A prediction is validated by two things: a future event (the actualmeasurement whose result is required to confirm the prediction) and the right past choice(that makes possible the prediction).

Stapp’s argument does not demonstrate nonlocality because that choice of what to mea-sure on the left alters no thing on the right — i.e. it is “not a mechanical disturbance.”What it does alter is what we can meaningfully say about events on the right — i.e. it is aninfluence on the conditions that permit us to make a meaningful counterfactual statement.

n deny-ing the existence of a “mechanical disturbance” while maintaining the existence of an “influ-ence” Bohr is in no way asserting the presence of a mysterious non-mechanical disturbance(“quantum nonlocality”)

But that choice on the left does have an influence on thecondition that defines the very meaning of counterfactual statements about what mighthave happened earlier on the right.

The correlations in the outcomes of the four possible pairs ofmeasurements are encapsulated in the two-particle state, given (to within a normalizationconstant) by|Ψ〉 = |L1+, R1−〉 − |L2−, R2+〉 〈L2−, R2 + |L1+, R1−〉. (1)Here a state such as |L1+, R1−〉 indicates a simultaneous eigenstate of the commutingobservables L1 and R1 with eigenvalue + on the left and − on the right

My interest here is inthe remarkable way Bohr’s critique of EPR is clarified by applying it to Stapp’s argument

I point out thatthe reasoning leading to this conclusion relies on an essential ambiguityregarding the meaning of the expression “statement that refers only tophenomena confined to an earlier time” when such a statement containscounterfactual conditionals

The meaning of Bohr’s argument has been much debated. Mermin citesPlotnitsky’s book7 for a “thoughtful critique of Bell’s statements about Bohr’sviews”. Plotnitsky roundly condemns Bell as completely failing to under-stand Bohr. Bell himself admits to not understanding Bohr’s argument, butwith the implication that Bohr’s argument does not make sense

to those have difficulty understanding Bohr’s reply

I agree that “the Hardy-based analysis fortifies Bohr’sposition” [p. 7, Abstract], but only because it makes one take seriously the urgent need tofind a flaw in the apparently cogent reasoning of EPR

Whether Bohr knew in his bones that there were no elements of reality

10. Lucien Hardy and John Bell before him fatally undermine the position of EPR.

what I (but not Stapp) believe to be the nature of Bohr’sreply to EPR

A) Unlike Bell's theorem, the GHZ argument is based on unverifiedassumptions concerning the physical reality of a particular state vector andmeasurability of certain Hermitian operators pertaining to a system of threecorrelated spin-(l/2) particles.B) Unlike Bell's theorem, the GHZ formulation is limited to determinis-tic local theories.C) A direct experimental test of the GHZ argument is probably imposs-ible.

But in theclassical domain it is always possible to assign a priori well-defined values to allobservable quantities. This result of Garg and Mermin is disturbing for thecoherence and rationality of the existing quantum theory, which seems toextend its (~magic,) predictions also to the macroscopic domain where classicalphysics had successfully banished all <(magicab) approaches

Other interesting consequences of local realism were found by Garg andMermin[61] who were able to deduce Bell-type inequalities for two spin-jparticles (with arbitrary j). They could show that the singlet state for twoparticles with spin j leads to violations of local realism for arbitrarily largevalues of j right up and above the threshold of the classical world

We disagree with the contention by Mermin [46] that the GHZ formulation(ds an altogether more powerful refutation of the existence of elements ofreality than the one provided by Bell's theorem~. The reasons are, first of allthat one can talk of refutation only after an unambiguous experimental verdict,and moreover