Observer-Equivariant Ontology (v1) develops a compact ontological and methodological stance tailored to modern physics: the fundamental objects are not “systems in themselves” but observer perspectives related by symmetry. The paper formulates this as an equivalence requirement across admissible perspectives and uses it to motivate why the epistemic core of physics is structurally invariant content (relations, constraints, symmetries), rather than observer-dependent representations. The text is written as a conceptual companion to the more technical parts of the series. It clarifies: (i) what is being quantified over when physics speaks about “observers” or “frames”, (ii) how invariance and gauge redundancy enter as structural constraints on admissible descriptions, and (iii) how a perspective-based ontology can be stated without committing to instrumentalism. Where needed, the paper points to the technical manuscripts for constructions such as symmetry-constrained measures and history groupoids. This upload is version v1 of the paper. Version DOI (this record): 10.5281/zenodo.17929468 Series DOI (all versions): 10.5281/zenodo.17929467
Observer-Equivariant Ontology (v1) develops a compact ontological and methodological stance tailored to modern physics: the fundamental objects are not “systems in themselves” but observer perspectives related by symmetry. The paper formulates this as an equivalence requirement across admissible perspectives and uses it to motivate why the epistemic core of physics is structurally invariant content (relations, constraints, symmetries), rather than observer-dependent representations. The text is written as a conceptual companion to the more technical parts of the series. It clarifies: (i) what is being quantified over when physics speaks about “observers” or “frames”, (ii) how invariance and gauge redundancy enter as structural constraints on admissible descriptions, and (iii) how a perspective-based ontology can be stated without committing to instrumentalism. Where needed, the paper points to the technical manuscripts for constructions such as symmetry-constrained measures and history groupoids. This upload is version v1 of the paper. Version DOI (this record): 10.5281/zenodo.17929468 Series DOI (all versions): 10.5281/zenodo.17929467
Observer Equivariance (OE) is proposed as an interpretation of quantum theory based on a single structural principle: objectivity is invariance under changes of observer perspective. The framework is formulated using a projection p:\mathcal O \to \mathcal S, where \mathcal O is a groupoid of observer perspectives (descriptions) and \mathcal Srepresents structural content intended to be objective. Within this setting, the paper links three familiar pillars of quantum theory as consequences of one invariance requirement: Symmetry. Physical symmetries are characterized as automorphisms of \mathcal S that are liftable to \mathcal O in a way compatible with the relevant gauge freedom. This recovers Wigner/Uhlhorn-type constraints from a general “liftability” viewpoint. Born weights. Event weights are constrained by invariance under a minimal internal “mixing” operation (unitary change of basis within a fixed structural event), together with coarse graining and phase invariance. A proof sketch shows how this yields a functional equation that forces quadratic (Born-type) weights. Uncertainty. Translational perspective changes motivate a Fourier/Pontryagin-duality analysis in which Plancherel/Parseval norm preservation selects an L^2 structure and yields standard Fourier uncertainty relations as representation-theoretic constraints. The article positions OE relative to QBism and Relational Quantum Mechanics: it shares the view that “facts” and state assignments are perspective-indexed, while differing in that symmetry constraints and the probability calculus are treated as structural necessities derived from invariance, rather than as purely epistemic or decision-theoretic postulates. DOI (this version): 10.5281/zenodo.18221625 Concept DOI (all versions): 10.5281/zenodo.18221624 AI use: AI systems (ChatGPT, Gemini, Grok, and Claude) were used for drafting assistance, language editing, and mathematical polishing. The author reviewed the manuscript and takes full responsibility for all claims and any errors.
This working paper develops the structural consequences of the observer-equivariance framework for the space of possible histories in quantum theory and field theory. The observer-equivariance programme treats observer perspectives as the primary objects and derives physical law from the requirement that descriptions related by a symmetry group Gmust be mutually coherent. A technical companion paper shows that this principle uniquely determines (up to phase) a G-equivariant path-integral distribution on path space. Building on that result, the present paper constructs the equivariant history groupoid Hist_G. Its objects are globally consistent, anomaly-free, G-equivariant histories; its morphisms represent physical symmetries such as gauge transformations, diffeomorphisms, and global symmetry actions. Together with the equivariant path-integral distribution, this yields the equivariant multiverse: a mathematically structured ensemble of admissible histories entirely determined by symmetry, observer-equivariance, and consistency conditions. The paper also analyses how standard decoherence arguments induce layers of effectively independent histories within Hist_G, providing a symmetry-controlled formulation of branching phenomena without committing to any particular interpretation of quantum mechanics. The aim is to isolate a “hard core’’ structural framework underlying multiverse-type reasoning in quantum foundations, grounded in symmetry and observer-equivariance rather than interpretational assumptions.
