Decoherence,Locality and Causation Without Determinism

Federico Laudisa

Paolo Faglia

Using a 'reformulation of Bell's theorem', Waegell and McQueen, (2020) argue that any local theory which does not involve retro-causation or fine-tuning must be a many-worlds theory. Moreover they argue that non-separable many-worlds theories whose ontology is given by the wavefunction involve superluminal causation, as opposed to separable many-worlds theories (e.g. Waegell, 2021; Deutsch and Hayden 2000). I put forward three claims. (A) I challenge their argument for relying on a non-trivial, unquestioned assumption about elements of reality which allows Healey's approach (Healey, 2017b) to evade their claim. In an attempt to respond to (A), Waegell and McQueen may restrict their claim to theories which satisfy such an assumption, however, I also argue that (B) their argument fails to prove even the so weakened claim, as exemplified by theories that are both non-separable and local. Finally, (C) by arguing for the locality of the decoherence-based Everettian approach (Wallace, 2012) I refute Waegell and McQueen's claim that wavefunction-based ontologies, and more generally non-separable ontologies, involve superluminal causation. I close with some doubtful remarks about separable Everettian interpretations as compared to non-separable ones.

H. Pierre Noyes

Richard Healey

Quantum theory launched a revolution in twentieth-century physics. But we have yet to appreciate the revolution’s significance for philosophy. Most studies of the conceptual foundations of quantum theory first try to interpret the theory—to say how the world could possibly be the way the theory says it is. But, though fundamental, quantum theory is enormously successful without describing the world in its own terms. When properly applied, models of quantum theory offer good advice on the significance and credibility of claims about the world expressed in other terms. This first of several philosophical lessons of the quantum revolution dissolves the quantum measurement problem. Pragmatist treatments of probability and causation show how quantum theory may be used to explain the non-localized correlations that have been thought to involve ‘spooky’ instantaneous action at a distance. Given environmental decoherence, a pragmatist inferentialist approach to content shows when talk of quantum probabilities is licensed, resolves any residual worries about whether a quantum measurement has a determinate outcome, and solves a dilemma about the ontology of a quantum field theory. This approach to meaning and reference also reveals the nature and limits of objective description in the light of quantum theory. While these pragmatist approaches to probability, causation, explanation, and content may be independently motivated by philosophical argument, their successful application here illustrates their practical importance in helping philosophers come to terms with the quantum revolution.

Peter Ryser

Abstract: In this paper a new interactionistic model of mental causa-tion is developed. By analysing the results of physics and neurosci-ence it is shown that the macroscopic cerebral activity and the resulting behavioural output is not strictly determined. This opens up the possibility that a non-physical mind can influence which of the physically allowed brain states is realised. Most models of mental causation postulate that there are coherent quantum states in the brain which could be influenced by a local mind-brain interaction. Due to environmental decoherence, however, it is questionable whether coherent quantum states can exist in the warm and wet brain. The here presented ‘creative choice theory’solves the problem of envi-ronmental decoherence by including the environment. The whole uni-verse is considered as a quantum system that is in superposition of alternative realities. It is then assumed that a universal mind col-lapses the universal wave-function whilst individual minds (as part of the universal mind) interact with individual brains. This leads to a holistic model of reality that could also provide an explanation for ESP-phenomena and mystical experiences. 1.

Claude Amra, Michel Lequime, Myriam Zerrad