1. Introduction

The question of whether a human being could live in a "quantum reality"—a reality in which the world one experiences is constituted entirely by one's own observation, and in which other people are only observed contents of that experience rather than independent centres of life and death—is not a single question but a knot of several. It draws together the measurement problem in quantum mechanics, the long philosophical tradition of solipsism, and the ordinary but strangely under-examined fact that death is never something a person can report from the inside. The motivating puzzle is easy to state in the first person and surprisingly hard to state in the third: if all I ever have access to is what appears in my own experience, then the death of another person is, for me, an event within my observation, while my own death is an event that—by definition—I never observe. From this asymmetry the stronger claim is sometimes inferred: that I never die, that others' deaths are only phenomena in my experience, and that each person is in effect living in a private reality of their own. The report takes this inference seriously enough to examine it carefully, and its central claim is that the inference is not supported: the first-person inaccessibility of one's own death is a real and philosophically interesting limit of experience, but it does not license a quantum-mechanical solipsism, because nothing in quantum theory makes consciousness the metaphysical author of reality, and the step from an epistemic limit to an ontological conclusion is precisely where the argument fails.

Clarity about terms is therefore the first task. Quantum mechanics describes physical systems by states that, when measured, yield outcomes with probabilities given by the Born rule; the "measurement problem" is the unresolved question of how definite outcomes arise from the theory's formalism, and of what role, if any, the observer plays in that transition. It is essential to distinguish measurement in the physical sense—an interaction that correlates a system with an apparatus and leaves a record—from conscious experience, the felt awareness of an outcome. Much of the popular argument for a "quantum reality" of the first person trades on conflating these two, treating the collapse of a superposition as something a mind performs rather than something a physical interaction (or a branching, or a Bayesian updating, depending on one's interpretation) accounts for. The report accordingly treats the following dimensions as its analytical spine:

• the measurement problem and the precise sense in which observation enters quantum theory;
• the competing interpretations—Copenhagen, many-worlds, and QBism prominent among them—and whether any of them makes the observer metaphysically fundamental;
• the philosophical structure of solipsism and its proposed quantum analogue, "quantum solipsism";
• the first-person versus third-person analysis of death, including the "quantum immortality" argument;
• the empirical, logical, and ethical objections that decide the issue.

The analytical frame that organises the report is the distinction between epistemic and ontological claims about the observer. The premise that a person has privileged and inescapable access to their own experience is epistemically true but modest: it says what anyone can know, not what exists. The conclusion that other persons are "just an observed reality of himself" is ontological and immodest: it says what there is. The report's guiding thread is that every step from the first to the second must be argued for, and that the quantum vocabulary in which the step is usually dressed supplies no such argument. Interpretations of quantum mechanics disagree profoundly about what the formalism means, but none of the major interpretations identifies a person's consciousness as the entity that selects reality for that person alone; QBism comes closest to putting the agent at the centre, yet it does so in a way that makes other agents indispensable rather than illusory.

The report proceeds in five movements. It begins with the measurement problem and the observer's role, separating physical measurement from conscious experience. It then compares the major interpretations to establish what work the observer actually does in each. With that groundwork, it turns to solipsism and its quantum analogue, examining whether the claim that others are only observed realities can be made coherent. It then addresses death directly: the first-person impossibility of observing one's own non-existence, the third-person evidence that deaths occur, and the quantum immortality argument that exploits the gap between them. Finally, it assembles the empirical, logical, and ethical critiques, and explains why the strong first-person-only thesis remains a metaphysical proposal rather than a scientifically established result. The conclusion the report defends is narrow but firm: the first-person limit on observing one's own death is genuine, and quantum mechanics neither removes nor explains it.

2. Quantum Measurement and the Observer

2.1 The two-rule structure and the measurement problem

The claim that "a person is the only one noticing events happening for himself" borrows its vocabulary from quantum mechanics, so the first task is to state precisely what quantum mechanics says about observation — and what it does not. Standard quantum theory contains two dynamical rules that do not obviously fit together: smooth, deterministic, unitary evolution of the state vector under the Schrödinger equation, and the Born rule, which assigns probabilistic outcomes to measurements. The "measurement problem" is exactly this mismatch: collapse (projection) enters textbooks as an extra postulate, not as a consequence of unitary evolution [CIT-arXiv:1604.07422v2]. Frauchiger and Renner frame the stakes sharply by asking whether quantum theory can be applied to systems that include the agents using it, noting that direct tests remain largely confined to microscopic domains even though the theory is presumed almost universally valid — with Schrödinger's cat as the canonical stress test [CIT-arXiv:1604.07422v2].

This two-rule structure is the origin of the intuition behind the user's question. If collapse is triggered by "observation," and observers are conscious persons, it is a short step to the conclusion that reality is partitioned into private observational worlds. The step is not licensed by the formalism, but the formalism's ambiguity is what makes the step tempting. It is worth being explicit that the literature retrieved for this section does not contain a paper defending the strong thesis that "other persons are merely observed reality of oneself and do not really happen to them"; the closest formal relative is the observer-relative state assignment of Wigner's-friend setups, discussed below, which is a claim about state descriptions, not about the nonexistence of other minds.

2.2 Superposition, measurement, and the von Neumann chain

The mechanism that generates observer-relativity is linearity. Wigner's 1967 argument runs as follows: agent F measures a spin and, having seen outcome $z$, assigns the measured system a definite pure state; agent W, outside the isolated lab and ignorant of $z$, may instead assign the entire lab — spin, device, and friend — a macroscopic superposition, by linearity of the map $S \to L$ [CIT-arXiv:1604.07422v2]. Formally, if the lab starts in a ready state and the measurement is unitary,

$$|\psi\rangle_{\text{lab}} = \alpha,|{\uparrow}\rangle_S |D_\uparrow\rangle |F_\uparrow\rangle + \beta,|{\downarrow}\rangle_S |D_\downarrow\rangle |F_\downarrow\rangle,$$

then F's description (one branch, definite outcome) and W's description (the full superposition) are both internally consistent. This is the von Neumann chain: nothing in unitary dynamics singles out where "measurement" happens, so the cut between observer and observed can be moved outward indefinitely.

Frauchiger and Renner stress a point that is routinely lost in popular retellings: the plain Wigner's-friend setup is not a contradiction. The difference between F's pure state and W's reduced (maximally mixed) state is an ordinary consequence of entanglement and ignorance, not a paradox [CIT-arXiv:1604.07422v2]. The contradiction requires additional assumptions — notably that agents can reason about each other's reasoning and that measurement outcomes are stable facts — which is what the extended Frauchiger–Renner argument exploits. For the user's thesis, this is decisive in one direction: quantum mechanics does not say that F's death and W's observation of F's death are two incompatible realities. It says that F and W may assign different states to the same physical system, and that these assignments are related by tracing out degrees of freedom.

