Aurélien Drezet has attempted in Found. Phys. 54(1), 5 (2023) to defend Relational Quantum Mechanics (RQM) against our recent critique, entitled Relational Quantum Mechanics is incompatible with quantum mechanics, published in Quantum 7, 1015 (2023). Drezet not only misrepresents our work, but he also misconstructs the very theory (RQM) that he claims to defend.

It is shown here that Suarez (Found. Phys. 38:583, 2008) wrongly presents the assumptions behind the Leggett’s inequalities, and their modified form used by Groeblacher et al. (Nature 446:871, 2007) for an experimental falsification of a certain class of non-local hidden variable models.

All separable states satisfy all Bell-type inequalities, which involve as their assumption only existence of local realistic (local hidden variable) models of the correlations of spatially separated systems, observed by two or more observers making independent decisions on what to measure (free will). The recent observation by Loubenets, that some separable states do not satisfy the original Bell inequality (1964) has no consequences whatsoever for the studies of the relation of separability with local realism. The original Bell inequality was derived (...) using an additional assumption that the local results for a certain pair of local settings reveal perfect Einstein–Podolsky–Rosen (EPR) correlations. Therefore violation of this inequality by some quantum predictions implies that either (i) the predictions do not allow a local realistic model, or (ii) the predictions do not have the required EPR correlations, or finally both (i) and (ii). (shrink)

We showed in a recent article (Lawrence et al. 2023. Quantum, 7, 1015), that relative facts (outcomes), a central concept in Relational Quantum Mechanics, are inconsistent with Quantum Mechanics. We proved this by constructing a Wigner-Friend type sequential measurement scenario on a Greenberger-Horne-Zeilinger (GHZ) state of three qubits, and making the following assumption: “if an interpretation of quantum theory introduces some conceptualization of outcomes of a measurement, then probabilities of these outcomes must follow the quantum predictions as given by the (...) Born rule.” Our work has been criticized by Cavalcanti et al. (2023. European Journal for Philosophy of Science, 13(4),55). In this note we show that their critique, based on their own reformulation of our argument, does not apply to our paper. It also raises questions of principle which are not answered within the framework of Relational Quantum Mechanics. (shrink)