In re-discussing the EPR scenario in his autobiographical notes (1946), Einstein wrote:
What Bell did
The first option (i.e. "telepathically changes the real situation") is just Einstein's unacceptability of non-locality as it goes against relativity but what does Einstein exactly mean by his unacceptability of the second option: "denying independent real situations as such to things which are spatially separated from each other"? Wiseman in one paper has suggested that what Einstein means by the second option is "extreme subjectivism", denying that there are matters of fact about distant observers:One can escape from this conclusion [that statistical quantum theory is incomplete] only by either assuming that the measurement of S1 (telepathically) changes the real situation of S2 or by denying independent real situations as such to things which are spatially separated from each other. Both alternatives appear to me equally unacceptable.
Maudlin also discusses this second of Einstein's options but appears more non-committal to it, especially given that he feels it leaves Einstein's argument for the incompleteness of QM untouched:Statistical QM as a theory with a single observer A allows ψ to be interpreted as A’s knowledge of the quantum world. The fact that this changes instantaneously now poses no mystery, because it is merely a change in A’s knowledge. But precisely because it is only a change in A’s knowledge, this change in ψ cannot affect the result B obtains, even when (as with the EPR state) the results that A and B obtain may be perfectly correlated. Statistical QM as a theory of A’s knowledge evades this problem, however, simply by denying that B has an independent existence. All that exists (if the theory is complete) is A’s knowledge of B.
Is it accurate to say, that if we accept this second option of non-realism in Bell's scenarios, does it mean a more radical non-realism as argued by Wiseman:In this passage Einstein offers two possible ways to reject the conclusion of his argument: accept telepathy or reject the claim that systems spatially separated from one another even have ‘independent real situations’. Unfortunately, Einstein never discusses this second option in detail. My guess is that Einstein couldn’t even really imagine what this second option could be like. But more than that, it is not even clear to me exactly how this move is supposed to interfere with the argument. If we use the EPR criterion of an element of reality, then we get the existence of an element of reality in S2 that was not represented in the quantum mechanical description of S2, so the quantum-mechanical description is not complete.
From Einstein’s Theorem to Bell’s Theorem: A History of Quantum NonlocalityOn the other hand, if one assumes that relativity is fundamental, then Bell experiments have proven that there is no real world. To be more precise, under this assumption Bell-experiments have proven that the real world exists only within one’s own past light-cone. It cannot be stressed enough that this does not mean merely that microscopic particles or fields cannot have determinite properties. It means macroscopic objects, other conscious observers even, are not real at the present time.
What Bell did