Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Routledge eBooks

Putting Some Flesh on the Participant in Participatory Realism

Steven French

Published Nov 20, 2023• 4 citations
Publisher

Abstract

The history of QBism is interestingly complex, leading to misunderstandings and misapprehensions as to its core features. Fuchs has usefully situated those features within the framework constituted by forms of ‘participatory realism’ according to which measurement devices should be considered to be extensions of agents. Examining that claim, Pienaar has articulated the conditions that such devices must meet to be so considered. However, there has yet been little similar consideration of the conditions that agents must meet in this regard. Here I shall examine the proposal that adopting a phenomenological stance may fill the gap in the QBists’ picture and I shall present an alternative ‘correlational’ account.

DOI
10.4324/9781003259008-12

Related papers

The Limit and Its Ground. QBism, Scientific Realism, and the Born Rule

Harald A Wiltsche

QBists insist that theirs is a realist position while denying that the quantum formalism represents a mind-independent world. The insistence is hard to place. The realism debate is throughout a dispute about represented content, so a theory that denies standing in the representation relation appears not to take up a position within that debate at all. This paper examines the most developed attempt to make good on the QBist claim--David Glick's perspectival normative realism--and argues that it fails instructively. Glick seeks the ground of the Born rule's objectivity among states of affairs and construes an agent's perspective as a location within an already-constituted world; finding no state of affairs fit to bind every agent at once, he must book the ground as brute. Phenomenology supplies the third thing his picture lacks. A horizon is not a position within the world but the condition under which a world is given. Read as an agent's weighting--her curvature--of such a horizon, the quantum state is neither a defective description nor a brute posit, and the Born rule articulates the invariant lawfulness by which any sense confers a curvature at all.

quant-pharXiv:2609.22159•Aug 27, 2026•0 citations

QBism from a Phenomenological Point of View: Husserl and QBism

Laura de la Tremblaye

Synthese Library/Synthese library•Jan 1, 2020•23 citations

QBism: Integrating Agency and Quantum Mechanics

Hans J. Briegel, Thomas Müller

Abstract The approach to quantum mechanics that we present in this book aligns fairly well with the QBist position in quantum foundations, which takes quantum mechanics as describing the interaction of an agent with the world: A theory mainly offers a way for the agent to manage her expectations about the outcomes of her interactions, not a picture of what nature is really like. We introduce QBism briefly and situate the framework within a range of options for integrating agency and quantum mechanics. We agree with QBism on many fundamental issues, but we do not subscribe to QBism wholesale. We agree with QBism’s pragmatic outlook that takes scientific theories to be tools for agents to use, and with the QBist goal of developing a participatory realism. But we are critical of the particular idealisations that QBism in its present form subscribes to. Most importantly, we are critical of the structural choice not to resolve the agent nor the world in any detail. In our view, scientific agents learn by modelling. Models are tools that agents can use and develop in dealing with the world. Guided by concrete examples, we describe a scientific modelling framework that allows for loops of three different degrees of difficulty and complexity. These range from quantum state updating, which neatly fits the QBist approach of working within a fixed probability space, via a broader class of updates including so-called Hamiltonian learning, up to the most difficult cases in which true scientific creativity is at play. All three levels of difficulty need to be acknowledged for a full picture of real scientific agency. At the end of the chapter, we describe the project of modelling scientific agency itself, which leads to the topics of Chaps. 5 and 6 .

Synthese Library/Synthese library•Jan 1, 2025•0 citations

A Participatory Universe in the Realist Mode: On the Separation of Observational and Agentive Perspectives in Classical and Quantum Mechanics

