The role of the observer remains a central conceptual challenge in the foundationsof quantum mechanics. This work examines the observer as an agent whoseparticipation is structurally indispensable for the emergence of physical facts. RelationalQuantum Mechanics and QBism—two influential agent-centered interpretations—recast quantum states, measurement outcomes, and objectivity as relationalor personalist rather than observer-independent. By analyzing their conceptualcommitments, we clarify how these frameworks illuminate the problem of subjectivityand the limits of classical realism.The discussion extends beyond physics to the broader question of whether agencyand subjectivity can be eliminated from scientific and technological practices. Drawingon insights from Pauli, Stapp, and d’Espagnat, we argue that attempts tofully operationalize the observer obscure essential features of experience and understanding.Contemporary artificial intelligence systems exemplify this tension: theydemonstrate high functional performance while lacking subjectivity, intentionality,and responsibility.We suggest that the displacement of the subject—from quantum interpretationto algorithmic decision-making—reflects a deeper structural shift in modern knowledge.Treating the observer as an agent is not merely an interpretive option but aconceptual requirement for coherent accounts of measurement, understanding, andresponsible action in an age increasingly shaped by operational intelligence withoutsubjects.
The role of the observer remains a central conceptual challenge in the foundationsof quantum mechanics. This work examines the observer as an agent whoseparticipation is structurally indispensable for the emergence of physical facts. RelationalQuantum Mechanics and QBism—two influential agent-centered interpretations—recast quantum states, measurement outcomes, and objectivity as relationalor personalist rather than observer-independent. By analyzing their conceptualcommitments, we clarify how these frameworks illuminate the problem of subjectivityand the limits of classical realism.The discussion extends beyond physics to the broader question of whether agencyand subjectivity can be eliminated from scientific and technological practices. Drawingon insights from Pauli, Stapp, and d’Espagnat, we argue that attempts tofully operationalize the observer obscure essential features of experience and understanding.Contemporary artificial intelligence systems exemplify this tension: theydemonstrate high functional performance while lacking subjectivity, intentionality,and responsibility.We suggest that the displacement of the subject—from quantum interpretationto algorithmic decision-making—reflects a deeper structural shift in modern knowledge.Treating the observer as an agent is not merely an interpretive option but aconceptual requirement for coherent accounts of measurement, understanding, andresponsible action in an age increasingly shaped by operational intelligence withoutsubjects.
This article explores the relationship between Kantian epistemology and QBism, a modern interpretation of quantum mechanics. QBism reconceives scientific objects not as independent entities but as phenomena synthesized through the observer's active role. It emphasizes the interdependence of knowledge and observation, rejecting the notion of a pre-existent, absolute reality. Much like Immanuel Kant's assertion that the thing-in-itself lies outside human cognition, QBism denies ontological status to the unobservable or unexperienced, grounding objectivity in intersubjectivity: the shared cognitive structures of human agents. Within this Critical framework, I address an objection raised by Carlo Rovelli, who critiques QBism for anchoring reality to the observer, claiming it risks falling into idealism by positioning the subject outside nature. Rovelli defends a relational view, situating the observer within the world as describable by the same physical laws that apply to all objects. In response, I argue that the QBist observer represents a universal human subject, not a single determinate agent and that intersubjective agreement ensures objectivity without collapsing into solipsism.
QBism is a recently developed version of Quantum Bayesianism. QBists think that the primitive concept of experience is the central subject of science. QBism refuses the idea that the quantum state of a system is an objective description of this system. It is a tool for assigning a subjective probability to the agent's future experience. So quantum mechanics does not directly say something about the "external world". A measurement (in the usual sense) is just a special case of what QBism calls experience and this is any action done by any agent on her external world. The result of the measurement is the experience that the agent gets from her action on her personal world. For Qbists, this way of seeing the measurement helps rejecting any non-local influences. We will examine if these claims are robust and will show that a certain number of issues needs to be clarified in order to get a coherent picture. Depending on the way these necessary clarifications are made, the global image given by Qbism can vary from pure instrumentalism to interpretations making the observer play a radical role.
Abstract This paper develops an agent-centric account of measurement that treats the preferred-basis problem as fundamentally perspectival. On this view, the system–apparatus–environment decomposition and the observables that are apt to become classically robust are determined by the physical constitution and epistemic constraints of an embodied class of agents. Decoherence then stabilises those agent-specified observables, yielding facts that are stable for us without positing an absolute, observer-independent basis. On this picture, ‘measurements’ are public not because they are metaphysically privileged, but because agents like us share the relevant sensorimotor and operational structure. I motivate this account through a discussion of two recent no-go results for relational quantum mechanics (RQM) [1, 2], and a subsequent response [3]: my aim is not to defend RQM per se, but to refine the relational insight with a principled account of basis selection rooted in embodiment. I provide a phenomenological gloss, drawing on body-schema considerations, to argue that quantum mechanics is best understood as an idiosyncratically human description of interactions with the physical world—a structurally constrained, agent-indexed framework within which classicality emerges.
Quantum mechanics reveals that physical quantities and informational states are not absolute but relational, depending on the context of interaction between systems. While classical physics already contained relational elements—most clearly in Galilean relativity and Einstein’s relational spacetime—the quantum domain extends relationality to physical properties and facts themselves. In this paper, I develop an info-computational perspective on relational quantum mechanics (RQM), conceiving observers as informational agents embedded within physical processes. Quantum states are understood as constraints on possible interactions rather than intrinsic attributes of isolated systems. I review key relational, perspectival, and information-theoretic approaches—including QBism, perspectival quantum realism, reference-frame–dependent observables, categorical quantum mechanics, and graph-based formalisms—and argue that they converge on a view of physics grounded in relations and information flow. Relational objectivity emerges through inter-agent translation rules rather than observer independence, providing a unified framework for understanding quantum measurement, inter-observer agreement, and physical ontology.
The interpretation of quantum theory known as QBism argues that many elements of the formalism have a subjective interpretation. At the same time, QBism claims to be a broadly realist programme. This implies that reality in QBism must be somehow founded upon an agent's subjective experiences (measurement outcomes). To make this idea more precise, we propose to interpret QBism's “experiences” as synonymous with the concept of “perceived phenomena” in phenomenology. This suggests an approach to ontology in which objects can only be physically real if they are in principle observable. But what does “observable” mean? Are atoms, electromagnetic fields, quantum states, or probabilities observable? Here we discuss the different answers to this question given by QBists and phenomenologists, and attempt to reconcile them.
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.