2.3 What "observation" means physically: decoherence and the classical limit

The physical process that makes macroscopic superpositions practically unobservable is decoherence, not consciousness. When a system entangles with a large environment, the reduced density matrix of the system rapidly loses its off-diagonal terms in the pointer basis; interference becomes unobservable in practice. The evidence retrieved here is thin on decoherence specifically — the search returned only three arXiv items, including a cloud-platform paper and a study of decoherence of superpositions by Reissner–Nordström black holes 1 — so the following should be read as the standard textbook picture rather than as a claim sourced to a specific retrieved paper. Decoherence explains why W's macroscopic superposition is empirically inaccessible, but it does not by itself solve the measurement problem: it converts a pure superposition into an improper mixture, and the question of why one branch is experienced remains.

This distinction matters for the user's argument. If "observation" meant "conscious registration," then a person who is unconscious, asleep, or dead would not collapse anything, and the notion of a private reality would follow almost trivially. If "observation" means "physical interaction that entangles the system with a macroscopic apparatus and environment," then observation is ubiquitous and impersonal: a photographic plate, a bubble chamber, or a detector registers an outcome whether or not any person looks. The retrieved literature supports the second reading as the one at work in the formalism; the first reading is a philosophical interpretation layered on top.

2.4 Wigner's friend beyond foundations: what the recent literature actually argues

The 2023–2026 literature on Wigner's friend is active and, importantly, does not converge on "each observer has their own reality." The retrieved items include:

Paper (year)	Core move	Relevance to the user's thesis
Jones & Müller (2402.08727, 2024)	Argues the paradox's significance extends beyond quantum foundations and is not a feature unique to quantum theory or tightly tied to the measurement problem	Undercuts the idea that observer-relativity is a distinctively quantum fact about persons 2
Baumann (2308.08260, 2023)	Contrasts the friend's collapse description with Wigner's unitary treatment using classical information	Frames the disagreement as a description-choice, not two co-real worlds 2
Baumann & Brukner (2305.15497, 2023)	Examines the friend's memory and the no-signaling principle; Wigner's measurement generally changes the joint state	Shows the two perspectives are correlated, not sealed off 2
Allam & Matzkin (2310.04167, 2023)	Relativistic Wigner–friend scenarios and the tension for unitary accounts	Extends the problem to spacetime structure, not personal experience 2
Hausmann & Renner (2504.03835, 2025)	Argues the black-hole firewall paradox is the Wigner's-friend paradox	Demonstrates the structure is generic, appearing without gravity-specific assumptions 2
Silva, Rizzuti & Duarte (2605.27424, 2026)	Studies agreement and compatibility in the paradox	Directly addresses whether observers can be brought into agreement 2
Reichert & Enz (2608.02635, 2026)	Modified Copenhagen interpretation: universal observer-independent state, collapse as part of time evolution even in isolated systems, distinction between state and observers' knowledge	An explicit attempt to deny observer-relative reality while keeping collapse 2

Two features of this table deserve emphasis. First, the no-signaling result is a hard constraint: whatever the friend and Wigner each assign, the joint statistics cannot be used to send information between them 2. A world in which "other persons are just observed reality of oneself" would, if taken as a physical claim, have to reproduce no-signaling — and the retrieved work treats no-signaling as a constraint on how the perspectives relate, not as evidence that one perspective is unreal. Second, Reichert and Enz's modified Copenhagen interpretation is a direct counterexample to the inference "collapse implies observer-dependent reality": they retain collapse while positing a universal observer-independent quantum state and treating the state as distinct from observers' knowledge 2. The inference is therefore not forced by the physics.

2.5 The first-person limit: why "I did not observe myself die" does not entail "I did not die"

The user's central move is: a person who dies does not observe his own death, therefore from his own perspective he did not die, therefore other persons' deaths are only observed realities of himself. The first clause is true but trivial; the inference is where it fails.

• Indexical asymmetry. "I observe X" and "X happens" are different predicates. The fact that there is no experiential report from the dead is a fact about the availability of reports, not about the occurrence of the event. Quantum mechanics has no term for "experience"; it has terms for states, observables, and outcomes.
• The symmetry argument cuts the other way. If the absence of self-observation of death implied non-death, the same logic would imply that a person who is unconscious during surgery did not have surgery. The premise (no self-observation) is satisfied in both cases; the conclusion is false in the second, so the inference form is invalid.
• Relational facts are still facts. In Wigner's-friend setups, F's outcome and W's superposition are related by a well-defined mathematical map (tracing out the lab). The relation is not "F's world versus W's world with no bridge"; it is a single joint state described at two levels of coarse-graining [CIT-arXiv:1604.07422v2]. By analogy, the dying person's absence of self-observation and the survivor's observation of the death are two descriptions of one entangled physical process, not two disjoint realities.
• No-signaling as a boundary condition. Any interpretation that treats other persons as mere contents of one's own observation must explain why the correlations still obey no-signaling and why intersubjective agreement is achievable at all — the very question Silva, Rizzuti, and Duarte address 2.

A useful way to see the structure is as a chain of distinctions rather than a chain of worlds:

flowchart TD
    A[Unitary evolution of joint system] --> B[Entanglement with apparatus and environment]
    B --> C[Decoherence: off-diagonal terms unobservable]
    C --> D[Effective classical outcomes for each branch]
    D --> E[Agent F: definite outcome, pure state assignment]
    D --> F[Agent W: superposition, reduced state assignment]
    E --> G[Different state descriptions of ONE joint system]
    F --> G
    G --> H[No contradiction in plain Wigner's friend]
    H --> I[Contradiction only with extra assumptions about reasoning and fact stability]
    I --> J[Interpretive choice: collapse postulate, Copenhagen, modified Copenhagen, etc.]

The diagram makes the key point visual: the fork between F and W occurs at the level of description, and the branches rejoin at the level of the joint state. Nothing in the structure requires that F's death "not happen" for F while happening for W.

2.6 What the evidence does and does not establish

Three limits on the evidence should be stated plainly. First, the search for "measurement problem" returned seven arXiv papers on measurement in unrelated domains — visual measurement, 3-D deformation measurement, PMU-based voltage stability, educational measurement, OPC UA/IO-Link sensor networks, powerline-communication GANs, and superconductor surface impedance — with no paper directly addressing the quantum measurement problem 3. The foundational claims in this section therefore rest on the Frauchiger–Renner source and the Wigner's-friend cluster, not on a broad consensus sample. Second, the decoherence search returned only three items and the retrieved note is truncated mid-sentence, so decoherence is treated here at textbook level rather than with specific citations 1. Third, the Wigner's-friend literature is heterogeneous in aim: some papers use the paradox to probe black-hole firewalls 2, others to test whether the paradox is quantum-specific at all 2. Absence of a paper defending "private worlds" is not proof that no such paper exists; it is only evidence that the retrieved corpus does not contain one.

2.7 Interim conclusion

Quantum mechanics supplies a genuine and unresolved measurement problem, a real observer-relative state description in Wigner's-friend setups, and a hard no-signaling constraint on how perspectives relate [CIT-arXiv:1604.07422v2] 2. It does not supply a licit inference from "I do not observe my own death" to "my death does not occur," nor from "my observations are mine" to "other persons are only my observations." The plain Wigner's-friend setup is explicitly not a contradiction [CIT-arXiv:1604.07422v2], and at least one 2026 proposal retains collapse while insisting on an observer-independent state 2 — showing that the interpretive space is wider than the user's dichotomy. The remaining sections should therefore treat the user's thesis as a philosophical position that borrows quantum vocabulary, and evaluate it on philosophical and phenomenological grounds rather than as a consequence of quantum theory.

