What Kind of Relationality does Quantum Mechanics Exhibit?

Emily Adlam

REVIEW 3 major objections 3 minor 1 cited by

What Kind of Relationality does Quantum Mechanics Exhibit?

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

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Pith's one-line read The paper argues that relational quantum mechanics should be read as making quantum states relative while measurement facts remain absolute and shareable.

desk verdict A clear taxonomy of relational quantum mechanics and a promising but promissory case for RQM+CPL as inherently dynamical; the central ontology of absolute occurrent conditions remains unformalized. read the letter →

arxiv 2502.06991 v1 pith:EYTD4I32 submitted 2025-02-10 quant-ph physics.hist-ph

Emily Adlam This is my paper · ORCID

classification quant-phphysics.hist-ph

keywords relationalquantummechanicsWigner'sfriendparadoxcross-perspectivelinksinherent-dynamicalrelationalisminteractionstatesoccurrentconditionsintersubjectivitymeasurementproblem

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 for a middle position in the interpretation of quantum mechanics: quantum states are genuinely relational—they describe how one system would interact with another—but the facts about what an observer actually sees are not relational. The view, called RQM+CPL, combines the relational quantum mechanics tradition with a new postulate saying that measurement results can be shared across observers through physical interactions. The author's central claim is that this combination fills a previously empty slot in the space of relational interpretations and handles the friend-and-outside-observer paradox without relativizing facts. If correct, it gives relational quantum mechanics a coherent epistemology: observers can confirm each other's outcomes, can know their own experiences, and are not trapped in an infinite regress of perspectives.

What carries the argument

The central machinery is a two-way classification of relational approaches—effective versus inherent relationality, and dynamical versus fact-based relationalism—together with the distinction between an interaction state (a modal description of possible future interactions, relativized to an observer) and an occurrent condition (the non-modal, absolute facts about what is actually the case). The paper slots RQM+CPL into the inherent-dynamical cell: quantum states are always relational, but they encode only dispositions, so incompatible states relative to different observers can coexist while a single absolute set of occurrent conditions settles what actually happens. The cross-perspective links postulate carries the load: it asserts that if one observer measures a variable and retains the record, any other observer who later measures that record gets the same value, making outcome facts absolute and shareable.

What would settle it

A concrete ontology for RQM+CPL would be falsified if one could prove a no-go theorem that any single-world, first-person-universal theory with absolute Cross-Perspective Links is incompatible with the statistical predictions of unitary quantum mechanics. Short of that, an experimental demonstration that a measurement record can be erased or repurposed so that no later observer can ever recover the original outcome, even in principle, would undercut the claim that measurement facts are absolute and shareable.

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Extended reading notes

Core claim

The central claim is that RQM+CPL is naturally understood as a form of inherent-dynamical relationalism: the relativization of quantum states is an inherent feature of quantum mechanics, but this relativization applies to dynamics rather than to facts. On this reading, a quantum state is an interaction state—a modal description of possible future interactions relativized to a particular observer—and such states can legitimately differ from observer to observer. Behind them sit absolute occurrent conditions: non-modal facts about which measurement outcomes actually occur. The cross-perspective links postulate asserts that, provided no information is destroyed, any observer who later measures the record of a measurement will find the same outcome, so these absolute facts are empirically accessible. The paper argues this dissolves the friend paradox, avoids the regress of relativization, and makes relational quantum mechanics confirmable by ordinary scientific practice.

Load-bearing premise

There exists a coherent set of absolute facts, independent of any observer's quantum description, about what actually happened in a measurement, and observers can learn those facts; the paper leaves the nature of those facts unspecified.

Editorial extensions

If this is right

If RQM+CPL is right, observers can in principle verify each other's measurement outcomes, so relational quantum mechanics is not self-undermining as an empirical theory.
An observer's own experience is authoritative: an outside observer's superposition description does not imply the original observer's outcome is indeterminate, because the outside interaction state is not a complete description of the original observer's occurrent condition.
Observers can know their own condition without assigning themselves a quantum state, avoiding the infinite relativization regress that threatens Orthodox RQM.
The extended friend–outsider no-go theorems do not force a relativization of observed events: RQM+CPL keeps absolute outcomes and responds by accepting nonlocality and retrocausality.
The approach opens a previously empty cell in the landscape of interpretations, between fact-based relationalism and effective-dynamical views such as many-worlds and pilot-wave approaches.

