French on London and Bauer, and QBism

TL;DR

This paper analyzes two phenomenology-inspired interpretations of quantum mechanics, the London-Bauer-French (LBF) interpretation and QBism. It critically evaluates three areas of tension—introspection, the nature of the measurement apparatus, and intersubjectivity—to determine where QBism aligns or clashes with phenomenology. The author argues that QBism can be reconciled with Zahavi's correlationism and Husserlian intersubjectivity, challenging French's claim of deep incompatibility, while also explaining why QBism remains at odds with LBF's conception of measurement and Merleau-Ponty's reading. It further contends that the prolongation of sensing apparatus, though contested, can be defended from a metrology perspective and that QBism offers a robust account of intersubjective agreement in light of extended Wigner's friend theorems. The work reframes how phenomenology informs QBism and suggests paths for integrating these viewpoints in QM foundations.

Abstract

In this article I compare two interpretations of quantum mechanics (QM) that draw inspiration from phenomenology: the London-Bauer-French interpretation (hereafter LBF) as articulated by Steven French, and QBism. I give special attention to certain disagreements between QBism and LBF identified French's work, as well as French's related claims that QBism may be at odds with key ideas in phenomenology. My main finding is that QBism does not fare so badly with phenomenology as French makes out; in particular it can be made compatible with Zahavi's correlationism and Husserl's notion of intersubjectivity, both of which strongly inform LBF. Nevertheless, I concur with French's argument that QBism is incompatible with the conception of quantum measurement in LBF, hence also with that of Merleau-Ponty, as the latter based his own analysis on that of London and Bauer. I explain why I find QBism's account preferable in this case.