REVIEW 2 major objections 4 minor 1 cited by
Relational EPR
T0 review · 2 major / 4 minor · reviewed 2026-08-28 · deepseek-v4-flash
Pith's one-line read EPR correlations need no nonlocality, a relational reading says.
desk verdict A clear and honest relational reading of EPR that makes a strong claim, but the demonstration only covers the equal-setting case; the general Bell scenario is asserted rather than derived. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing device is the relative state: the quantum state of a system is not an intrinsic property but a coding of the information one system has obtained about another through past interactions, updated only on interaction. This is paired with the postulate that quantum events relative to distinct observers cannot be juxtaposed into a single account, and with a weak operational definition of separability based on 'individual observables' measurable on only one subsystem. Together these let the paper reinterpret the singlet correlations as an inference about future causally-connected interactions, not a simultaneous reality in two distant places.
What would settle it
The decisive check is formal: write a complete relative-state model of a Bell experiment in which both detectors and their pointer variables are quantum systems, update all states locally upon each interaction, and verify that the reduced statistics for later comparison of records reproduce the anti-correlations; if a consistent model can only be obtained by introducing an observer for whom both distant outcomes are simultaneously actual, the relational explanation fails.
Extended reading notes
Core claim
The central claim is that the EPR correlations have a local explanation if every system, including detectors and observers, is treated as a quantum system and every event as relative to a specific observer. For a spin-singlet pair, observer A's measurement of particle α at time t0 changes only A's relative state of β: it lets A predict what A will later measure on β or on B's pointer, not what is real at B's distant location. No event involving β happens at t0 for A, so nothing propagates instantaneously. The consistency of later comparisons of records follows from the quantum formalism, and the only failure is the attempt to compare outcomes that are actual relative to different observers. Thus, the EPR argument is turned into a challenge to strong realism rather than to locality.
Load-bearing premise
The argument rests on the postulate that a property or event is real only relative to the observing system, and that facts relative to different observers cannot be combined into one absolute description; reject that postulate and the claimed reconciliation of locality with EPR correlations does not follow.
Editorial extensions
If this is right
- EPR-type experiments no longer demonstrate a physical nonlocality; the observed correlations are compatible with locality.
- Quantum mechanics can be regarded as complete in the relational sense, while any single observer's account is acknowledged to be incomplete.
- The paradox depends on treating the measuring apparatus B as a classical system with objective pointer values; treating B as quantum removes the paradox.
- Different observers' descriptions of the same experiment are internally consistent and can be reconciled only through later causal contact, never by juxtaposing their relative facts.
- The EPR argument's lasting conclusion is directed against strong realism, not against locality.
Reading between the lines
- The same relational move should apply to other no-go results: any theorem whose premises include fixed, observer-independent outcomes in space-like separated regions would be reinterpreted as blocking that premise rather than as establishing nonlocality.
- One testable extension is to construct a fully quantum simulation of a Bell experiment with detectors modeled as quantum memory registers and check whether local relative-state updates alone reproduce the joint statistics; if such a simulation is impossible without a super-observer, the claim would be weakened.
- If correct, the relational account implies that searches for nonlocal influences, retrocausality, or superluminal signaling as explanations of entanglement are unnecessary; the correlations are a feature of the observer-relative information structure.
- The interpretation suggests a precise formal project: develop a consistent multi-observer relative-state calculus, possibly including relativistic observers, in which consistency conditions like pointer-readback hold by construction.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper argues that, within the relational interpretation of quantum mechanics (RQM), the EPR correlations do not require any form of non-locality. The central idea is that facts are only real relative to a specific observer, that all systems including observers and detectors are quantum, and that relative facts belonging to different observers cannot be juxtaposed. On this basis, the paper reinterprets the EPR argument and Bell-type non-locality proofs as resting on an unjustified assumption of observer-independent actuality. It then presents a consistency calculation, for the case where both observers measure spin in the same direction, showing that a later observer who compares the pointer variables sees anti-correlated results. The paper concludes that RQM reconciles quantum mechanics with locality, completeness, and an operational notion of separability, and it contrasts this position with Laudisa's earlier relational treatment of EPR.