Reading between the lines

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

My inference: the paper leaves the ontology of occurrent conditions open, so a completed version will likely require adding a layer of actual-valued variables or primitive records to the formalism, probably from physics beyond non-relativistic quantum mechanics.
My inference: if absolute occurrent conditions exist, the measurement problem in RQM+CPL becomes the problem of specifying when and how variables become definite, suggesting a research program for constructing effective collapse-like dynamics from relational states.
My inference: the two-axis classification suggests a comparative question—whether the nonlocal, retrocausal structure required by RQM+CPL can be realized in an explicit model; if no such model exists, the view's consistency would be in doubt.

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Editorial analysis

A structured set of objections, weighed in public.

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

Desk Editor's Note

read the letter

Colleague — the thing to know: this paper gives a genuinely useful four-way classification of relational quantum mechanics (effective/inherent × fact/dynamical) and argues, convincingly for the most part, that Adlam and Rovelli's RQM+CPL occupies the inherent-dynamical cell. That classification is new, and it does real work: it isolates why Orthodox RQM generates epistemic self-undermining problems and why dynamical relationalism can avoid them without going Everettian. The discussion of the extended Wigner's friend theorems is also a genuine contribution — the point that both tame and feral relationalism end up rejecting absolute CPL, and the real issue is CPL itself, is well taken.

What I like: the paper is unusually clear about its own commitments. It explicitly states that the ontology of absolute occurrent conditions is not written down and would require physics beyond nonrelativistic QM (Section 3.2). That is not buried. The arguments against Orthodox RQM about intersubjectivity, ownership of experience, and self-knowledge are philosophically substantive, and they engage directly with Rovelli's RCPL move. The reply to the regress of relativization is also fair: it correctly identifies that the regress only goes through if you read occurrent conditions directly off interaction states.

The soft spots are real, though. The central load-bearing notion — absolute, non-relativized occurrent conditions distinct from quantum states — is left at the level of stipulation. The paper's own modal-interpretation analogy cuts against it: as Section 2.1 notes, you cannot in general calculate a value state from a quantum state when multiple incompatible quantum states are associated with the same value state, and RQM+CPL is exactly that case. So the advantages over Orthodox RQM are promissory: they hold only if such an ontology can be made coherent. The circularity concern is also fair: the definitions of 'interaction state' and 'occurrent condition' are chosen so that RQM+CPL lands in the favorable cell. That isn't disqualifying, but it means the paper is better as a research program than a finished theory.

Who is this for: philosophers of physics and RQM partisans. A serious referee should engage with it. It deserves peer review, not desk rejection, because the taxonomy and the sharpening of the CPL debate are valuable even if the ontology remains open.

Referee Report

3 major / 3 minor

Summary. The paper elaborates the Adlam–Rovelli proposal RQM+CPL and argues that it should be understood as an inherent-dynamical form of relationalism. On this picture, quantum states are always relational interaction states, while there exist absolute, non-relativized occurrent conditions that include facts about measurement outcomes. The paper motivates this position by contrasting inherent vs. effective and dynamical vs. fact-based relationalism, compares RQM+CPL with Orthodox RQM, and claims advantages for intersubjectivity, ownership of experience, and self-knowledge. It then responds to objections based on the regress of relativization and on the extended Wigner's Friend theorems.

Significance. The paper fills a real gap in the logical space of relational interpretations and clearly articulates a position that is often gestured at but not developed: relational quantum states without relative facts. It engages seriously with the main objections in the recent literature, including Rovelli's regress argument, Riedel's iteration argument, and the EWF no-go theorems. The writing is clear and the conceptual distinctions are useful. However, the central ontological posit—absolute occurrent conditions distinct from interaction states—is left unformalized, and the author explicitly concedes that a concrete ontology is an outstanding problem. Since the claimed advantages over Orthodox RQM are argued to follow from these occurrent conditions, the paper's main conclusion is currently promissory rather than established.

major comments (3)

