Hidden Variables in Quantum Mechanics Reconsidered

J. S. Bell

The demonstrations of von Neumann and others, that quantum mechanics does not permit a hidden variable interpretation, are reconsidered. It is shown that their essential axioms are unreasonable. It is urged that in further examination of this problem an interesting axiom would be that mutually distant systems are independent of one another.

Simon Kochen, Ernst P. Specker

Simon Kochen, Ernst P. Specker

Marlan O. Scully

Milonni reconsiders our recent work based on a singlet spin-\textonehalf{} system in terms of photon polarization correlations. His conclusions are in agreement with ours and provide a simple example showing why nonlocal hidden-variable theories are unappealing. We extend his arguments in order to emphasize that spin-\textonehalf{} physics is in some ways closer to classical intuition than that based on "few photon" physics.

John Stewart Bell

Federico Laudisa

The Bell 1964 theorem states that nonlocality is a necessary feature of hidden variable theories that reproduce the statistical predictions of quantum mechanics. In view of the no-go theorems for non-contextual hidden variable theories already existing up to 1964, and due to Gleason and Bell, one is forced to acknowledge the contextual character of the hidden variable theory which the Bell 1964 theorem refers to. Both the mathematical and the physical justifications of this contextualism are reconsidered. Consequently, the role of contextualism in recent no-hidden-variables proofs and the import of these proofs are investigated. With reference to the physical intuition underlying contextualism, the possibility is considered whether a context-dependence of individual measurement results is compatible with context-independence of the statistics of measurement results.