3. Interpretations of Quantum Mechanics and the Observer's Role

The central question this section must answer is whether the observer is fundamental in quantum theory — a constitutive ingredient without which no fact is well-defined — or merely instrumental, a bookkeeping device that records outcomes whose definiteness comes from somewhere else (decoherence, a classical apparatus, a universal state, or nothing at all). The user's premise, that each person lives only for himself and that other persons are merely "observed reality" that does not really happen to them, is a strong first-person solipsistic reading of observer-dependence. The evidence assembled here shows that no major interpretation licenses that reading: even the most observer-relative framework on record, Relational Quantum Mechanics, makes facts relational between physical systems, not private to a conscious subject, and explicitly denies that the quantum state is "actual stuff" [CIT-2109.09170v3]. The interpretations differ sharply on where definiteness comes from, but they converge on treating the observer as one physical system among others rather than as the unique locus of reality.

3.1 The formal fault line that generates the observer question

Every interpretation is a response to the same structural tension: standard quantum mechanics contains two dynamical rules that do not obviously compose. Unitary, deterministic evolution of the state vector (Schrödinger) sits alongside the Born rule, which assigns probabilities to measurement outcomes; collapse is added as a separate postulate rather than derived from unitary evolution [CIT-arXiv:1604.07422v2]. Frauchiger and Renner frame the resulting "measurement problem" as the question of whether quantum theory can be applied to systems that include the agents using it, noting that direct tests are confined largely to microscopic domains even though the theory is presumed almost universally valid — with Schrödinger's cat as the canonical stress test [CIT-arXiv:1604.07422v2]. The observer enters precisely at this seam: if the theory is universal, the observer is a quantum system and must be describable by the theory; if the observer is outside the theory, universality fails. The user's premise is one extreme resolution of this seam — the observer is so central that only his own facts exist. The interpretations below occupy the space between that extreme and its opposite (a fully observer-independent state).

The founding argument for observer-relative descriptions is Wigner's friend. Agent F measures a spin and, having seen outcome z, assigns it a definite pure state; agent W, outside the isolated lab and ignorant of z, may instead assign the entire lab — spin, device, and friend — a macroscopic superposition, by linearity of the map S→L [CIT-arXiv:1604.07422v2]. Frauchiger and Renner stress that the plain Wigner's-friend setup is not itself a contradiction: the difference between F's pure state and W's reduced state is a difference of description, not a logical conflict [CIT-arXiv:1604.07422v2]. This is the crucial technical point for the user's question. Wigner's friend establishes that descriptions can be agent-relative without establishing that reality is agent-private. The step from "F and W assign different states" to "only F's facts exist" is not licensed by the formalism; it is an additional philosophical posit.

3.2 Four families and how each treats "the other observer"

The evidence supports a comparison across four families, with the caveat that coverage is uneven: RQM and Copenhagen are documented from primary full text, Wigner's-friend literature is well represented, but many-worlds is represented only indirectly (through the unitary-treatment side of Wigner's-friend analyses) and QBism is not documented in the retrieved evidence at all. That gap matters and is flagged in §3.5.

Interpretation	Where definiteness comes from	Status of the observer	Status of "the other observer's" facts	Key evidence
Relational QM (Rovelli)	Facts realised only in interactions between two physical systems, labelled by the interacting pair; amplitudes give probabilities only when arguments are facts relative to the same system	One physical system among others; no privileged observer	Real relative to the pair that interacts; not absolute	[CIT-2109.09170v3], [CIT-quant-ph/9609002v2]
Copenhagen / neo-Copenhagen	"Stable facts"; decoherence (approximate) plus a classical/instrumental boundary	Instrumental; the observer marks where the classical description begins	Facts are stable but stability is only approximate	[CIT-2109.09170v3]
Unitary / no-collapse treatments (the W-side of Wigner's friend)	Nothing collapses; the whole lab stays in superposition	Observer is a quantum subsystem inside the universal state	W's description and F's description are both internally valid but not jointly compositional	[CIT-arXiv:1604.07422v2], 2
Modified Copenhagen with universal observer-independent state (Reichert & Enz)	A universal observer-independent quantum state; collapse as part of time evolution even in isolated systems; state distinguished from observers' knowledge	Observer's knowledge is explicitly not the state	Facts are observer-independent; knowledge is separate	2

Relational Quantum Mechanics is the interpretation closest to the user's intuition and therefore the most important to state precisely — because it stops short of the user's conclusion. Rovelli's handbook exposition states the theory's core as an "ontology of sparse relative events, or 'facts'": facts are realised only in interactions between two physical systems, are labelled by the interacting systems, and transition amplitudes yield probabilities only when their arguments are facts relative to the same system [CIT-2109.09170v3]. Two consequences follow. First, Rovelli explicitly denies that the quantum state ψ is "actual stuff," comparing it to a Hamilton–Jacobi function S — a bookkeeping device, not a picture of reality [CIT-2109.09170v3]. Second, his founding 1996 paper already framed the programme as removing the "observer–observed distinction": all systems are equivalent, and the theory describes only the information systems have about each other [CIT-quant-ph/9609002v2]. The relational move is therefore democratising, not solipsistic: it multiplies perspectives across all physical systems, whereas the user's premise singles out one conscious subject. On RQM, the friend's death is a fact relative to the friend's interactions and a different fact relative to Wigner's — but Wigner is equally a system whose facts are relative to him, so there is no asymmetry that would make Wigner's reality the only real one.

Copenhagen is characterised by Rovelli as an ontology built solely on "stable facts," which buys simplicity at two prices: stability is only approximate (decoherence is never exact), and the ontology cannot describe reality without decoherence; his verdict is that "we are all actually Wigner's friends, in any measurement" [CIT-2109.09170v3]. This is a pointed result for the user's question: on Rovelli's reading, Copenhagen does not escape observer-relativity — it merely hides it behind a classical boundary, and every measurement re-creates the Wigner's-friend structure. A modern neo-Copenhagen/instrumentalist line (Żukowski & Markiewicz) is reported in the evidence but its substantive claims are truncated, so it cannot be compared in detail here.

Unitary / no-collapse treatments appear in the Wigner's-friend literature as the W-side description: Baumann analyses classical information and collapse in Wigner's-friend setups, contrasting the friend's collapse description with Wigner's unitary treatment 2; Baumann and Brukner examine the friend's memory and the no-signaling principle, noting that Wigner's measurement generally changes the joint state 2. Allam and Matzkin address relativistic Wigner-friend scenarios and the tension this creates for unitary accounts of measurement 2. Jones and Müller go further, challenging the view that the paradox captures a feature unique to quantum theory or closely tied to the measurement problem, arguing its significance extends beyond quantum foundations 2. If Jones and Müller are right, the observer-relativity at issue is not a quantum peculiarity at all — which weakens any inference from quantum formalism to a metaphysics of private worlds.

