Explaining Bell's Local Realism

Opinions vary widely on Bell's Theorem.

From a recent Italian paper:

In a lecture held in 1983, Richard Feynman argued that the Bell theorem “is not a theorem that anybody thinks is of any particular importance. We who use quantum mechanics have been using it all the time. It is not an important theorem. It is simply a statement of something that we know is true – a mathematical proof of it.” (quoted in Whitaker 2016b, 493): in Feynman’s view, what ‘we know is true’ is simply that quantum theory is not a classical theory. No matter what is the tenability of the Feynman charge of irrelevance about the Bell theorem, a common view of what it takes for a physical theory to be ‘classical’ is that the physical systems the theory is about can be assumed to have measurement- independent properties or, in other terms, that – in the well-specified situations that are suitable for physical investigation – these physical systems can be assumed to have pre- existing values for all relevant quantities, values that the measurement is supposed just to reveal. In this vein, ‘classicality’ is thus equated more othen than not with a loose notion of ‘realism’.

I agree with this. Bell's theorem is just a way of saying that quantum mechanics is not a classical theory, and that had been everyone's understanding since about 1930.

All of this would be non-controversial except that Bell started convincing people that what he really proved was that quantum mechanics violated local realism, whatever that is. Physicists were willing to give up classicality, not not realism.

It is all verbal trickery. Realism does not mean anything useful. Read the paper for details.