On 2/5/2025 11:44 PM, Quentin Anciaux wrote:
Bruce,
You keep insisting that randomness "just is" and that no deeper
explanation is possible, but that’s precisely the problem with the
single-history view: it reduces probability to a descriptive
afterthought with no fundamental meaning. You argue that in a
single-history universe, we must simply accept that an event had an
80% chance of happening even if it never does.
You're making up strawmen. If it never does in many trials, then it's
simple Bayesian calculation to tell you it's much more */probable/* your
80% value contains an error than not. You've obviously never dealt with
the actual application of probabilities.
But in what sense was that probability real if only one history ever
unfolds and the event never occurs?
You say that probabilities are "real enough" because they are based on
prior experience. But prior experience in a single-history universe is
just another way of saying, "this is what happened before." That’s not
an explanation; it’s circular reasoning.
No, it's the most basic form of prediction from statistics.
You’re using past outcomes to justify probability assignments, but if
probability is supposed to describe potential events, then what does
it mean when a "possible" event never happens, despite being assigned
a nonzero probability?
You keep harping on "it never happens". Bruce and I have both addressed
that. It you toss a coin twice and "it never happens" to come up
tails. If you toss it a thousand times and it never comes up tails,
it's a two-headed coin.
In a multiverse framework, probability describes the relative
frequency of events across actualized branches.
You keep using the word "actualized" which according to my dictionary
mean "made actual". But that's false. The branches are just what, in
another context, you characterize as mere abstract mathematices.
It is not just an abstract expectation—it is grounded in the structure
of the wavefunction itself.
Which itself is an abstraction, an abstraction that does not even
include probabilities.
You dismiss the idea that measure in the wavefunction corresponds to
probability, but this is not an assumption—it follows naturally from
the mathematics of quantum mechanics. The Born rule is not an extra
assumption in MWI; it emerges from decision theory (Deutsch-Wallace),
from symmetry arguments (Zurek’s envariance), or from self-locating
uncertainty. You keep demanding "proof,"
It's not just me. People have been searching for a way derive the Born
rule for decades and in every case so far the derivation have been found
to assume things equivalent to assuming the Born rule. And that goes for
Deutsch and Wallace. Zurek doesn't even pretend to derive it, he just
asserts that it must work such that only the Born rule probabilities
apply to stable worlds. Read the literature.
yet you accept the Born rule as a brute fact in your own framework
without any justification beyond "that’s just how quantum mechanics
works."
That's why physics is an empirical science. Some things are derived
from observation, not "self evident axioms".
Meanwhile, your single-history approach provides no mechanism for why
probabilities match experimental results.
Do you think MWI would be true even it didn't match experimental results??
You claim that probability "just works" without explaining why the
realized history should respect the Born distribution at all. You
dismiss branch weighting in MWI as unproven, yet you offer no
competing explanation for why a single sequence of events should
follow probabilistic predictions.
Ultimately, your position amounts to: "Random events happen,
probabilities just work, and there’s no deeper reason for anything."
That seems to the case for QM. It may anger you or disappoint you, but
Nature doesn't care about your demands.
That’s not an explanation—it’s an assertion that we shouldn’t ask
questions. If you’re satisfied with that, fine, but let’s not pretend
it’s a superior foundation for probability. It’s just giving up on
understanding why reality follows probabilistic laws in the first place.
I'm fine with asking questions. I'd be fine with finding way to derive
Born's rule without assuming it or something equivalent. What I'm not
fine with is inventing imaginary world's and claiming that's the same thing.
Brent
Quentin
Le jeu. 6 févr. 2025, 01:09, Bruce Kellett <[email protected]> a
écrit :
On Thu, Feb 6, 2025 at 11:49 AM Quentin Anciaux
<[email protected]> wrote:
Bruce,
You’re making a distinction between single-event probabilities
and repeated trials, but you’re not addressing the core issue:
in a single-history universe, probability is only ever
descriptive, not explanatory. You claim that if an asteroid
has an 80% chance of impact but doesn’t hit, then the 20%
chance was simply realized. But this explanation is entirely
retrospective—it tells us nothing about why this history,
rather than any other, is the one that unfolded.
That is the nature of random events. It seems that your real
objection is to randomness, events that have no simple mechanical
explanation. That is quantum mechanics, and you just have to get
used to it.
You say, "assuming the calculations were accurate, then there
certainly was an 80% chance of hitting, and a 20% chance of
missing." But in what sense was that 80% ever real? In the
only history that exists, the asteroid never had an 80% chance
of hitting—it always had a 100% chance of missing because
that’s what happened. The probability was just a number
assigned before the event, with no actual force in determining
the outcome.
I think the calculations are based on prior experience. They are
real enough, not just empty air.
In a multiverse framework, probabilities are grounded in
actual distributions across histories. The 80% means that in
80% of branches, the asteroid hits, and in 20%, it misses.
This gives probability an explanatory role—it describes the
structure of reality, not just an arbitrary number assigned to
something that never had a chance of happening.
Unfortunately, it is well known that branch counting is a failed
enterprise in quantum mechanics. So the claim that something or
the other is true in 80% of the branches is just empty rhetoric.
You claim that MWI has no way to connect probabilities to the
wavefunction, but that’s false. The structure of the
wavefunction naturally assigns measure to branches,
Does it now? And how does it do that? You have a well-developed
ability to make endless unevidenced assumptions and bend them to
your will. Start trying to prove some of this!
and those measures correspond to the squared amplitudes of the
coefficients—the Born rule emerges from this structure.
It does not without many additional assumptions. The attempts to
derive the Born rule from Everett have all failed.
You keep asserting that probabilities in MWI are meaningless
because "all possibilities happen," but that’s only true if
you ignore the fact that measure matters. Not all branches are
weighted equally, and the frequencies of outcomes reflect
those weights.
But you have not shown how these weights arise, or how outcomes
depend on these 'weights'.
The issue isn’t whether we can calculate probabilities in a
single-history world—it’s whether those probabilities have any
real ontological meaning. You claim that in a single-history
world, probabilities "just work," but that’s not an
explanation. It’s just a way of pretending that numbers
assigned before an event have some deeper reality when, in
truth, they don’t. In the end, the only thing that exists is
the one history that happens, and everything else was just an
illusion of possibility.
You are still looking for an 'explanation' of random events. You
will look in vain, because no such explanation can be forthcoming.
Bruce
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