Brent,

You're leaning heavily on the idea that probability is meaningful simply
because it's applied before knowing the outcome. But that doesn't address
the real problem: in a single-history world, probability isn’t describing
actual potentialities—it’s describing imagined ones that were never part of
reality. You claim that "they did have a chance of being real," but in a
framework where only one history ever unfolds, that’s just wordplay. They
never happened, and they never were going to happen, because the one
sequence of reality had already been determined.

You mock the idea of unobservable branches in MWI, but at least those
branches correspond to real structures in the wavefunction. In contrast,
your framework uses probabilities that refer to nothing but hypothetical
scenarios that never had any ontological status. You want probability to
describe "a chance," but in a single-history universe, those chances were
never real—they were just numbers assigned before the event, with no deeper
meaning beyond prediction.

Your card game example doesn’t help you. You ask what odds I’d give if my
opponent draws a 6 of Spades. Fine. But in a single-history world, only one
game will ever be played, and only one sequence of cards will ever be
drawn. No matter what probability I assign beforehand, if in this single
history I never draw a card higher than a 6, then those probabilities were
just empty formalism. They described something that never had a chance of
occurring because it never did and never would.

You dismiss MWI’s branches as "unobservable," yet you rely on equally
unobservable "chances" in a single-history world. The difference is that in
MWI, probabilities describe distributions over real branches, while in a
single-history world, probability is just a way of pretending that things
that never happened somehow mattered.

In short, your position requires believing that probability describes
possibilities that never existed and never will, yet somehow remain
meaningful. That’s incoherent. If probability is supposed to describe
reality, it needs something real to refer to—not just imagined alternatives
that were never anything more than numbers in an equation.

Quentin

Le jeu. 6 févr. 2025, 05:01, Brent Meeker <[email protected]> a écrit :

>
>
>
> On 2/5/2025 12:36 PM, Quentin Anciaux wrote:
>
> Brent,
>
> I went through the document you sent, and it outlines the different
> interpretations of probability: mathematical, physical symmetry, degree of
> belief, and empirical frequency. But none of these resolve the core issue
> in a single-history universe—where probability is supposed to describe
> "possibilities" that, in the end, never had any reality.
>
> "in the end" implies post-hoc judgement.  When you calculate and apply
> probabilities you don't know which events will be realized.  That's why
> they are probabilities.
>
>
> Your frequentist approach assumes that, given enough trials, outcomes will
> appear in proportions that match their theoretical probabilities.
>
> Which is why some philosophers of mathematics tried to define
> probabilities as long-run (-> infinity) frequencies.
>
> But in a finite, single-history universe, there is no guarantee that will
> ever happen.
>
> And there's no guarantee some possibility you've overlooked will occur.
> Forget histories.  Suppose your friend  has drawn a card, 6 of Spades, and
> now you're going to draw a card and high card wins.  What odds are you
> willing to give him?
>
> Some events with nonzero probability simply won’t occur—not because of
> statistical fluctuations, but because history only plays out one way. In
> that case, were those possibilities ever really possible? If something
> assigned a probability of 10% never happens in the actual course of the
> universe, then in what meaningful way was it ever a possibility?
>
> It's an application of a theory.  Of course it can be mis-applied.  You
> might leave out a possibility that actually happens.
>
>
> You argue that if all possibilities are realized, probability loses its
> meaning. But in a single-history world, probability is just as meaningless
> because it describes outcomes that never had a chance of being real.
>
> How is that different that describing outcomes that occur where nobody can
> check that they happened, that are, in your words, just abstractions.  And
> they did have a chance of being real, which you would realize if you knew
> what " a chance" means."
>
> If probability is supposed to quantify potential realities, then in a
> framework where only one reality exists, probability is nothing more than a
> retrospective justification—it has no actual explanatory power.
>
> The math remains internally consistent, but it becomes an empty formalism,
> detached from anything real.
>
> Don't take any money to a poker game.
>
> The whole structure relies on pretending that unrealized events still
> "exist" in some abstract sense,
>
> Which is better than pretending that whole unobservable, inaccessible
> really, really exist for real...they just don't make any difference to
> anything.
>
> Brent
>
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