2018 Annual Lecture in Memory of Prof. Itamar Pitowsky

The meaning and status of contextuality and relationality in quantum mechanics

Mauro Dorato, Department of Philosophy, Communication and Media Studies, Università degli studi Roma Tre

Via Ostiense 234, 00146, Rome, Italy

In my paper I will evaluate two recent relationalist approaches to quantum mechanics, proposed in particular by Rovelli (1995, 1997, 2012) and Healey (2012a, 2012b, 2015, 2016, 2017a, 2017b, 2018). I will argue that both approaches are very close to a traditional interpretation to the theory (namely Bohr’s) in which very general empirical regularities revealed by measurements are used as building blocks of a “theory-of-principle-approach” to quantum mechanics in Einstein’s sense (1919). In this respect, both views are also close to Pitowsky and Bub’s “structural” understanding of quantum mechanics, regarded as a new theory of contextual probability (Pitowsky 2006) or as a new theory of information (Bub 2015).

On the one hand, by stressing a pragmatistic view of the theory and the physical situatedness of agents, Healey revives both (i) Bohr’s stress on the pragmatic role of language in understanding physical theories and (ii) his peculiar form of contextualism. In fact, it has been now historically documented that the influence of James’ thought of Bohr was very relevant (Folse 2018). Healey’s physical situatedness of agents is a basic consequence of the contextuality of the theory, proved formally by Kochen and Specker and established experimentally by the fact that quantum observations do not reveal previously possessed values of physical systems, a fact that Bohr never tired of stressing. On the other hand, Rovelli’s relational quantum mechanics (1996, 1997, 2011, 2018) is a mixture of Bohr’s and Everett’s interpretations. Like Bohr, it stresses an antirealistic understanding of the wave function. Like Everett’s relative state formulation, it insists on the perspectival nature of the quantum state of the universe.

Accordingly, both relationist interpretations of quantum theory are attempts to improve on Bohr’s too often misunderstood approach to quantum theory


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