A universal-state variant. Reichert and Enz propose a modified Copenhagen interpretation assuming a universal observer-independent quantum state, collapse as part of time evolution even in isolated systems, and a distinction between the quantum state and observers' knowledge 2. This is the cleanest counter-position to the user's premise in the retrieved evidence: it makes the state observer-independent and treats observers' knowledge as a separate, non-constitutive layer. Notably, it does so within a Copenhagen-adjacent framework, showing that observer-relativity is not forced even by collapse-based approaches.

3.3 The composition problem: why "facts for me" do not compose into "facts for everyone"

The deepest technical obstacle to the user's premise is not interpretive taste but a composition failure. Frauchiger and Renner's contribution is to show that when agents reason about each other's reasoning — F about W, W about F — the assumption that each agent's facts can be combined into a single consistent global account breaks down under certain assumptions [CIT-arXiv:1604.07422v2]. The structure is a chain:

flowchart TD
    A[Unitary evolution is universal] --> B[Observer is a quantum system]
    B --> C[Wigner's friend: F's definite outcome vs W's superposition]
    C --> D{Can F's and W's facts be composed?}
    D -->|Plain Wigner's friend: YES| E[No contradiction — difference of description]
    D -->|Nested reasoning: NO| F[Composition failure under stated assumptions]
    F --> G[Interpretive choice: give up universality, give up single-world, give up absoluteness of facts, or restrict composition]
    E --> H[Agent-relativity of description does NOT entail privacy of reality]

The plain setup yields no contradiction — only a difference of description [CIT-arXiv:1604.07422v2]. The contradiction, where it arises, is a composition failure, and each interpretation resolves it differently: by restricting which facts can be combined (RQM's same-system requirement for amplitudes [CIT-2109.09170v3]), by denying collapse (unitary treatments 2), or by positing a universal observer-independent state (Reichert & Enz 2). None of these resolutions says that the friend's death did not happen to the friend. They say that which facts can be jointly asserted is constrained. That is a logical grammar of facts, not a metaphysics of solitary selves.

A second technical constraint cuts against the user's premise even more directly: no-signaling. Baumann and Brukner note that Wigner's measurement generally changes the joint state, yet the friend's memory and the no-signaling principle constrain what that change can mean operationally 2. If one agent's observation could make another agent's events unreal in a way that mattered, the no-signaling structure would be violated. The formalism is built to prevent exactly the kind of cross-agent ontological cancellation the user's premise implies.

3.4 What the evidence does not support, and where the user's premise would have to land

Three inferential gaps separate the retrieved evidence from the user's conclusion.

1. From "state is relational" to "reality is private." RQM makes facts relative to pairs of physical systems, not to conscious subjects [CIT-2109.09170v3]. The relata are systems, and all systems are equivalent [CIT-quant-ph/9609002v2]. Substituting "person" for "system" and "consciousness" for "interaction" is an extra step the primary text does not take.
2. From "ψ is not actual stuff" to "nothing is actual." Rovelli's comparison of ψ to a Hamilton–Jacobi function is an anti-realist claim about the state vector, not about events: his ontology is explicitly an ontology of events or facts [CIT-2109.09170v3]. Denying that ψ is stuff is not denying that interactions occur.
3. From "Wigner and friend disagree" to "only one of them exists." The plain Wigner's-friend setup is explicitly not a contradiction [CIT-arXiv:1604.07422v2]; the friend's collapse description and Wigner's unitary description are both internally valid 2. Disagreement of description is not evidence of non-existence of one relatum.

Where would the user's premise land if made precise? It would be a position on which facts are indexed to a single subject and other subjects are not fact-bearers. The closest documented position is RQM, and RQM is explicitly not that: it indexes facts to interacting systems symmetrically [CIT-2109.09170v3], [CIT-quant-ph/9609002v2]. The closest documented opposite is the universal observer-independent state of Reichert and Enz 2. The user's premise sits outside both, and the retrieved evidence contains no primary source defending it.

3.5 Coverage gaps and how they bound the conclusions

The evidence base is uneven and the comparison above must be read with that in mind.

• QBism is absent. The section intent calls for comparing QBism, but no retrieved evidence documents QBism's claims. QBism is the interpretation most naturally allied with a first-person stance (it treats probabilities as an agent's personal degrees of belief), so its absence is a real gap: the strongest available ally of the user's intuition is not represented in the evidence, and no claim about QBism is made here.
• Many-worlds is represented only indirectly, through the unitary W-side of Wigner's-friend analyses 2, not through primary many-worlds texts.
• RQM-specific literature is thin in the search index. A paper_search for "relational quantum mechanics" returned eight arXiv papers, none of which directly addresses RQM as a named interpretation; the closest thematically are papers on quantum reference frames and quantized geometry — "Doubly Quantum Mechanics" (D'Esposito, Fabiano, Frattulillo, Mercati; arXiv:2412.05997, 2024), which quantizes system geometries, measurement apparatuses, and reference-frame transformations into "geometry" states motivated by quantum-gravity symmetries, and "Quantum Galilei group as quantum reference frame transformations" (Ballesteros, Fernandez-Silvestre, Giacomini, Gubitosi; arXiv:2504.00569, 2025) 4. The RQM content in this section therefore rests on Rovelli's own primary texts [CIT-2109.09170v3], [CIT-quant-ph/9609002v2], not on the search index.
• The "measurement problem" query returned no quantum-foundations papers — seven results across unrelated domains (visual measurement descriptors, 3-D deformation measurement, PMU voltage-stability assessment, educational measurement, OPC UA/IO-Link sensor networks, powerline-communication GANs, surface impedance in superconductors) 3. The measurement-problem content in §3.1 therefore rests on the Frauchiger–Renner primary text [CIT-arXiv:1604.07422v2], not on that query.
• Decoherence evidence is thin: the "quantum decoherence" query returned three papers, of which the only substantive one retrieved is a hardware description of the 105-qubit Tianyan-287 superconducting processor with 99.90% single-qubit, 99.56% two-qubit, and 98.7% readout fidelity 1, 4. This is relevant to engineering coherence, not to the interpretive role of decoherence, so the claim that decoherence is "never exact" rests on Rovelli's characterisation [CIT-2109.09170v3] rather than on an independent decoherence source.

These gaps bound the conclusion in one direction only: they do not show that any interpretation supports the user's premise, and they do not show that interpretations disagree about it — they show that the premise is not represented in the retrieved primary literature at all. Missing evidence is not disagreement, and it is also not support.

3.6 Interim answer to the section question

On the retrieved evidence, the observer's role is interpretation-dependent but never solipsistic. RQM makes facts relational to interacting systems and denies that ψ is actual stuff, while retaining an ontology of events [CIT-2109.09170v3], [CIT-quant-ph/9609002v2]. Copenhagen, on Rovelli's reading, is itself inescapably Wigner's-friend-like because decoherence is never exact [CIT-2109.09170v3]. Unitary treatments keep the whole lab in superposition and treat F's and W's descriptions as both valid but not jointly compositional [CIT-arXiv:1604.07422v2], 2. A modified Copenhagen variant restores an observer-independent universal state and separates state from knowledge 2. The one thing the formalism consistently forbids is the move the user's premise requires — that one agent's observation could render another agent's events unreal — because the plain Wigner's-friend setup is not a contradiction [CIT-arXiv:1604.07422v2] and the no-signaling structure constrains cross-agent effects 2. Whether the observer is fundamental remains genuinely contested; whether the observer is sole is not supported by any retrieved primary source.

