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REVIEW 4 major objections 3 minor 58 references

Relational Observables, Quiddities, and Structural Realism

T0 review · 4 major / 3 minor · reviewed 2026-08-06 · deepseek-v4-flash

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Pith's one-line read Modern spacetime physics supports modal ontic structural realism: positions, spins, and other categorical properties are internal views on a fundamentally relational modal structure.

desk verdict Adlam's internal-view proposal is new and worth engaging, but the modal reading of complete observables rests on an unforced inference from derivation order to ontology; still deserves peer review. read the letter →

arxiv 2507.20313 v1 pith:BZ76OKHF submitted 2025-07-27 physics.hist-ph

Emily Adlam This is my paper · ORCID
classification physics.hist-ph
keywords relationalobservablesmodalonticstructuralrealisminternalviewpartialandcompletediffeomorphisminvariancequantumreferenceframesquidditiesNewmanobjection
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

This paper argues that modern spacetime physics points toward a specific metaphysics: reality at bottom is modal relational structure, and what we experience as non-modal features—positions, spins, categorical properties—are 'internal views' on that structure. The argument draws on the partial/complete observables formalism and the quantum reference frame formalism, where only gauge-invariant correlations are fully real and individual quantities exist only relative to a chosen frame. In such theories one cannot write down individual trajectories first and then read correlations off them; one starts from the correlation and derives the events, so the paper reads the correlation as ontologically prior to the events. The internal-view idea is then used to show how non-modal features could emerge from purely modal structure without quiddities and without a privileged role for spacetime, and to argue that the standard Newman objection to structural realism cannot even be posed. If the paper is right, modal ontic structural realism is a viable position and laws can be understood as constraints on modal structure itself.

What carries the argument

The load-bearing mechanism is the notion of an 'internal view': choosing a subsystem of the universe (often a clock) as a reference frame, relative to which the remaining degrees of freedom take on the appearance of intrinsic, evolving properties. In the partial/complete observables formalism, complete observables are diffeomorphism-invariant correlations between partial observables; partial observables are defined on a configuration space and then constrained out of the reduced phase space, so they are extra 'unphysical' degrees of freedom that only become well-defined properties when an internal view is adopted. In the quantum reference frame formalism, the same idea appears as the perspective-neutral state $\Psi$, from which relational states $|\psi_i\rangle$ relative to clock readings $t_i$ are derived. These formalisms carry the argument because they show, in mathematical detail, relations existing without independently real relata, and because the order of derivation—from global correlation to local event—is taken as evidence that modal structure is ontologically prior to non-modal features.

What would settle it

Construct a non-trivial diffeomorphism-invariant model—say a two-variable relational toy model in the style of Rovelli's Venus/Sun example—in which the same complete observable can be derived as a summary of pre-existing actual coincidence events, without first choosing a frame and without positing the correlation function as primitive. If such a derivation can be given, the paper's inference from 'we cannot write individual trajectories' to 'correlations are ontologically prior' fails.

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Extended reading notes

Core claim

The paper's central claim is that the partial/complete observables formalism of general relativity and the quantum reference frame formalism instantiate a robust modal ontic structural realism: the physically real content of a diffeomorphism-invariant world is a holistic network of modal relations—complete observables or a perspective-neutral quantum state—while partial observables and relative states are not individually real but are aspects of that network brought into being by adopting an internal view. In the classical example of Venus and the Sun, one cannot write down the individual trajectories; one starts from the correlation $\alpha_V(\alpha_S)$, and the coincidence events are derived from it, so the correlation is ontologically prior to the actual events. In the quantum case, canonical quantization forces identities between states rather than whole histories, so manifest spatiotemporal structure cannot be retained as perspective-independent reality; only correlational structure survives. From a third-person view there is only modal structure; from an internal view—say, relative to a clock—quantum states and categorical properties appear as intrinsic features and evolve by the Schrödinger equation. The paper argues that this gives a concrete, mathematically articulated answer to how non-modal features could emerge from a purely modal reality, avoids quiddities, and blocks the Newman objection because observations cannot be separated from the structure that defines them.

Load-bearing premise

The argument's load-bearing premise is that the order in which the math lets you calculate—correlation first, individual events second—tells you which is more fundamental; if that order is only a representational convenience, the main conclusion does not follow.

