QBism’s Primitive, Participatory Experience: Quantum Agency and the First-Person World

QBism (Quantum Bayesianism), developed principally by Christopher A. Fuchs and Rüdiger Schack, is not itself a theory of consciousness, but its interpretation of quantum mechanics has unusually strong implications for phenomenal consciousness because experience is already primitive in its formulation and it places the individual agent’s personal experience at the conceptual foundation of quantum theory. To be explicit: Qbism is an interpretation of quantum mechanics with implications for consciousness, rather than a quantum-neural mechanism that generates consciousness.

Qbism’s Quantum State

In Qbism, a quantum state is not an objective property of a system but an agent’s personal probability assignment concerning the possible consequences of actions upon an external world; measurement is such an action, and its outcome is a new experience occurring for that agent (Fuchs and Schack, 2013, 2015; Fuchs, Mermin, and Schack, 2014; Fuchs and Stacey, 2025). If developed into a theory of phenomenal consciousness, QBism would therefore suggest that first-person experience cannot be eliminated from the ontology or reconstructed solely from a detached third-person description—but this inference must be carefully qualified, because QBism presently presupposes agents and experiences rather than explaining why some physical systems possess phenomenal consciousness.

In other words, QBism holds that a quantum state is not a property of a physical system but a personal degree of belief held by an agent about the outcomes of her own future actions, that the Born rule is an empirically motivated norm of rationality rather than a law of nature, and that a measurement is any action an agent takes on the world while its outcome is the experience thereby elicited (Fuchs, Mermin, and Schack, 2014). Its bearing on phenomenal consciousness is oblique but structural: experience is declared the fundamental primitive of the theory, so phenomenal states enter fundamental physics as explanans/explainers rather than explanandum/explainee, and the definiteness of measurement outcomes is grounded in the definiteness of an individual's sensory experience rather than the reverse. QBism offers no theory of consciousness and explicitly declines to give one, treating agents, actions, and experiences as terms that neither require nor admit of precise physical specification. It makes phenomenal consciousness indispensable to the foundations of physics as no other major interpretation does, while leaving every question the hard problem raises exactly where it found them.

Agent-Centered Quantum Reality

QBism begins with personalist Bayesian probability. Probabilities—including quantum probabilities—are an individual agent’s degrees of belief concerning possible future experiences, not objective propensities residing in physical systems. Consequently, the wavefunction or density operator does not describe an objectively existing physical condition. Even a probability-one assignment expresses maximal personal certainty rather than an element of reality guaranteed to exist before measurement (Fuchs and Schack, 2013; Fuchs, 2023; Fuchs and Stacey, 2025).

This does not make quantum theory arbitrary subjectivism. Ordinary Bayesian coherence constrains an agent’s probabilities, while the Born rule adds a specifically quantum normative constraint connecting probabilities for alternative possible actions. In the QBist program, especially when quantum states are represented through symmetric informationally complete measurements (SICs), the Born rule can be understood as an empirically discovered modification of classical probability coherence—a rule telling an agent how different expectations should hang together when dealing with a quantum world (Fuchs and Schack, 2009, 2013; DeBrota et al., 2021).

Redefining Measurement

Most important for consciousness, QBism redefines measurement. Measurement is not a passive reading of an already possessed property; it is an action an agent takes upon something external to herself. The measurement outcome is the particular experience generated for that agent through the interaction (Fuchs, Mermin, and Schack, 2014). Thus the conceptual sequence is:

agent → action upon world → unpredictable consequence → personal experience → revised expectations.

Wavefunction “collapse” accordingly requires no causal intervention by consciousness. What changes is the agent’s quantum-state assignment after experience. QBism therefore differs fundamentally from von Neumann-Wigner-type consciousness-collapse interpretations.

Phenomenal Consciousness as First-Person Primitive

Translated into consciousness theory, QBism’s most striking implication is the irreducibility of the first-person standpoint. Quantum theory is explicitly “single-user”: each agent deploys the formalism to organize her expectations for her own possible experiences (Fuchs, 2023). Different agents can legitimately possess different state assignments because the quantum state represents neither an observer-independent physical object nor a universal God’s-eye description.

Phenomenal consciousness has an analogous perspectival structure. My pain, redness, warmth, or auditory experience occurs for me in a way that another observer’s third-person description does not reproduce. QBism does not prove that phenomenal consciousness is ontologically irreducible, but its architecture undermines any assumption that physics must fundamentally consist of an exhaustive observer-independent description from which the first-person perspective should simply disappear. This is an inference from QBism, not an explicit QBist solution to the hard problem.

Indeed, Fuchs and Schack go further than mere epistemic subjectivism. They describe the outcome of a quantum interaction as a genuinely new experience, not the revelation of an antecedently possessed value, and have suggested “experience” itself as a possible candidate for the fundamental material of reality (Fuchs and Schack, 2014). Fuchs connects this proposal with William James’s “pure experience” and John Wheeler’s observer-participancy, while emphasizing that QBism has not yet completed the ontology required to make this proposal precise (Fuchs, 2016).

This opens a potentially radical consciousness interpretation. Phenomenal experience might not be something that must somehow be manufactured from a wholly experience-free reality; experience-like events could belong to the fundamental transactional structure of reality itself. But Fuchs explicitly recognizes the need to “deanthropocentrize” this notion—to distinguish elementary “pure experience” from the sophisticated agents who experience and reason about quantum outcomes. QBism therefore gestures toward panexperientialism or Jamesian neutral monism without presently committing itself to either.