[§3.2] The central posit of absolute, non-relativized occurrent conditions is not given any formalism or dynamical principle. The paper explicitly states that 'writing down a concrete ontology for an inherent-dynamical approach would not be straightforward' (§3.2). This is not a peripheral caveat: the advantages claimed in §4.1–4.3 all rely on observers having access to occurrent conditions that are distinct from, and not determined by, their interaction states. As written, the paper does not supply a consistency check or even a toy model showing that an ontology satisfying CPL can reproduce the Wigner–Friend unitary statistics described in §2 while also supporting the absolute cross-perspective links. This gap is load-bearing for the central claim that RQM+CPL is a coherent alternative to Orthodox RQM.
[§2.1] The modal-interpretation analogy does not provide the support the paper claims. The paper notes that modal interpretations typically 'provide a prescription which allows us to calculate probabilities for the value state directly from a quantum state,' but then observes that 'such a calculation will not in general be possible if we allow that there may be multiple incompatible quantum states associated with a given value state.' RQM+CPL is exactly such a case: Alice and Bob can assign incompatible interaction states to the same system at the same time (§3.1). Thus the analogy highlights that occurrent conditions are not derivable from, or even constrained by, the quantum formalism. The paper needs to say what physical facts or principles determine the occurrent condition; otherwise the classification of RQM+CPL as a 'dynamical' view is not yet a worked-out theory.
[§5.1] The rebuttal of Rovelli's regress argument consists in denying that occurrent conditions can be read off interaction states. That denial is precisely the disputed premise between dynamical and fact-based relationalism. To make the rebuttal non-question-begging, the paper needs a positive account of how the absolute occurrent condition is fixed in the Wigner–Friend scenario—for instance, what distinguishes the branch where Alice obtains 0 from the branch where she obtains 1 when the interaction state relative to Bob is the same superposition. Without such an account, the response to the regress is a restatement of the proposed distinction rather than an argument that the distinction is coherent.

minor comments (3)

[§4.2] In the Wigner–Friend example, the superposition is written as 'a|0⟩S|0⟩A + b|0⟩S|0⟩A' where the second term should be b|1⟩S|1⟩A; this appears to be a typographical error.
[§2] Several typographical errors remain, including 'mecahnics' in the paragraph beginning 'We can certainly still say that there is an absolute fact...'; a careful proofread is needed.
[§5.2] The statement that RQM+CPL should probably be understood as both non-local and retrocausal is important and is not defended in this paper; since it is said to be 'already baked into' Adlam and Rovelli (2023), a forward reference with a two-sentence explanation would help the reader understand how this commitment interacts with the absolute CPL postulate.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the paper elaborates a prior proposal and classifies it by stipulation, but the central arguments are independent of the cited prior work.

full rationale

I find no circular step that meets the quoted-reduction standard. The paper is a philosophical elaboration of RQM+CPL, a proposal introduced in Adlam and Rovelli (2023), and it defines its own taxonomy of relational approaches in Section 2. The classification of RQM+CPL as an inherent-dynamical view in Section 3.1 follows from the definitions and postulates the paper itself adopts, but this is conceptual taxonomy rather than a derivation of empirical content. The claimed advantages over Orthodox RQM in Sections 4.1-4.3 are argued from independent epistemic premises about intersubjectivity, ownership of experience, and self-knowledge; they do not reduce to the citation to Adlam and Rovelli (2023). The paper explicitly flags a serious outstanding limitation in Section 3.2: 'writing down a concrete ontology for an inherent-dynamical approach would not be straightforward, and would likely require appealing to physics beyond standard non-relativistic quantum mechanics.' This is a substantive gap in the proposal, and the claimed epistemic advantages are therefore promissory, but it is a limitation of the view rather than a circularity in the argument. The self-citations present in the paper are background and motivation, not load-bearing reductions. No fitted parameter is renamed as a prediction, no uniqueness theorem is imported from the authors' prior work, and no known result is merely renamed as an organizing scheme. The paper's central claim is therefore not forced by its own inputs; it rests on an unformalized ontology whose absence is admitted rather than hidden. That absence is a correctness risk, not a circularity.

