[codethief]

I might not be using the same definitions as you are or maybe I'm getting something mixed up, so I'd be glad if you could elaborate on what exactly you mean by "determinism", "realism" and especially "locality".

(In my book, the Copenhagen interpretation is a non-realistic(∆), non-deterministic and local theory, which would contradict your statement.)

(∆) Assuming, of course, that the wave function is not an object of reality, as I think is standard.

[tezthenerd]

Many would argue that Copenhagen is not local, but its very hard to even define locality if you are genuinely non-realist about everything.

Regardless, if it was possible to be "local + non-deterministic" many of us would be fine with that. But its not - Bell rules out "locality + realism", regardless of whether the realistic theory is deterministic or non-deterministic.

[codethief]

> Many would argue that Copenhagen is not local

Who? I believe the point of view that the Copenhagen interpretation is local is the standard one.[1]

> but its very hard to even define locality

How so? There are various definitions of locality—in terms of no faster-than-light transmission of information, in terms of commutators of field operators at spacelike distances vanishing as well as in terms of C* algebras—and the Copenhagen interpretation fulfills them all.

> if you are genuinely non-realist about everything

I'm being non-realist only about things whose existence we can't prove, e.g. the wave function.

> Regardless, if it was possible to be "local + non-deterministic" many of us would be fine with that. But its not - Bell rules out "locality + realism"

I don't see how this disproves anything of what I said. While I think you're right[2] about the fact that the violation of Bell's inequality rules out local realism—irrespective of determinism—, I already said that, in my book, Copenhagen is not a realistic theory because the wave function is not an object of reality.

[1]: https://en.wikipedia.org/wiki/Principle_of_locality#Copenhag...

[2]: "However, Fine's theorem shows that, this deterministic assignment of properties is not required to prove Bell's theorem. This is because the set of statistical distributions for measurements on two parties, once locality has been assumed, are independent of whether or not determinism is also assumed." (https://en.wikipedia.org/wiki/Principle_of_locality#Local_re...)

[codethief]

s/realistic/realist, sorry for the typo.

[testvox]

Don't throw out realism so easily. Ending the quest for answers by invoking mysticism is very easy for people to do but its never the right answer. https://www.lesswrong.com/s/5uZQHpecjn7955faL/p/6i3zToomS86o...

[codethief]

Where did I invoke mysticism? And where did I end the quest for answers?

I said "in my book" for a reason. You might of course argue that the wave function is real, which would make the Copenhagen interpretation a realistic, albeit non-local theory (as the collapse of the wave function would happen instantaneously everywhere). I'd be very happy to discuss this but please bear in mind that this was not what the discussion was about.