Metaphysical Indeterminacy of Causal Relations: the Case of the Quantum Switch

Laurie Letertre (University of Munich)

19 December 2025, 16:00 (Lisbon Time – WET)

Faculdade de Letras de Lisboa

Sala Mattos Romão [C201.J] (Departamento de Filosofia)

Abstract: It is often assumed that, if c causes e, then it is determinate that c causes e. Call this principle Determinacy of Causation (DetC for short). In recent years it has been shown that DetC suffers from various objections within a Humean framework for understanding causation (Sartorio 2006, Ballarin 2014, Bernstein 2016, Swanson 2017). Our aim in this paper is to argue that recent discoveries in the foundations of quantum mechanics might give further motivations for rejecting DetC. We focus on a specific arrangement of physical operations known as quantum switch, and show that a mildly realist attitude towards this setup forces us to put DetC into question. We will then briefly discuss the possible origin of this indeterminacy, and highlight some of the consequences of abandoning DetC for theories of causation. (Joint work with Cristian Mariani.)