Significance. If the central claim were fully established, the paper would be a significant contribution to the debate on Bell correlations, offering a coherent interpretive route to saving locality at the price of Einsteinian strong realism. The manuscript is explicit that its conclusion is conditional on adopting the RQM postulate that relative facts of different observers cannot be juxtaposed (Section 4.4), and the same-direction consistency calculation in Section 4.3 is transparent and standard. The paper also engages seriously with prior work by Laudisa and Peres. However, its advertised conclusion is broader than the demonstrated calculation: the general Bell/CHSH scenario with independent settings is never treated, and the notion of locality used is essentially no-signaling rather than the factorizability notion constrained by Bell's theorem. The paper is therefore a worthwhile contribution to the interpretive literature, but the main claim needs additional technical and conceptual support.
major comments (2)
- [§4.3 (Eqs. (6)–(9))] The consistency calculation is carried out only for the case n=n'=z. The operative content of 'EPR correlations' in the modern debate is the full Bell/CHSH correlation table for independently chosen settings, and for unequal settings the relative state of the pointer variables of A and B is not the simple anti-correlated state used in Eqs. (6)–(9). The paper never writes the state relative to a later observer C for n≠n', nor does it show how the Bell/CHSH joint probabilities emerge in the relational account. Unless the same-setting case is explicitly argued to be sufficient, the abstract's and Introduction's conclusions that EPR correlations 'do not entail any form of non-locality' outrun the demonstration.
- [§2.3 and §4.3] Section 2.3 defines locality as the absence of instantaneous mutual influence, which is essentially a no-signaling condition. Bell's theorem, however, constrains a different notion: the factorizability of joint conditional probabilities over outcomes that are available in a single observer's later record comparison. The paper shows that no faster-than-light influence passes between A and B, but this does not by itself show that the final observer's joint account of the two pointer readings satisfies Bell locality. The manuscript should either prove the relevant factorizability (or equivalent condition) for arbitrary settings, or explicitly state that 'locality' is being used in a non-Bell sense. As written, the reconciliation with 'locality' as used in the EPR debate is asserted rather than demonstrated.
minor comments (4)
- [§4.3, Eq. (9)] The density matrix in Eq. (9) is misprinted: the second term repeats the first term, but it should read |↑⟩_A |↓⟩_B ⟨↑|_A ⟨↓|_B.
- [§4.2, Eqs. (2)–(3)] The text introduces the observable S^{n'}_{Aβ}, but Eq. (3) states S^{n}_{Aβ} = -ε. Since this equality holds only when n'=n, the notation should make this restriction explicit.
- [§4.1] The unqualified statement that no observer can have both outcomes actual is in tension with the later-observer comparison in Section 4.3; it should be qualified as applying to spacelike separation before the observers come into causal contact.
- [§3.4] The historical claim that all analyses leading to Bell-type non-locality maintain an objective element of reality in the simultaneous realization of results is stated without a survey; specifying which premise of a particular theorem (e.g., Stapp's or Hardy's) is being rejected would sharpen the argument.
Circularity Check
The paper's reconciliation of EPR correlations with locality is largely definitional: it defines 'locality' relationally and stipulates that distinct observers' facts cannot be juxtaposed, which removes Bell-type non-locality by construction rather than by derivation.
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self definitional
[Section 2.3 and Section 3.4]
"We call locality the principle demanding that two spatially separated events cannot have instantaneous mutual influence. ... But the core assumption of RQM is that quantum events relative to distinct observers cannot be simply juxtaposed."
The argument equates 'locality' with absence of instantaneous influence between events relative to a single observer, and simultaneously adopts the RQM rule that facts relative to distinct observers cannot be juxtaposed. Bell-type non-locality, however, is a constraint on a joint probability distribution over outcomes that are later brought together at one observer; the paper's premises rule out the very object to which Bell inequalities apply. The conclusion that EPR correlations 'do not entail any form of non-locality' is therefore contained in the definition of locality and in the no-juxtaposition postulate, rather than derived from the quantum formalism.
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renaming known result
[Section 2.4 and Section 4]
"This notion of separability is equivalent to a minimal operational definition of subsystems of a composite system. It is deliberately weak (and in the end trivial); any stronger definition testifies to some unnecessary unease. ... Incontestably, both get definite outcomes during these complete measurements (in the sense of Dirac). Hence, the particles are separable."
The paper first redefines separability as the existence of individual observables actualized by local measurements, calling this 'deliberately weak (and in the end trivial)'. Later it infers from the fact that both detectors obtain definite outcomes that 'the particles are separable'. This conclusion is true by the stipulated definition, not by the EPR/Bell notion of non-separability; the move merely renames the uncontroversial fact of definite outcomes and thereby dismisses the non-separability alternative without argument.
full rationale
This is a philosophical paper whose conclusion is explicitly conditional on adopting RQM. The conditional character mitigates the circularity: the authors say the aim is 'not to defend explicitly the relational interpretation ... but only to remark that, if one adopts this view, the disturbing non-local features ... disappear.' However, within that conditional the central claim is substantially definitional. The paper defines locality as absence of instantaneous mutual influence relative to a given observer and stipulates, as the 'core assumption of RQM', that facts relative to distinct observers cannot be juxtaposed. Bell-type non-locality is exactly a constraint on juxtaposed outcomes, so the premises remove the target phenomenon by construction. The only consistency calculation (Section 4.3) treats equal settings and shows that a later observer sees correlated pointers; it never derives the general Bell/CHSH correlation table for unequal settings from the perspective of an observer who has compared the records. A second, less central redefinition occurs for separability: the paper defines it operationally as the existence of individual observables and then declares the particles separable because each detector gets a definite outcome. This is renaming a trivial operational fact rather than addressing the EPR/Bell non-separability debate. The RQM postulate is imported from the first author's earlier work, but because the paper explicitly treats RQM as an adopted viewpoint rather than a proven premise, I do not count the self-citation as an additional load-bearing circular step. Overall, the paper's positive consistency calculation is real but narrow; the strong reconciliation claim reduces, to a significant degree, to the paper's definitions.
