HILBERT SPACE QUANTUM MECHANICS IS CONTEXTUAL (REPLY TO R. B. GRIFFITHS)

In a recent paper, Robert Griffiths has argued, based on the consistenthistories interpretation, that Hilbert space quantum mechanics (QM) is non-contextual.According to Griffiths, the problem of contextuality disappears if the apparatus is“designed and operated by a competent experimentalist” and we accept the SingleFramework Rule (SFR). In the present paper we will argue that Griffiths’ conclusion isuntenable. Firstly, we will argue that Kochen-Specker (KS) type contextuality hasnothing to do with the measurement processes nor the measurement problem – solvingthis problem does not necessarily remove contextuality. Secondly, that theconsideration of counterfactual situations is endemic when reasoning by means ofphysics. Griffiths’ SFR amounts to an unprincipled (or impractical) denial of this fact.Thirdly, that Griffiths’ demonstration implies, as a direct consequence, that QM allowsa Global Valuation for all properties independently of the context. This would mean notonly that KS theorem is false, but also that the SFR is completely unnecessary. Finally,we will argue that quantum contextuality should be reconsidered – instead of as aproblem that we need to escape – as a main feature of the formalism which must bepositively taken into account in order to provide a coherent representation of physicalreality and explain what QM is talking about.