Jenann Ismael

Foundations of Physics•May 2, 2025•1 citation

Mutual Recognition in the Philosophy of Physics: QBism, Phenomenology, Hegel

George Webster

Recent discussions of QBism have turned increasingly toward the question of its ontology. I argue that key insights into QBism's ontology of agency can be identified by reconstructing its response to Wigner's friend paradox. I clarify the relation between two formulations of that response: one grounded in the claim that quantum states are agents' personal probability assignments, and another grounded in the injunction to treat all users of quantum theory as agents on equal footing. Once disambiguated, these formulations reveal an implicit commitment to a mutually recognitive conception of agency, according to which the agential status of a user of quantum theory depends constitutively on the acknowledgement of other agents. This analysis clarifies what is at stake in recent QBist engagements with phenomenology - namely, the search for a more philosophically robust account of this conception of agency. I show how Merleau-Ponty's account of intersubjectivity underpins the recognitive structure implicated in QBism before tracing these themes to Hegel's account of mutual recognition. By locating QBism within a longstanding tradition of mutual recognition, I claim that we not only illuminate its theoretical structure but also open up novel conceptual resources for the rigorous articulation and justification of its ontology.

physics.hist-phCross-listedarXiv:2608.17472•Aug 19, 2026•0 citations

Substrate-Flexible Informational Quantum Mechanics: QBism, RQM, and the Question of Non-Human Epistemic Systems

Ian Staley

The QBist and Relational Quantum Mechanics (RQM) informational readings of quantum theory have long lacked a clear account of what kind of physical system qualifies as an “agent” or “observer.” Fuchs, Mermin, and Schack often treat the agent as a human physicist or Bayesian decision-maker; Rovelli suggests that any physical system may serve as a relational observer; Healey abstracts the agent into a Bayesian role without specifying its substrate; and the Khrennikov-Schack-Zwirn exchange sharpens, but does not resolve, the intersubjectivity problem. This paper argues that the QBism/RQM informational reading is best understood as substrate-flexible: any physical system whose input-output statistics exhibit quantum-probability structure, including non-trivial Contextuality-by-Default (CbD) signatures resistant to simplex-embeddable ontological models, is a candidate epistemic agent. This condition is necessary but not sufficient: agency also requires state-sensitive updating across measurement contexts. The argument preserves QBism’s rejection of view-from-nowhere objectivity while removing the assumption that agents must be human or conscious, and disciplines Rovelli’s “any physical system” claim by tying observerhood to measurable non-triviality. Engineered cortical wetware systems such as CL1 and DishBrain offer controllable, non-human, and not clearly conscious testbeds for evaluating this claim, without requiring phenomenal consciousness or quantum-coherent biological dynamics. The paper distinguishes substrate flexibility from Pienaar’s extension of the QBist agent, which expands the agent’s senses rather than its substrate; engages neo-Everettian objections; and rejects Edwards’s attempts to fold classical large language models into QBist formalism. Classical AI token-generation systems remain simplex-embeddable and therefore fail the non-triviality requirement. Substrate flexibility is thus narrower than proposals that include current AI systems.