Assumptions & free parameters
assumptions (5)
- domain assumption Quantum mechanics is a theory about the physical description of physical systems relative to other systems, and this is a complete description of the world.
- domain assumption All systems are quantum; there are no intrinsically classical systems.
- domain assumption Facts relative to different observers cannot be juxtaposed.
- domain assumption Locality defined as: two spatially separated events cannot have instantaneous mutual influence.
- standard math Standard quantum measurement formalism (projection postulate, trace, density matrices).
Cite this review
Pith. "Pith review of Relational EPR." pith.science (2026). https://pith.science/paper/MPXDIK3X
@misc{pith2026quant-ph0604064,
author = {Pith},
title = {Pith review of: Relational EPR},
year = {2026},
howpublished = {\url{https://pith.science/paper/MPXDIK3X}},
note = {Machine review of arXiv:quant-ph/0604064}
}
read the original abstract
We study the EPR-type correlations from the perspective of the relational interpretation of quantum mechanics. We argue that these correlations do not entail any form of 'non-locality', when viewed in the context of this interpretation. The abandonment of strict Einstein realism implied by the relational stance permits to reconcile quantum mechanics, completeness, (operationally defined) separability, and locality.
Forward citations
Cited by 1 Pith paper
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Weak Values and Relational Generalisations
The paper casts weak values as conditional probabilities in a Coxian Bayesian histories formalism, using complex 'peg' assignments.
Reference graph
Works this paper leans on
-
[1]
Experimen- tal test of Bell’s inequalities using time-varying ana- lyzers
A. Aspect, J. Dalibard, G. Roger, “Experimen- tal test of Bell’s inequalities using time-varying ana- lyzers” Phys. Rev. Lett. 49, 1804-1807 (1982)
work page 1982
-
[2]
A. Aspect, P. Grangier, G. Roger, “Ex- perimental realization of Einstein-Podolsky-Rosen gedankenexperiment: a new violation of Bell’s in- equalities” Phys. Rev. Lett. 49, 91-94 (1982)
work page 1982
-
[3]
C. J. Isham, Lectures on Quantum Theory: Mathe- matical and Structural Foundations , Imperial College Press, London, 1995
work page 1995
-
[4]
Non-locality for two particles without in- equalities for almost all entangled states
L. Hardy, “Non-locality for two particles without in- equalities for almost all entangled states” Phys. Rev. Lett. 71, 1665-1668 (1993)
work page 1993
-
[5]
A Bell-type theorem without hidden variables
H. P. Stapp, “A Bell-type theorem without hidden variables” Am. J. Phys. 71, 30-33 (2004)
work page 2004
-
[6]
C. Rovelli, “Relational quantum mechanics” Intl. J. Theor. Phys. 35, 1637-1678 (1996)
work page 1996
-
[7]
F. Laudisa, C. Rovelli, “Relational quantum mechanics” in The Stanford En- cyclopedia of Philosophy , E. N. Zalta ed.; http://plato.stanford.edu/entries/qm-relational/
-
[8]
A. Grinbaum, The Significance of Information in Quantum Theory, PhD thesis, Ecole Polytechnique, Paris, 2004
work page 2004
Show all 35 references
-
[9]
Non-representationalist theories of knowledge and quantum mechanics
M. Bitbol, “Non-representationalist theories of knowledge and quantum mechanics” SATS (Nordic journal of philosophy) 2, 37-61 (2001)
2001
-
[10]
Remarques on relational quantum me- chanics
M. Bitbol, “Remarques on relational quantum me- chanics” 2004, unpublished
2004
-
[11]
van Fraassen, ”Rovelli’s world,” 2006, unpub- lished
B. van Fraassen, ”Rovelli’s world,” 2006, unpub- lished
2006
-
[12]
Rovelli, Quantum Gravity , Section 5.6, Cam- bridge University Press, Cambridge, 2004
C. Rovelli, Quantum Gravity , Section 5.6, Cam- bridge University Press, Cambridge, 2004
2004
-
[13]
Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?