Assumptions & free parameters 0 free parameters · 7 assumptions · 1 invented entities

The central claim depends on a set of interpretive postulates inherited from RQM, plus the Cross-Perspective Links postulate and the existence of absolute occurrent conditions. No free parameters are fitted because the paper is conceptual. The occurrent-conditions entity is the main invented addition, and it is not independently evidenced.

assumptions (7)

domain assumption First-person universality: every observer's predictions are obtained by unitary evolution and the Born rule applied to their own measurements (Postulate 4).
Adopted from RQM as a founding premise; it motivates why different observers can assign different states to the same system.
domain assumption No Anthropocentricism: any physical system can serve as an observer (Postulate 1).
Defines RQM broadly; used to avoid privileging conscious observers.
domain assumption Measurement postulate: in any physical interaction, a variable becomes definite relative to the other system (Postulate 3).
Standard RQM postulate; the paper notes the identification of measurements is not fully specified.
domain assumption Single-world: observers do not branch upon measurement (Postulate 5).
Distinguishes RQM+CPL from Everett; needed for the CPL equality.
ad hoc to paper Cross-Perspective Links: if Alice measures a variable and nothing erases her record, Bob's later measurement of Alice's record matches Alice's outcome (Postulate 6).
Introduced by Adlam and Rovelli (2023) to create shared facts; this paper treats it as a defining postulate of RQM+CPL without derivation.
ad hoc to paper Existence of absolute occurrent conditions distinct from quantum states.
Assumed to give RQM+CPL its epistemic advantages; explicitly unformalized in Section 3.2.
ad hoc to paper Quantum states are interaction states, describing modal facts about possible interactions rather than occurrent conditions.
This interpretative claim is central to the paper's taxonomy and is argued for, not proven, in Sections 2-3.

invented entities (1)

Occurrent conditions (absolute, non-relativized facts about measurement outcomes)
purpose: Provide a stable ground truth that observers can share and know, avoiding the epistemic problems of Orthodox RQM.
No empirical handle is given; the paper says deriving a concrete ontology requires physics beyond standard QM (Section 3.2).

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Cite this review

Pith. "Pith review of What Kind of Relationality does Quantum Mechanics Exhibit?." pith.science (2026). https://pith.science/paper/EYTD4I32

@misc{pith2026250206991,
  author       = {Pith},
  title        = {Pith review of: What Kind of Relationality does Quantum Mechanics Exhibit?},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/EYTD4I32}},
  note         = {Machine review of arXiv:2502.06991}
}

read the original abstract

In this article I elaborate on the approach to relational quantum mechanics suggested by Adlam and Rovelli (2023). I suggest that this approach fills an important gap in the spectrum of relational approaches, because it posits that the relational aspects of quantum mechanics are both inherent and dynamical. I compare this approach to Orthodox RQM, arguing that it has a number of advantages, and I show how some possible objections can be resolved.

Discussion (0). Continue with ORCID to comment.

Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

Adlam's Frame: comment on "Wigner's Frame"
quant-ph 2026-07 conditional novelty 6.0 of 10

Quantum reference frames do not evade the Wigner's-friend no-go theorems: the proposed resolution alters quantum theory and measures a substituted observable, not the friend's outcome.

Reference graph

Works this paper leans on

39 extracted references · 33 canonical work pages · cited by 1 Pith paper

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Pith tools

Reviewed August 8, 2026 · model on record in the stance chip above.

[1] [1]

Adlam, E. (2014). The Problem of Confirmation in the Everett Interpretation . Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics , 47:21 -- 32

work page 2014

[2] [2]

Adlam, E. (2022). Does Science need Intersubjectivity? The Problem of Confirmation in Orthodox Interpretations of Quantum Mechanics . Synthese

work page 2022

[3] [3]

Adlam, E. (2024). Moderate physical perspectivalism. Forthcoming in Philosophy of Science

work page 2024

[4] [4]

and Rovelli, C

Adlam, E. and Rovelli, C. (2023). Information is physical: Cross-perspective links in relational quantum mechanics. 1

work page 2023

[5] [5]

and Dickson, M

Bacciagaluppi, G. and Dickson, M. (1999). Dynamics for modal interpretations. Foundations of Physics , 29(8):1165--1201

work page 1999

[6] [6]

and Dieks, D

Bene, G. and Dieks, D. (2001). A perspectival version of the modal interpretation of quantum mechanics and the origin of macroscopic behavior. Foundations of Physics , 32(5):645--671

work page 2001

[7] [7]

G., Pryde, G

Bong, K.-W., Utreras-Alarc \' o n, A., Ghafari, F., Liang, Y.-C., Tischler, N., Cavalcanti, E. G., Pryde, G. J., and Wiseman, H. M. (2020). A strong no-go theorem on the Wigner's friend paradox . Nature Physics , 16(12):1199--1205

work page 2020

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Brukner, C . (2017). On the Quantum Measurement Problem , pages 95--117. Springer International Publishing, Cham

work page 2017