent



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
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