A. Einstein, B. Podolsky, N. Rosen, : “Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?” Phys. Rev. 47, 777-780 (1935)
1935
-
[14]
The EinsteinPodolskyRosen physical re- ality is completely rescued by quantum mechanics
D. Page, “The EinsteinPodolskyRosen physical re- ality is completely rescued by quantum mechanics” Phys. Lett. 91A, 57 (1982)
1982
-
[15]
On the problem of hidden variables in quantum mechanics
J. S. Bell, “On the problem of hidden variables in quantum mechanics” Rev. Mod. Phys. 38, 447-452 (1966)
1966
-
[16]
The problem of hidden variables in quantum mechanics
S. Kochen, E. Specker, “The problem of hidden variables in quantum mechanics” J. Math. Mech. 17, 59-87 (1967)
1967
-
[17]
d’Espagnat, Une incertaine r´ ealit´ e, Gauthier- Villars, Paris, 1985
B. d’Espagnat, Une incertaine r´ ealit´ e, Gauthier- Villars, Paris, 1985
1985
-
[18]
Rovelli, Quantum Gravity , Cambridge Univer- sity Press, Cambridge 2004
C. Rovelli, Quantum Gravity , Cambridge Univer- sity Press, Cambridge 2004
2004
-
[19]
An analysis of the Einstein-Podolsky- Rosen correlations in terms of events
M. Bitbol, “An analysis of the Einstein-Podolsky- Rosen correlations in terms of events” Phys. Lett. A 96, n 2, 66-70 (1983)
1983
-
[20]
C. A. Fuchs, Quantum Foundations in the Light of Quantum Information, in Proceedings of the NATO Advanced Research Workshop on Decoherence and its Implications in Quantum Computation and Informa- tion Transfer, edited by A. Gonis, IOS Press, Ams- terdam, 2001
2001
-
[21]
E. T. Jaynes, Clearing up mysteries - the original goal, opening talk at the 8’th International MAXENT Workshop, ST. John’s College, Cambridge, Eng- land, August 1-5, 1988, in Mawimum Entropy and Bayesian Methods , J. Skilling editor, Kluwer Aca- demic, Dordrecht, 1989, pp. 1-27
1988
-
[22]
Information Flow in Entangled Quantum Systems
D. Deutsch, P. Hayden, “Information Flow in Entangled Quantum Systems”, preprint arXiv: quant-ph/9906007
-
[23]
Einstein, Podolsky, Rosen, and Shan- non
A. Peres, “Einstein, Podolsky, Rosen, and Shan- non” Found. Phys. 35, 511-514 (2004)
2004
-
[24]
Physics, philosophy and scientific progress
A. Einstein, “Physics, philosophy and scientific progress” J. Int. Coll. Surg. 14, 755-758 (1950)
1950
-
[25]
Fine, The Shaky Game: Einstein Realism and the Quantum Theory , University of Chicago Press, Chicago, 1996 9
A. Fine, The Shaky Game: Einstein Realism and the Quantum Theory , University of Chicago Press, Chicago, 1996 9
1996
-
[26]
Wittgenstein, Tractatus Logico-Philosophicus, Routledge and Kegan Paul, London, 1922
L. Wittgenstein, Tractatus Logico-Philosophicus, Routledge and Kegan Paul, London, 1922
1922
-
[27]
The philosophy of Niels Bohr
A. Petersen, “The philosophy of Niels Bohr” Bull. Atom. Sci. 19, n 7, 8-14
-
[28]
Quantum probabilities as Bayesian probabilities
C. M. Caves, C. A. Fuchs, R. Schack, “Quantum probabilities as Bayesian probabilities” Phys. Rev. A 65, 022305
-
[29]
Lorentz transformations of open systems
A. Peres, D. R. Terno, “Lorentz transformations of open systems” Journ. Mod. Opt. 49, n 8, 1255-1261 (2002)
2002
-
[30]
P. A. M. Dirac, Principles of Quantum Mechanics , Oxford University Press, Oxford, 1930
1930
-
[31]
Einstein on Locality and Separability
D. Howard, “Einstein on Locality and Separability” Stud. Hist. Phil. Sci. 16, 171-201 (1985)
1985
-
[32]
Aspect, Reception speech, Acad´ emie des Sci- ences, Paris (2002)
A. Aspect, Reception speech, Acad´ emie des Sci- ences, Paris (2002)
2002
-
[33]
Are classical probabilities instances of quantum amplitudes?
I. Vecchi, “Are classical probabilities instances of quantum amplitudes?””, preprint arXiv: quant-ph/0206147
-
[34]
The EPR Argument in a Relational In- terpretation of Quantum Mechanics
F. Laudisa “The EPR Argument in a Relational In- terpretation of Quantum Mechanics” Found. Phys. Lett. 14, 119-132 (2001)
2001
- [35]
Reviewed August 28, 2026 · model on record in the stance chip above.
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