[jostylr]

For non-relativistic QM, the QM formalism is provable from Bohmian mechanics, an actual particle theory. BM starts from particles have locations the change continuously in time via a guidance equation using the wave function of the universe. One may choose other theories to explain quantum phenomena, but to say "There is simply no physical machinery to support an objective reality, period." is just false, at least in that realm. As for relativistic QFT, there are plausible pathways using Bohmian ideas as well though nothing as definitive as BM has been firmly established.

I would also say that any theory that does not have room to say definitively that I exist is a theory that is obviously contradictory to my experience and is therefore falsified. There has to be room in the theory for at least me. Additionally, I would certainly value much more a theory that has room for the rest of humanity more than one which questions the existence of everyone but me. I am not even sure what the point of a theory would be if it could not account for collaborative science being done.

[d4rkn0d3z]

QM does not deny you existence, it rather denies you a complete objective description of how you exist. Or perhaps it says that your existence is not an objective phenomena.

[fellowniusmonk]

Would you mind clarifying in which of these 3 dictionary definitions of the word objective my existence (in the sense of the "particles" of my body) is not objective? Or maybe these definitions are not exhaustive? Perhapse the term objective has become overloaded.

objective

adjective

Not influenced by personal feelings or opinions when considering and representing facts; impartial. “Historians try to be objective and impartial.” Synonyms: impartial, unbiased, neutral, dispassionate, detached. Antonyms: biased, partial, prejudiced.

Existing independently of the mind; actual. “A matter of objective fact.” Synonyms: factual, real, empirical, verifiable. Antonym: subjective.

Grammar. Relating to the case of nouns and pronouns used as the object of a transitive verb or a preposition.

[n4r9]

BM is objective, and indeed deterministic. I'm not exactly sure what you mean by "complete" but it has all the same predictions as other interpretations of QM. It has some odd quirks however, such as explicit non-locality.

[jostylr]

Since EPR+Bell showed that nature is non-local, it is a feature, not a bug, to be explicit about how non-locality happens. Collapse theories are also explicitly non-local.

[n4r9]

That's one position in a century-long debate. But there are other assumptions than locality in the proof of Bell's Theorem, which other interpretations of QM relax. Like having single measurement outcomes (many-worlds), or observer-independent states (QBism).

[jostylr]

In terms of quirkiness, how would you rank them? I feel like nonlocality is far less quirkier than saying that all possible outcomes of a measurement happen even though we just see one. Also standard QM has the quirk of being nonlocal. So QM is just quirky.

[n4r9]

There are many that I don't understand very well, so I'm reluctant to rank them. My tendency is to be skeptical about how clearly us humans can see the underlying reality of things, so I find epistemic interpretations like QBism appealing on that basis.

The "every outcome happens" aspect of many worlds is a lot to accept. Otoh that's what you get if you take quantum states to be ontological and universal. My problem is more to do with how the Born rule falls out. There are some arguments for it based on decision theory, but I find the step from "this is how a rational betting agent maximises winnings" to "this is the objective probability of a scientific observation" uncompelling.

I'm not sure what you mean by "standard QM". There's the mathematical framework - which is effectively a way of calculating probabilities of measurement outcomes - and then there are interpretations, which assign ontological status to some/all of the mathematical objects. Non-locality properly applies to the latter, since you cannot say that the "real" physical state of a particle has changed until you've said which parts of the mathematics are real.

[d4rkn0d3z]

I don't at all begrudge you your logical predictive fictions.