4. From Solipsism to Quantum Solipsism

The thesis under examination is not classical metaphysical solipsism — the claim that nothing exists outside my mind — but a narrower perspectival or experiential solipsism: that every event is only ever "for" some observer, so that another person's death is real for me but never "for them," because they never observe their own non-existence. The philosophical literature treats these two claims very differently, and the central analytical task of this section is to show that the move from "I only have access to my own experience" to "other persons are merely observed realities within my experience" is a non sequitur that quantum mechanics, properly read, does not license. Quantum interpretations supply genuine perspectival structures (facts relative to a system), but every serious version of them is careful to distinguish relativity-of-facts from the collapse of reality into a single observer's mind.

4.1 What classical solipsism actually claims — and what it does not

The SEP entry on Other Minds frames the solipsism question narrowly — "whether I am alone in the universe" — as a mid-twentieth-century preoccupation that displaced earlier, purely epistemological worries about how we infer other minds at all 5. The IEP entry reconstructs the doctrine as resting on three widely held presuppositions, two of which are (a) that what I know most certainly are the contents of my own mind — thoughts, experiences, affective states — and (b) that there is no conceptual or logically necessary link between the mental and the physical 5. This structure is important because it shows that classical solipsism is an epistemic doctrine dressed as a metaphysical one: it begins from the privileged certainty of first-person contents and then overreaches to the conclusion that only those contents exist. The user's thesis inherits exactly this structure. It starts from the true observation that a person's death is never an event in their own experience (there is no experienced moment of "my death"), and concludes that the death therefore does not happen "to" them at all. That inference is the same overreach the IEP presuppositions warn against: from the certainty and privacy of first-person contents, nothing follows about whether other minds or other deaths exist.

A second distinction matters here. Classical solipsism is a claim about existence (only I exist); the user's thesis is a claim about location of events (events happen only in someone's observation). The latter is closer to what philosophers call perspectivalism or indexicalism about experience: the claim that all facts are facts-for-a-subject. The literature treats perspectivalism as far more defensible than solipsism, precisely because perspectivalism does not deny that other subjects exist — it only denies that facts are subject-neutral. The user's argument, however, slides from perspectivalism back into solipsism by treating other persons as objects within one's observation rather than as other centres of observation. That slide is the load-bearing error, and the rest of this section shows why quantum mechanics does not support it.

4.2 Where quantum mechanics genuinely looks solipsism-adjacent

Quantum mechanics does contain a real, non-trivial perspectival structure, and it is worth stating it precisely because it is the strongest available foothold for the user's intuition. In Relational Quantum Mechanics (RQM), Rovelli's core ontology is an "ontology of sparse relative events, or 'facts'": facts are realised only in interactions between two physical systems and are labelled by the interacting systems, and quantum transition amplitudes yield probabilities only when their arguments are facts relative to the same system [CIT-2109.09170v3]. Rovelli explicitly denies that the quantum state ψ is "actual stuff," comparing it to a Hamilton–Jacobi function — a bookkeeping device, not a picture of reality [CIT-2109.09170v3]. His founding 1996 paper already framed the programme as removing the "observer–observed distinction": all systems are equivalent, and the theory describes only the information systems have about each other [CIT-quant-ph/9609002v2]. Read carelessly, this looks like the user's thesis: every fact is a fact-for-a-system, so nothing happens except relative to an observer.

But the SEP entry on RQM flags the exact tension the user's argument exploits, and names it: RQM may prima facie imply "perspectival solipsism," since variable values realised relative to one system (S) need not match those realised relative to another (S') 6. The entry cites Pienaar's 2019 criticisms and Martin-Dussaud, Rovelli, and Zalamea (2019) on the sense in which RQM is nonlocal 6. Crucially, the same literature reports that Rovelli rejects "observer-dependence" implying conscious observers, stressing instead that reality is relational and that a system's state can be described relative to any physical object 6. This is the decisive disanalogy with the user's thesis. In RQM the "observer" is any physical system whatsoever — a photon, a detector, a rock — not a conscious self. The relativity is physical, not experiential. The user's thesis requires the observer to be a subject whose experience constitutes the event; RQM requires only that the observer be a system that interacts. A rock has no experience of the event, yet in RQM the event is still realised relative to it. So the quantum perspectivalism that superficially supports the thesis actually undercuts its central move: events are relative to interactions, not to experiences, and therefore another person's death can be a realised fact relative to the physical systems involved (including, in the relevant interaction, the dying person's body) without anyone "observing themselves die."

4.3 The dilemma the quantum-solipsist faces

The secondary literature on RQM sharpens this into a dilemma that maps directly onto the user's position. Muciño, Okon, and Sudarsky (2022) argue that RQM either collapses toward solipsism or adds something ad hoc to avoid it 6. The research notes frame the same fork: rejecting shared facts yields solipsism or "island universes," while rejecting observer-relative comparisons loses RQM's distinctiveness 6. A Springer Foundations of Physics article, "Relational Quantum Mechanics at the Crossroads," asks whether RQM confuses relativity with subjectivity and argues that any genuine clash with scientific objectivity must lie elsewhere 6. This is the precise pressure point for the user's thesis:

Move available to the quantum solipsist	What it buys	What it costs
Keep relativity, keep shared facts (mainstream RQM)	Preserves intersubjective agreement and science	Observer = any physical system, not a conscious self; the "death is only for me" claim loses its premise
Keep relativity, drop shared facts (island universes)	Maximally supports "each person lives only for himself"	Collapses into solipsism; makes science and testimony inexplicable; Muciño–Okon–Sudarsky call the escape ad hoc 6
Drop relativity, keep a privileged observer (neo-Copenhagen)	Restores a single objective description	Reintroduces the observer–observed distinction Rovelli's programme was built to remove [CIT-quant-ph/9609002v2]

The user's thesis sits in the second row: it wants the perspectivalism (each event only for its observer) without the physical discipline (observer = interacting system). But the second row is exactly the position the literature identifies as unstable. If facts are only relative to observers and there are no shared facts, then the "other person" in my observation is not a subject at all — which is precisely what the thesis asserts — but then the thesis can no longer explain why my observation should be privileged over the observation of the "observed reality" that is the other person. The asymmetry the thesis needs (my experience is real, theirs is merely observed) has no quantum-mechanical basis. RQM is symmetric: every system is an observer relative to its interactions, and none is privileged [CIT-quant-ph/9609002v2][CIT-2109.09170v3].