Editorial extensions

If this is right

  • If the paper is right, modal ontic structural realism is a viable metaphysics for worlds governed by diffeomorphism-invariant theories: non-modal features are not fundamental but arise as internal views on modal structure.
  • The Newman objection to structural realism cannot be posed in its standard form, because observable content cannot be separated from the global modal structure that defines it, so the view does not collapse into modal empiricism.
  • Laws of nature in such worlds should be understood as constraints on modal structure itself—e.g., the Einstein equations or the Wheeler-DeWitt equation—rather than as descriptions or governors of a non-modal mosaic.
  • Position, spin, and other apparent categorical properties are not fundamental or world-independent; they exist only relative to internal views, so no quiddity is needed to individuate them and spacetime need not be given a privileged fundamental role.
  • Cross-world identity claims about partial observables must be treated carefully: a partial observable is individuated by its place in its actual relational structure, so it could not exist in a world with different modal structure.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • My inference: if the internal-view mechanism generalizes, then any theory formulated as constraints on a configuration space with gauge redundancy will exhibit apparent categorical properties that are artifacts of frame choice, so the same explanatory move could be applied outside spacetime physics.
  • My inference: the fibre-bundle and Yoneda-based generalisations the paper mentions suggest a broader moral—that relational structure can generate objects and properties whenever a 'perspective' is chosen—but this moral is not established by the paper itself.
  • My inference: if non-modal features are frame-relative views, then the distinction between modal and non-modal features is itself relative to a description level, which would dissolve some of the traditional debates the paper starts from.
  • My inference: the clock ambiguity noted in the paper is the natural stress test for this metaphysics; if different internal frames yield incompatible apparent laws, then the modal structure alone does not single out the physics we observe, and additional frame-selection principles would be needed.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

4 major / 3 minor

Summary. The paper argues that modern spacetime physics—especially diffeomorphism-invariant theories and quantum-gravity formalisms—creates serious problems for contingentist accounts of the modal/non-modal distinction, particularly those that avoid quiddities by privileging spacetime. It then proposes that the partial/complete observables formalism and the quantum reference frame (QRF) formalism support a modal ontic structural realism: complete observables are fundamentally modal relational structure, while partial observables and apparent categorical properties arise as 'internal views' on that structure. The final sections draw consequences for lawhood, arguing that the view fits constraint-based accounts and that the Newman objection to structural realism cannot be posed in its standard form.

Significance. If the central inference were secured, the paper would be a significant and original contribution: it offers a concrete, physics-grounded model for modal ontic structural realism, a response to the 'relations without relata' and manifest-image objections, and a new route around the Newman objection. The paper has real strengths: it engages specific technical formalisms (Rovelli's partial observables, Page-Wootters, perspective-neutral QRF) rather than a strawman; it is explicit about its own scope and limitations (Section 1.1 and Section 4.3); and it does not pretend the science is settled. The value is programmatic and conceptual rather than demonstrative, and the main weakness is the underdefended inference from the order of mathematical derivation to ontological priority.

major comments (4)
  1. [Section 3.1] The central inference from representational order to ontological priority is asserted rather than defended. The text moves from 'we cannot write down the individual trajectories' to the claim that the correlation expressed by αV(αS) 'is ontologically prior to the actual events.' But a complete observable such as 'the value of αV when αS = 5' is a gauge-invariant function on the reduced phase space; it can be read equally well as an actual relational fact about a particular solution, not as a modal connection. The suppressed premise is that the order in which quantities are introduced in the formalism mirrors ontological priority. Since the modal reading of complete observables and the Newman-objection response in Section 4.2 both depend on this premise, the author needs either to supply an argument for it or to weaken the claim to an interpretive proposal.
  2. [Section 3.2 and Section 4.3] The quantum case is said to give 'even stronger reasons' for a modal reading because canonical quantization identifies states rather than whole histories. But Section 4.3 concedes that the QRF/Page-Wootters program suffers from the clock ambiguity and the preferred-basis problem, and Section 3.2 notes that an interpretation of the quantum state is needed before relational statements can be connected to observations. If different clock choices produce radically different evolution laws, then the relational states and apparent categorical properties generated by taking an internal view are representation-dependent in a way that threatens the ontological conclusion. The author needs to explain why the modal reading is robust across clock choices, or to restrict the modal claim to the classical case.
  3. [Section 4.1] The claim that the connection between partial observables is metaphysically necessary is supported by the statement that 'by definition partial observables exist only as aspects of the relations encoded in complete observables.' This supports an analytic or definitional necessity within the formalism, not a metaphysical necessity. The subsequent argument that partial observables would be different if the relational structure were different is a counterpart-theoretic move that needs independent metaphysical defense. As written, the section conflates 'this formalism defines x by relation R' with 'x could not exist without R as a matter of metaphysical necessity.' Please clarify the modal status and the criteria for cross-world identity of partial observables.
  4. [Section 4.2] The paper says that adopting an internal view 'brings new kinds of properties into being,' while footnote 3 disclaims that this is a real temporal process. This is a crucial ontological claim, not a harmless turn of phrase: without an account of what makes an internal view ontologically significant rather than merely a choice of representation, the emergence of non-modal features from modal structure remains metaphorical. The manifest-image response and the Newman-objection response in this section depend on this emergence being real in some sense, so the author should specify what 'bringing into being' amounts to and why it is not just a change of description.
minor comments (3)
  1. [Throughout] There are several typos and inconsistencies: 'the the partial/complete observables' in the Introduction, 'total/partial observables' in Section 4.2, 'participatns' in the Acknowledgements, 'spacetiotemporal' and 'manifest spacetiotemporal structure' in Sections 3.2 and 4.2, and 'beteen' in Section 4.
  2. [References] Some references are incomplete: Baker (2019) lacks a venue or publication details, Ruyant (2017) lacks issue and page numbers, and Kabel et al. (2024) and Vanzella and Butterfield (2024) are cited as preprints without a publication status. Please complete these entries.
  3. [Sections 3 and 4] The terms 'internal view,' 'internal perspective,' and 'first-person perspective' are used interchangeably, but they may carry different commitments. It would help to define the intended notion and state whether the formalism requires a conscious observer or only a physical reference system.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the modal reading of complete observables is an interpretive inference from independently cited formalisms, not a definitional or fitted consequence.

