An influential tradition in the foundations and philosophy of quantum theory (QT) claims that if we reject supplementing QT with hidden variables and consider that unitary QT is correct and, in principle, universal, we should adopt a relationalist approach to QT. This tradition involves a series of approaches that relativize measurement outcomes to, for example, worlds, systems, agents, or reference frames. It includes Everett’s Relative-State formulation of QT, the Many-worlds Interpretation, Relational Quantum Mechanics, QBism, Healey’s Pragmatism, and Diek’s perspectival modal interpretation. These approaches have potential costs connected with their relationalism that may make them unattractive. Thus, if there is a non-relationalist non-hidden variable universal approach to QT, it should be taken seriously. I will present an approach of this kind called Endeterminacy-Based Quantum Theory (EBQT). EBQT circumvents relationalism by constructing an account of determinate and indeterminate properties that is neither relational nor perspectival while maintaining unitary non-hidden variable universal QT. In situations where a relationalist is pressed to assume that measurement outcomes are relativized, such as in the extended Wigner’s friend scenarios, for EBQT there are no determinate outcomes but systems with certain non-relational indeterminate properties. In this approach, systems with determinate properties arose at some point in the past through certain interactions, and these systems further allowed other systems to have determinate properties. Systems keep having determinate properties over time because of these structured interactions represented by certain networks. In situations where there is isolation from the rest of the systems that belong to these networks, such as inside the friend’s lab in the extended Wigner’s friend scenarios, indeterminate properties absolutely arise inside the lab.
The PoP-grunch (Philosophy of Physics Graduate Lunch) is a weekly informal seminar in which graduate students in Philosophy of Physics present their work in progress. Anyone can attend. Anyone interested in presenting or being added to the mailing list should contact Dominik Ehrenfels dominik.ehrenfels@wolfson.ox.ac.uk.
Philosophy of Physics Graduate Lunch Seminar Convenor: Dominik Ehrenfels