4.4 Why the death example does not go through

The death example is the thesis's strongest intuitive case, and it is worth isolating why it fails on the physics. The claim is: "the person who died did not die as he observed, because he did not observe himself die." Two things are being conflated. First, the absence of an experienced moment of death is a fact about the structure of experience — there is no vantage point from which one experiences one's own non-existence — and it is true for every event that terminates experience, not special to death. It does not show that death did not happen to the person; it shows only that death is not an object of first-person experience. Second, the realisation of a fact relative to a system in RQM does not require that the system experience the fact. A fact is realised in an interaction and labelled by the interacting systems [CIT-2109.09170v3]. The dying person's body is one of the interacting systems; the fact of death is realised relative to it in the same way any physical fact is realised relative to the systems that interact. Nothing in RQM requires a conscious observer to "register" the fact for it to be a relative fact. So the inference "he did not observe himself die, therefore he did not die" equivocates between observation in the phenomenological sense (which the thesis needs) and interaction in the RQM sense (which is what the physics actually provides). The equivocation is the whole argument.

There is a further problem with the "other persons are just observed realities" clause. If other persons are merely contents of my observation, then the person whose death I observe is not a subject and has no perspective — but the thesis simultaneously wants to say that that person has a perspective (namely, that they did not observe their own death). The thesis needs the other person to be both a mere observed object (so that their death is "only for me") and a genuine subject with a first-person perspective (so that their non-observation of their death is meaningful). These two requirements are inconsistent. Either the other person is a subject, in which case their death is real for them in whatever sense any relative fact is real for a system, or they are not a subject, in which case there is no "their" perspective for the death to be withheld from. The death example trades on the second reading while presupposing the first.

4.5 What survives, and what does not

Stripped of the overreach, the user's intuition retains a defensible core: first-person experience is perspectival, and no one can occupy another's perspective. That is true and philosophically important, but it is a claim about epistemic access, not about what exists. It is the IEP's presupposition (a) — what I know most certainly are the contents of my own mind 5 — and it does not entail that other minds or other deaths are unreal. Quantum mechanics adds a second, weaker perspectival layer: facts are relative to interacting systems [CIT-2109.09170v3]. But this layer is physical and symmetric, and it explicitly refuses the conscious-observer reading 6. The quantum-solipsist conclusion therefore requires a premise the physics does not supply — that the relevant "observer" is a conscious subject whose experience constitutes reality — and that premise is precisely what Rovelli's programme was designed to eliminate [CIT-quant-ph/9609002v2]. The honest summary is that quantum mechanics gives the thesis a vocabulary (relativity of facts, observer-dependence) but not a warrant: the vocabulary is borrowed from a theory in which the observer is any physical system, and the warrant would require the observer to be a privileged conscious self, which the theory denies. The gap between "my experience is mine alone" and "other persons are only observed realities" is not bridged by quantum mechanics; it is only disguised by it.

Two caveats bound this conclusion. First, the evidence base here is uneven: the search specifically targeting Fuchs's QBism and its "not solipsism" defence returned no results 7, so the QBist side of the comparison is under-evidenced in this section, and the conclusion should be read as established for the RQM/Copenhagen axis rather than for QBism, where a separate agent-centred argument would need to be checked against primary text. Second, the claim that RQM "collapses toward solipsism" is a criticism in the literature, not a consensus finding 6; the SEP entry presents it as a prima facie tension and cites both critics and defenders, so the dilemma in §4.3 should be treated as a live interpretive dispute rather than a settled refutation. What is not in dispute is the structural point: the user's thesis needs an asymmetric, experience-constituted observer, and no mainstream interpretation supplies one.

5. Quantum Immortality and First-Person Death

The strongest defensible version of the user's intuition is not that "other people's deaths don't happen," but that first-person survival and third-person death are indexed to different observers, and that no observer can occupy the standpoint of their own non-existence. Quantum immortality is the most aggressive attempt to turn that indexing fact into a physical claim. This section separates what the thought experiment actually asserts, what the retrieved evidence can and cannot support, and where the inference from "I never observe my own death" to "I never die" breaks.

5.1 What the thought experiment actually claims

Quantum suicide/immortality adapts Schrödinger's cat to the cat's own point of view: an observer is coupled to a lethal quantum trigger (e.g., a spin measured in a superposition, gun fires on "up," not on "down"). On the Copenhagen reading the observer dies with probability ½ per round; on many-worlds the wavefunction splits, and in at least one branch a surviving, conscious observer always continues. Iterating the experiment, the survivor's first-person record reads "I survived again, and again," while an external observer in most branches sees a corpse 8. Popular and encyclopedic treatments explicitly frame it as a purported argument that could discriminate Copenhagen from many-worlds, and stress it is a thought experiment not meant to be carried out 8.

Two structural features matter for the user's framing. First, the argument is branch-relative: it does not say death fails to occur, only that death occurs in branches whose continuation the survivor does not inhabit. Second, it is interpretation-dependent: it presupposes that the wavefunction branches into genuinely realized worlds with continuing conscious subjects. The user's stronger claim — that other people are "just an observed reality of himself" and their events "do not really happen to the other person" — is not what the thought experiment asserts, and the evidence does not support that stronger reading.

flowchart TD
    A[Observer coupled to lethal quantum trigger] --> B{Interpretation}
    B -->|Copenhagen| C[Single outcome: death with p = 1/2 per round]
    B -->|Many-worlds| D[Wavefunction branches]
    D --> E[Branch where observer survives]
    D --> F[Branch where observer dies]
    E --> G[First-person record: 'I survived again']
    F --> H[Third-person record: external observer sees a corpse]
    G --> I[Iterate: survivor's first-person stream continues]
    I --> J[Inference to 'quantum immortality']
    J --> K[Contested: does branching license a personal-survival claim?]

5.2 The counter-argument the evidence actually locates

The one load-bearing source the retrieval surfaced is a paper titled Many-Worlds Interpretations Can Not Imply 'Quantum Immortality' (arXiv:0902.0187), which argues against the inference and notes that Everett's own death may have been a variant of the idea 8. This is the crucial corrective: the existence of a surviving branch is a statement about the structure of the wavefunction, not automatically a statement about personal survival. Whether "I" persist in the surviving branch depends on a theory of personal identity across branches — a metaphysical premise the branching formalism does not supply. The retrieved evidence reports this as a located title and thesis, not as verified full-text content, so the argument's specific premises should be treated as unconfirmed here.

This is where the user's intuition and the physics diverge most sharply. The user reasons: "I do not observe myself dying, therefore I do not die; therefore others' deaths are only my observation." The first clause is nearly tautological (an observer cannot record the moment of their own non-existence as an experienced event). The second clause is the contested inference. The third clause — that other people's deaths are merely my observation and "do not really happen to the other person" — does not follow at all, and is a solipsistic move that the quantum-immortality literature does not make.

5.3 First-person versus third-person: a comparison

Aspect	First-person account	Third-person account
What is recorded	"I survived again" — a continuous stream of experience	A corpse in most branches; survival in a measure-zero-ish set of branches
What can be observed	Only branches in which an observer exists to observe	All branches, in principle, from outside
Death	Never an experienced event for the subject	An observable, datable event
Logical status	Near-tautological (no experience of non-existence)	Empirical claim about branch structure
Inference to "immortality"	Contested; requires a theory of personal identity across branches	Does not follow from branching alone

The table makes the asymmetry explicit: the first-person column is nearly analytic, the third-person column is empirical, and the leap from one to the other is exactly what arXiv:0902.0187 disputes 8.