This paper argues that observer equivariance is best understood not merely as an interpretive motif attached to particular physical theories, but as a higher-order constraint on the admissible form of physical theory. If physical law is to count as genuinely public, it must be transportable across admissible changes of perspective without loss of objective content. On this view, observer equivariance constrains not only the covariance of equations, but also the admissibility of representational frameworks, the structure of weighting schemes, the role of compatibility conditions, and the interpretation of residual freedom in theory construction. The argument is synthetic, drawing together earlier work on shared physical law, translational and spectral form, path-integral measure selection, Born-type weighting, and Machian boundary constraints. Three levels of claim are kept distinct throughout: conceptual claims about the public form of physics, partial formal results (such as orbitwise rigidity of weighting schemes and conditional uniqueness of quadratic weighting under additional structural assumptions), and conjectural extensions (most notably to renormalization-related residual freedom). The main philosophical consequence is a strengthened, prospective motivation for epistemic structural realism: the structural content of physics is not merely what happens to survive theory change, but what must already be stably coordinable across admissible perspectives if public physical knowledge is to be possible at all. This route is contrasted with Worrall's retrospective appeal to theory change, with Ladyman and French's ontic structural realism, and with Rovelli's relational quantum mechanics. Keywords: observer equivariance, epistemic structural realism, philosophy of physics, symmetry and invariance, intersubjectivity, path-integral measure, Born rule, Machian inertia, renormalization.
This paper argues that, where deterministic and indeterministic formulations agree on empirically corroborated structure while differing in their completion of structure that remains empirically underdetermined, features invariant across these formulations warrant ontological commitment, whereas any warrant attaching to features that vary across them is categorically more provisional. Because deterministic and indeterministic completions are always formally available, while additional grounds for preferring particular completions are contingent and defeasible, empirically corroborated structure alone cannot determine whether reality is fundamentally deterministic or indeterministic, or whether that very distinction belongs only to specific representations of it.
On this basis, I advance a model-invariance criterion according to which structural features are candidates for realist commitment insofar as they are empirically corroborated within a regime and preserved across the admissible formulations of that structure. I show how such invariant content can be characterised in mathematically intelligible ways, yielding a fallibilist form of structural realism grounded in model-invariance rather than in the specific form of any given mathematical representation. Features such as conservation relations, invariant measures, symmetries, and probability or correlation structures over observable histories may satisfy this criterion. By contrast, the localisation of modal selection---whether in fine-grained initial conditions, stochastic outcomes, or state-update and collapse mechanisms---may vary across empirically admissible formulations and therefore constitute a gauge-like representational freedom.
This framework offers a realist ontology for modern physics that combines empirical openness with resistance to metaphysical overreach.
This article develops a structural interpretation of “archetype” within a framework where observer equivalence—understood as invariance under admissible perspective change—serves as the criterion of objectivity. Drawing on relativity theory, gauge structure, and quantum measurement theory, archetypes are reconstructed not as psychological images but as form-generating invariants that enable translatability and re-identifiability across perspectives. The paper argues that actuality should be understood as the outcome of selection and symmetry breaking rather than as the manifestation of pre-given substance. Within this framework, consciousness is interpreted structurally as perspective-bound actualization: the functional locus at which a possibility structure becomes bound to determinate outcomes, without invoking a homunculus and without endorsing “consciousness causes collapse” interpretations. The aim is to clarify the ontological implications of modern physics under a perspectival but non-subjectivist conception of physical law. The text is intentionally compact and programmatic, serving as a position note within a broader research agenda on observer equivalence and structural ontology.
This paper interprets Haag’s theorem as more than a technical obstruction to the interaction picture in relativistic quantum field theory. It argues that the theorem reveals a deeper structural limitation of global representation-based ontology: an interacting QFT cannot, under the assumptions of the theorem, be understood as a simple unitary deformation of a free theory within one fixed Fock representation. The paper connects this lesson to algebraic quantum field theory, superselection sectors, locally covariant QFT, Wilsonian renormalization, and effective field theory. It proposes that these developments all point toward a common principle: physical objectivity is not grounded in a privileged representation, but in structural content preserved under admissible transformations between perspectives, representations, sectors, scales, or regions. The paper does not claim to solve Haag’s theorem or construct interacting QFTs. Its aim is interpretive: to show how Haag’s theorem is naturally intelligible within the observer-equivariant framework, where objectivity is understood as invariant or equivariant structure rather than as a view from one absolute representation.