•Aug 11, 2026•0 citations
The history of QBism is interestingly complex, leading to misunderstandings and misapprehensions as to its core features. Fuchs has usefully situated those features within the framework constituted by forms of ‘participatory realism’ according to which measurement devices should be considered to be extensions of agents. Examining that claim, Pienaar has articulated the conditions that such devices must meet to be so considered. However, there has yet been little similar consideration of the conditions that agents must meet in this regard. Here I shall examine the proposal that adopting a phenomenological stance may fill the gap in the QBists’ picture and I shall present an alternative ‘correlational’ account.
QBists insist that theirs is a realist position while denying that the quantum formalism represents a mind-independent world. The insistence is hard to place. The realism debate is throughout a dispute about represented content, so a theory that denies standing in the representation relation appears not to take up a position within that debate at all. This paper examines the most developed attempt to make good on the QBist claim--David Glick's perspectival normative realism--and argues that it fails instructively. Glick seeks the ground of the Born rule's objectivity among states of affairs and construes an agent's perspective as a location within an already-constituted world; finding no state of affairs fit to bind every agent at once, he must book the ground as brute. Phenomenology supplies the third thing his picture lacks. A horizon is not a position within the world but the condition under which a world is given. Read as an agent's weighting--her curvature--of such a horizon, the quantum state is neither a defective description nor a brute posit, and the Born rule articulates the invariant lawfulness by which any sense confers a curvature at all.
Abstract The approach to quantum mechanics that we present in this book aligns fairly well with the QBist position in quantum foundations, which takes quantum mechanics as describing the interaction of an agent with the world: A theory mainly offers a way for the agent to manage her expectations about the outcomes of her interactions, not a picture of what nature is really like. We introduce QBism briefly and situate the framework within a range of options for integrating agency and quantum mechanics. We agree with QBism on many fundamental issues, but we do not subscribe to QBism wholesale. We agree with QBism’s pragmatic outlook that takes scientific theories to be tools for agents to use, and with the QBist goal of developing a participatory realism. But we are critical of the particular idealisations that QBism in its present form subscribes to. Most importantly, we are critical of the structural choice not to resolve the agent nor the world in any detail. In our view, scientific agents learn by modelling. Models are tools that agents can use and develop in dealing with the world. Guided by concrete examples, we describe a scientific modelling framework that allows for loops of three different degrees of difficulty and complexity. These range from quantum state updating, which neatly fits the QBist approach of working within a fixed probability space, via a broader class of updates including so-called Hamiltonian learning, up to the most difficult cases in which true scientific creativity is at play. All three levels of difficulty need to be acknowledged for a full picture of real scientific agency. At the end of the chapter, we describe the project of modelling scientific agency itself, which leads to the topics of Chaps. 5 and 6 .
Recent discussions of QBism have turned increasingly toward the question of its ontology. I argue that key insights into QBism's ontology of agency can be identified by reconstructing its response to Wigner's friend paradox. I clarify the relation between two formulations of that response: one grounded in the claim that quantum states are agents' personal probability assignments, and another grounded in the injunction to treat all users of quantum theory as agents on equal footing. Once disambiguated, these formulations reveal an implicit commitment to a mutually recognitive conception of agency, according to which the agential status of a user of quantum theory depends constitutively on the acknowledgement of other agents. This analysis clarifies what is at stake in recent QBist engagements with phenomenology - namely, the search for a more philosophically robust account of this conception of agency. I show how Merleau-Ponty's account of intersubjectivity underpins the recognitive structure implicated in QBism before tracing these themes to Hegel's account of mutual recognition. By locating QBism within a longstanding tradition of mutual recognition, I claim that we not only illuminate its theoretical structure but also open up novel conceptual resources for the rigorous articulation and justification of its ontology.
The QBist and Relational Quantum Mechanics (RQM) informational readings of quantum theory have long lacked a clear account of what kind of physical system qualifies as an “agent” or “observer.” Fuchs, Mermin, and Schack often treat the agent as a human physicist or Bayesian decision-maker; Rovelli suggests that any physical system may serve as a relational observer; Healey abstracts the agent into a Bayesian role without specifying its substrate; and the Khrennikov-Schack-Zwirn exchange sharpens, but does not resolve, the intersubjectivity problem. This paper argues that the QBism/RQM informational reading is best understood as substrate-flexible: any physical system whose input-output statistics exhibit quantum-probability structure, including non-trivial Contextuality-by-Default (CbD) signatures resistant to simplex-embeddable ontological models, is a candidate epistemic agent. This condition is necessary but not sufficient: agency also requires state-sensitive updating across measurement contexts. The argument preserves QBism’s rejection of view-from-nowhere objectivity while removing the assumption that agents must be human or conscious, and disciplines Rovelli’s “any physical system” claim by tying observerhood to measurable non-triviality. Engineered cortical wetware systems such as CL1 and DishBrain offer controllable, non-human, and not clearly conscious testbeds for evaluating this claim, without requiring phenomenal consciousness or quantum-coherent biological dynamics. The paper distinguishes substrate flexibility from Pienaar’s extension of the QBist agent, which expands the agent’s senses rather than its substrate; engages neo-Everettian objections; and rejects Edwards’s attempts to fold classical large language models into QBist formalism. Classical AI token-generation systems remain simplex-embeddable and therefore fail the non-triviality requirement. Substrate flexibility is thus narrower than proposals that include current AI systems.