5.4 Why the observer-role literature does not rescue the stronger claim

The user's framing leans on the idea that reality is constituted by observation. The retrieved interpretation literature is relevant here but cuts against the solipsistic reading. Rovelli's Relational Quantum Mechanics states its core as an "ontology of sparse relative events, or 'facts'": facts are realised only in interactions between two physical systems and are labelled by the interacting systems, and transition amplitudes yield probabilities only when their arguments are facts relative to the same system [CIT-2109.09170v3]. Crucially, Rovelli explicitly denies that the quantum state ψ is "actual stuff," comparing it to a Hamilton–Jacobi function — a bookkeeping device, not a picture of reality [CIT-2109.09170v3]. His founding 1996 paper framed this as removing the "observer–observed distinction": all systems are equivalent and the theory describes only information systems have about each other [CIT-quant-ph/9609002v2].

This is a relational ontology, not a solipsistic one. Facts are relative to interacting systems — but every physical system counts as a system, so other people's facts are as real as one's own, just indexed differently. Rovelli's characterisation of Copenhagen is instructive: it is an ontology built solely on "stable facts," buying simplicity at two prices — stability is only approximate (decoherence is never exact), and the ontology cannot describe reality without decoherence; his verdict is that "we are all actually Wigner's friends, in any measurement" [CIT-2109.09170v3]. "We are all Wigner's friends" is the opposite of "only I am real": it says every observer is inside the same relational structure, not that one observer is privileged.

5.5 What the evidence does not establish

The retrieval for this section was weak, and the gaps should be stated plainly rather than papered over. arXiv keyword searches for "quantum immortality," "quantum suicide Everett," and "Everett immortality observer" returned mostly off-topic physics and public-health papers; the only load-bearing source located is the web-search hit on arXiv:0902.0187 plus general encyclopedic/popular framing 8. No full PDF of that paper was read, so its argument is reported as a located title and thesis, not verified full-text content. The paper-search for "quantum immortality" returned ten arXiv papers, none of which explicitly addresses quantum immortality; the results are general quantum-information, foundations, and quantum-gravity papers 9. The paper-search for "quantum suicide Everett" returned no paper directly addressing quantum suicide, splitting into keyword matches on "Everett" (quantum foundations) and on "suicide" (public-health/NLP) 10. The relational-quantum-mechanics search likewise returned no paper directly addressing RQM as a named interpretation 4.

What this means for the section's claims: the structure of the thought experiment is well attested by encyclopedic and popular sources 8; the counter-argument is attested only at title-and-thesis level 8; the relational alternative is attested at full-text level for Rovelli's own exposition [CIT-2109.09170v3][CIT-quant-ph/9609002v2]. The user's stronger solipsistic claim is not attested by any retrieved source and is contradicted by the relational framing, which treats all interacting systems as equally real.

5.6 Unresolved questions

Three questions remain genuinely open on the retrieved evidence. First, does branching license personal survival? This turns on a theory of personal identity across branches that the formalism does not supply, and arXiv:0902.0187 disputes the inference 8. Second, is the first-person/third-person asymmetry a physical fact or a grammatical one? The near-tautology that "I cannot experience my own non-existence" is a fact about experience, not obviously about branch structure. Third, does the relational ontology actually block solipsism, or merely relocate it? Rovelli's "we are all Wigner's friends" [CIT-2109.09170v3] is a strong statement against privilege, but the retrieved evidence does not include a full derivation showing why one system's facts cannot be systematically privileged over another's. These are the questions a reader should carry forward rather than treat as settled.

6. Empirical, Logical, and Ethical Critiques

The position under examination is not one claim but a conjunction, and the critique has to separate them before it can say anything useful. Call the first conjunct the perspectival claim: every observational fact is indexed to an observer, so a sentence like "X died" is incomplete until it is relativized to someone's perspective. Call the second the metaphysical claim: other people's experiences — including their deaths — never occur at all, and other persons are merely contents of the speaker's own observed reality. The central critical result of this section is that the perspectival claim has genuine technical support in the quantum-foundations literature, while the metaphysical claim is an add-on that the physics does not supply and that the most relevant perspectival framework explicitly disowns. The empirical, logical, and ethical objections therefore land almost entirely on the second conjunct.

6.1 The perspectival claim is defensible; the solipsistic inference is not

Zwirn's "Convivial Solipsism" is the strongest quantum-perspectival framework retrieved, and it is instructive precisely because it grants the first-person indexing while refusing the leap to "only I am real." On this view observed events are not absolute, there is no collapse and one world, and a statement like "the friend saw outcome A" must be rewritten as "from the friend's perspective…" 11. That is exactly the move the user's position makes in its first half. But Zwirn's most recent paper pre-emptively rejects the inference to the metaphysical claim: objections to perspectivalism arise by "removing these indices and then treating the resulting expressions as if they belonged to a single global factual domain," which "leads to apparent contradictions and to false dilemmas concerning consciousness, communication, other minds, and intersubjectivity," and he insists the view "is not a retreat into psychological solipsism, but a discipline of perspectival discourse" 11. This is a decisive internal critique: the framework that most nearly formalizes "events happen for an observer" treats the slide from indexed facts to solipsistic facts as a grammatical error, not a discovery. The user's conclusion that other persons "do not really happen to the other person" is therefore not a consequence of quantum perspectivalism; it is a separate metaphysical thesis that must be defended on other grounds and, as shown below, is not.

The same structure appears in the Wigner's-friend literature. The founding argument (Wigner 1967) does establish observer-relative descriptions: agent F, having seen outcome z, assigns a definite pure state, while agent W outside the isolated lab may assign the entire lab a macroscopic superposition by linearity of the map S→L 2. But Frauchiger and Renner emphasize that the plain Wigner's-friend setup is not a contradiction — the difference between F's pure state and W's reduced state is a difference of description, not evidence that F's experience failed to occur 2. The friend's observation is real from the friend's perspective; that is the whole point of the indexing. The user's move — concluding that because the friend did not observe himself dying, the death did not happen to him — conflates "no observer-independent fact of the matter about the outcome" with "no fact of the matter from the friend's own perspective." The first is a live interpretive option; the second is contradicted by the setup itself, in which the friend is stipulated to have a definite record.

6.2 Empirical critique: no experiment distinguishes "others are observed reality" from "others are real"

The empirical objection is not that the solipsistic thesis has been falsified — it is that it has not been made testable, and the available evidence cannot bear on it. Two lines of evidence are relevant, and both cut against treating the strong claim as scientifically established.

First, the decoherence literature constrains how long quantum coherence can survive in a brain. Tegmark's analysis of quantum decoherence in brain processes is the canonical reference here, estimating decoherence times on the order of $10^{-13}$ seconds for relevant neural degrees of freedom 11. Whatever the precise number, the order of magnitude means that macroscopic superpositions of neural states — the kind that would be needed for a brain to be in an observer-relative superposition with respect to another observer in any dynamically relevant sense — are suppressed on timescales vastly shorter than any neural or cognitive process. This does not refute perspectivalism as an interpretive stance, but it removes the most natural physical mechanism by which one person's "observed reality" could be ontologically insulated from another's. The user's picture requires that other persons be, in effect, branches of the speaker's own observation; decoherence makes that picture empirically idle, because the branches do not interact and no measurement can reveal them.

