What Does '(Non)-Absoluteness of Observed Events' Mean?

TL;DR

This paper critically examines recent theorems on the non-absoluteness of observed events in quantum mechanics, arguing they do not necessarily imply radical metaphysical non-absoluteness and exploring alternative relational interpretations.

Contribution

It clarifies the implications of key theorems on quantum non-absoluteness and proposes a novel relational approach with relativized states and absolute events.

Findings

Theorems demonstrate world disaccord if quantum mechanics is universal, but not necessarily metaphysically radical.

Ormrod and Barrett's theorem supports Everettian interpretations or non-universality of quantum mechanics.

A relational approach with relativized states and absolute observed events is a promising alternative.

Abstract

Recently there have emerged an assortment of theorems relating to the 'absoluteness of emerged events,' and these results have sometimes been used to argue that quantum mechanics may involve some kind of metaphysically radical non-absoluteness, such as relationalism or perspectivalism. However, in our view a close examination of these theorems fails to convincingly support such possibilities. In this paper we argue that the Wigner's friend paradox, the theorem of Bong et al and the theorem of Lawrence et al are all best understood as demonstrating that if quantum mechanics is universal, and if certain auxiliary assumptions hold, then the world inevitably includes various forms of 'disaccord,' but this need not be interpreted in a metaphysically radical way; meanwhile, the theorem of Ormrod and Barrett is best understood either as an argument for an interpretation allowing multiple outcomes per observer, such as the Everett approach, or as a proof that quantum mechanics cannot be universal in the sense relevant for this theorem. We also argue that these theorems taken together suggest interesting possibilities for a different kind of relational approach in which dynamical states are relativized whilst observed events are absolute, and we show that although something like 'retrocausality' might be needed to make such an approach work, this would be a very special kind of retrocausality which would evade a number of common objections against retrocausality. We conclude that the non-absoluteness theorems may have a significant role to play in helping converge towards an acceptable solution to the measurement problem.