full rationale

The paper's central claim is an interpretive thesis about the partial/complete observables and quantum-reference-frame formalisms, not a prediction derived from fitted parameters. The formalisms are sourced from independent literature (Rovelli 2002; Page and Wootters 1983; Vanrietvelde et al. 2020), and the modal conclusion is argued from the gauge-invariant, relational character of complete observables. The step from 'we cannot write down the individual trajectories' to the claim that the correlation is 'ontologically prior to the actual events' is a substantive philosophical inference, and therefore open to challenge, but it is not circular: the conclusion is not contained in the premise by definition, nor is it a renamed version of the formalism's output. The paper explicitly disclaims that the formalisms are conclusive evidence (Section 1.1), and it acknowledges open technical problems such as the clock ambiguity and preferred-basis problem (Section 4.3). Self-citations to Adlam (2022a, 2022b) are used to characterize prior constraint-based views and to flag standard features of the Page-Wootters formalism; the central argument does not reduce to those citations as authority. The Newman-objection discussion draws out consequences of the proposed modal structuralist definition rather than covertly fitting data or assuming the conclusion. No step exhibits the specific kind of reduction that would constitute circularity.

Assumptions & free parameters 0 free parameters · 6 assumptions · 0 invented entities

The paper introduces no free parameters and no new physical entities; the posits are philosophical interpretations of existing formalisms. Its central claim rests on the listed interpretive assumptions, most importantly that formal derivation order maps to ontological priority. The internal-view account is a philosophical framework, not an empirical model.

assumptions (6)
  • domain assumption Histories related by diffeomorphisms are physically identical; the symmetry is a redescription rather than a physical transformation.
    Invoked in Section 3 to restore determinism and to conclude that local coordinate functions are not physically real.
  • domain assumption Partial observables are not individually real; only complete observables are real.
    Adopted from Rovelli (2002) and Rickles (2008); it is the interpretive core that makes non-modal features derivative.
  • ad hoc to paper The order of mathematical derivation licenses ontological priority of relations over relata.
    Section 3.1: 'we can't think of the correlation as merely describing those events, since the coincidence events depend on the function...' This is the pivotal inference from formalism to metaphysics.
  • domain assumption Canonical quantization, which applies constraints to states rather than histories, is an appropriate route to quantum gravity, so relational structure rather than spacetime is fundamental.
    Section 3.2, citing Wallace (2002) on Dirac quantization; needed to strengthen the modal reading in the quantum case.
  • domain assumption A perspective-neutral state plus a choice of reference frame provides a coherent account of internal views, despite open clock-ambiguity and preferred-basis problems.
    Sections 3.2 and 4.3; the author explicitly notes these problems but proceeds on the assumption that the conceptual insight survives.
  • domain assumption Structuralist individuation of properties: a property is what it is in virtue of its place in modal structure, making its relations metaphysically necessary.
    Section 4.1, used to argue that partial observables must stand in the relations they do.

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Cite this review

Pith. "Pith review of Relational Observables, Quiddities, and Structural Realism." pith.science (2026). https://pith.science/paper/BZ76OKHF

@misc{pith2026250720313,
  author       = {Pith},
  title        = {Pith review of: Relational Observables, Quiddities, and Structural Realism},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/BZ76OKHF}},
  note         = {Machine review of arXiv:2507.20313}
}
read the original abstract

In this article, I argue that modern spacetime physics causes problems for a number of traditional accounts of modality, but also offers important new ideas about the connection between modal and non-modal features of reality. I suggest that recent work on relational observables in general relativity and quantum gravity can help us understand how non-modal features of reality could arise from modal features of reality within some form of modal ontic structural realism. In particular, I argue that the notion of an `internal view,' as employed in the partial/complete observables formalism and the quantum reference frame formalism, is an important conceptual insight which can help address outstanding problems in the philosophy of lawhood and modality.

Discussion (0). Continue with ORCID to comment.

Reference graph

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Reviewed August 6, 2026 · model on record in the stance chip above.