Participatory Reality, Novelty, and Conscious Experience

QBism calls its emerging metaphysics participatory realism. It rejects both naive realism, in which quantum theory mirrors a completely pre-existing world, and idealism, in which reality is merely constructed by mind. There is a real external world that resists the agent and produces consequences the agent cannot dictate. Yet reality is not fully specified independently of interactions: an agent acts upon the world, and something genuinely new arises in response (Fuchs, 2016; DeBrota, Fuchs, and Schack, 2024).

Phenomenal consciousness would fit naturally into this participatory structure. Experience would not be a detached internal picture representing an already complete external reality. It would be an event arising at the active interface between an embodied agent and a world possessing its own capacities for novelty. This interpretation has prompted Fuchs to engage increasingly with phenomenology, especially Merleau-Ponty, because both approaches reject an absolute separation between an observing subject and an independently completed object-world (Fuchs, 2023).

Wigner’s-friend scenarios sharpen the point. One agent’s outcome is her personal experience; another agent outside the laboratory need not assign that outcome an observer-independent quantum fact before interacting with the first agent. QBism therefore takes perspectival experience seriously without denying an external world or the possibility of intersubjective agreement (Fuchs, 2023; Schack, 2023). Reality is neither purely private nor simply a view from nowhere.

What QBism Does—and Does Not—Explain About Consciousness

QBism’s potential contribution to consciousness is consequently profound but sharply limited. It implies that physics need not begin from exclusively third-person entities and subsequently face the seemingly impossible task of explaining subjectivity. Agents, actions, consequences, and experiences are conceptually prior to the quantum state. Phenomenal experience therefore cannot simply be dismissed as an inconvenient appearance within an allegedly complete objective wavefunction.

But QBism does not explain phenomenal consciousness, and there is only modest reason to suggest that it might. It supplies no criterion for determining which physical systems are conscious, no neural or physical mechanism generating experience, no account of phenomenal unity, and no explanation for why an experience has one qualitative character rather than another. Saying that a measurement outcome is an agent’s experience identifies where experience enters the theory; it does not explain why there is something it is like to be that agent.

This is the crucial Landscape qualification. If “agent” means a phenomenally conscious subject, QBism risks taking the explanandum as a primitive: consciousness helps define what a quantum measurement outcome is, but quantum theory then cannot independently explain consciousness. If, alternatively, QBism’s eventual ontology generalizes “experience” into elementary participatory events throughout nature, it would require an additional theory explaining how such primitive events become unified human phenomenal consciousness—the familiar combination or constitution/decombination problem of panpsychism and idealism, respectively.

Fuchs is explicit that QBism remains a research program seeking its deeper ontology (Fuchs, 2023; Fuchs and Stacey, 2025). Its significance for consciousness is therefore not that quantum Bayesian probabilities generate qualia. Rather, QBism radically reframes the explanatory setting: experience may belong among the primitives from which our conception of physical reality begins, rather than being an anomalous late product that physics must somehow derive after constructing a world without subjects. Thus, QBism elevates personal experience from something physics describes from outside to something quantum theory presupposes from inside, while leaving open whether its eventual participatory ontology will explain phenomenal consciousness or merely give consciousness a fundamentally different metaphysical setting.

References

DeBrota, J. B., Fuchs, C. A., Pienaar, J. L., and Stacey, B. C. (2021). Born’s rule as a quantum extension of Bayesian coherence. Physical Review A, 104, 022207.

DeBrota, J. B., Fuchs, C. A., and Schack, R. (2024). Quantum dynamics happens only on paper: QBism’s account of decoherence. Physical Review A, 109, 062216.

Fuchs, C. A. (2010). QBism, the perimeter of Quantum Bayesianism. arXiv:1003.5209.

Fuchs, C. A. (2016). On participatory realism. In I. T. Durham and D. Rickles (Eds.), Information and Interaction: Eddington, Wheeler, and the Limits of Knowledge. Springer.

Fuchs, C. A. (2023). QBism, where next? In P. Berghofer and H. A. Wiltsche (Eds.), Phenomenological Approaches to Quantum Mechanics. Routledge.

Fuchs, C. A., Mermin, N. D., and Schack, R. (2014). An introduction to QBism with an application to the locality of quantum mechanics. American Journal of Physics, 82(8), 749–754.

Fuchs, C. A., and Schack, R. (2009). A quantum-Bayesian route to quantum-state space. Foundations of Physics, 41, 345–356.

Fuchs, C. A., and Schack, R. (2013). Quantum-Bayesian coherence. Reviews of Modern Physics, 85, 1693–1715.

Fuchs, C. A., and Schack, R. (2014). Quantum measurement and the Paulian idea. In H. Atmanspacher and C. A. Fuchs (Eds.), The Pauli-Jung Conjecture and Its Impact Today. Imprint Academic.

Fuchs, C. A., and Schack, R. (2015). QBism and the Greeks: Why a quantum state does not represent an element of physical reality. Physica Scripta, 90, 015104.

Fuchs, C. A., and Stacey, B. C. (2025). QBism, polishing some points. arXiv:2512.14122.

Schack, R. (2023). When will two agents agree on a quantum measurement outcome? Intersubjective agreement in QBism. arXiv:2312.07728.

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