"The Kochen-Specker (KS) theorem demonstrates that it is, in general, impossible to ascribe to an individual quantum system a definite value for each of a set of observables not all of which necessarily commute. Of course elementary quantum metaphysics insists that we cannot assign definite values to noncommuting observables; the point of the KS theorem is to extract this directly from the quantum-mechanical formalism, rather than merely appealing to precepts enunciated by the founders..."

David Mermin [Mermin, 1990b]

Michael Kernaghan has some pages about Kochen-Specker.

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EPR Bell's theorem Kochen and Specker GHZ Mermin

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