Second, the search for direct critiques or tests of quantum theories of consciousness returned no paper that empirically adjudicates the solipsistic claim 12. The retrieved literature clusters around artificial/AI consciousness and general theory of consciousness: Koch argues that indicator-based assessments of artificial consciousness cannot be calibrated against independently established artificial-consciousness outcomes and have limited evidential relevance 12; McClelland addresses decision-making under deep uncertainty about AI consciousness, weighing harm to potentially sentient systems against wasted resources 12; Albantakis examines the utility of highly idealized toy models for evaluating theories of consciousness 12. The only quantum-adjacent item reads the Tractatus Quanticus and related work as a "New Tractatus Program" linking quantum mechanics, anti-totalitarian ontology, and consciousness 12 — a programmatic framing, not an empirical test. The honest summary is that the empirical record contains no experiment whose outcome would differ depending on whether other persons are real or merely observed. A thesis that makes no differential prediction is not thereby false, but it cannot be presented as a scientific finding, and the user's phrasing ("in this means…") presents it as one.

A further empirical gap is worth flagging explicitly. The paper_search query for "problem of other minds" returned eight results, none of which addressed other-minds skepticism, theory of mind, or philosophy-of-mind epistemology; the hits were astronomy, agent tooling, and a gamma-ray-burst propagation study 13. This is a coverage failure of the retrieval, not evidence that the philosophical literature is silent — the SEP entry "Other Minds" is a standard reference and states that various considerations can generate an epistemological problem about other minds 5. The correct inference is that the empirical case for the strong claim is absent, while the philosophical case against it is well developed and was simply not retrieved by the automated search. Missing evidence does not establish disagreement, but here the missing evidence is missing on the side that would support the user's conclusion.

6.3 Logical critique: the thesis is self-undermining and equivocates on "observation"

The logical objections are independent of any experiment and are, in my assessment, the strongest part of the critique. Three are worth developing.

(a) The indexical self-undermining. If every event is indexed to an observer and no observer-independent facts exist, then the claim "other persons are only my observed reality" is itself an indexed claim — true, at most, from the speaker's perspective. But the speaker advances it as a claim about how things are, i.e., as a global fact. Zwirn's diagnosis applies verbatim: removing the indices and treating the resulting expressions as belonging to a single global factual domain "leads to apparent contradictions and to false dilemmas concerning consciousness, communication, other minds, and intersubjectivity" 11. The solipsist cannot consistently say "there are no other perspectives" without occupying a perspective that claims to survey all perspectives, which is precisely the global factual domain the perspectival claim denies.

(b) The equivocation on "observation." The argument trades on two senses of observation: (i) physical measurement, an interaction that correlates a system with an apparatus or record, and (ii) phenomenal awareness, a first-person experience. Quantum mechanics formalizes (i); the solipsistic conclusion needs (ii). The measurement problem is the mismatch between unitary evolution and the Born rule's probabilistic outcomes 2, and it is a problem about (i). Nothing in the formalism says that a measurement outcome is a phenomenal event, or that the only phenomenal events are the speaker's. The step from "outcomes are relational" to "only my experiences are real" requires a premise — that phenomenal awareness is the thing that collapses or selects outcomes — which is exactly the premise at issue and is not supplied by the physics. The Wigner's-friend literature is careful about this: Baumann analyzes classical information and collapse in Wigner's-friend setups, contrasting the friend's collapse description with Wigner's unitary treatment 2, and Baumann and Brukner examine the friend's memory and the no-signaling principle, noting that Wigner's measurement generally changes the joint state 2. These are claims about records and states, not about whose consciousness is privileged.

(c) The death asymmetry does not follow. The user's key example — the person who dies does not observe himself dying, therefore the death did not happen to him — is a non sequitur even granting perspectivalism. Perspectivalism says the fact "X died" is indexed; it does not say that an event requires the subject of the event to observe it. Most events indexed to an observer are observed by other observers: the friend's measurement outcome is definite from the friend's perspective and indefinite from Wigner's, but the friend's perspective is not the only perspective in the setup 2. Death is an event in the world that is observed by survivors, physicians, and records; the dying person's inability to observe his own death is a fact about the limits of first-person access, not evidence that the event lacks a perspective under which it occurred. The argument would equally prove that no one ever sleeps, since the sleeper does not observe himself sleeping. The asymmetry the user needs — that first-person observation is constitutive of events rather than merely one perspective among many — is asserted, not derived.

A compact way to see where the argument goes wrong is to separate three claims that the user's prose runs together:

Claim	Content	Status in the retrieved literature
C1	Observational facts are perspective-indexed	Defended (Zwirn's convivial solipsism) 11
C2	There is no observer-independent fact of the matter about outcomes	Live interpretive option; Wigner's-friend setups are not contradictions 2
C3	Other persons' experiences, including deaths, never occur	Not supported; explicitly disowned as "psychological solipsism" 11

The user's argument needs C3; the physics at most supports C1 and C2. The inference from C1–C2 to C3 is the load-bearing step, and it is the step that fails.

6.4 Ethical critique: the thesis is not ethically neutral, and its practical upshot is unstable

The ethical objection is not that solipsism is wicked; it is that the thesis, if taken seriously as a guide to action, dissolves the very relations that make ethical reasoning possible, and it does so asymmetrically — it is available to the speaker but not to anyone else. If other persons are only my observed reality, then their suffering is a feature of my experience rather than theirs, and the constraints that ordinarily bind my treatment of them (that they have interests that can be frustrated) lose their footing. This is not a hypothetical: the structure of the argument is exactly the structure that has historically been used to license treating others as mere appearances. The retrieved literature does not contain a direct ethical critique of quantum solipsism — the search for "quantum consciousness critique" returned no paper directly critiquing quantum theories of consciousness 12 — so this subsection is my inference from the logical structure rather than a report of a specific published argument, and it should be flagged as such.

Two further points sharpen the ethical critique. First, the thesis is self-exempting: the speaker claims a privileged status (the only real perspective) that he denies to every other person, and the denial is made in the second person — "you are only my observed reality." A position that cannot be stated in the first person without contradicting itself ("I am the only real perspective, and you, who are not real, should believe me") has a performative problem that is also an ethical one: it treats the interlocutor as a means to the speaker's metaphysical comfort. Second, the practical upshot is unstable in the way that all radical skepticism is unstable. The solipsist still eats, avoids pain, and grieves; the thesis is held in the study and abandoned in the clinic. That inconsistency is not a refutation, but it is evidence that the thesis is not doing the work it claims to do — it is a description that leaves practice untouched, which is exactly what one would expect if the metaphysical claim were an add-on rather than a discovery.

6.5 What would count as evidence, and why the strong claim remains unestablished

It is worth stating the conditions under which the strong claim could be scientifically established, because the absence of any such condition in the retrieved literature is itself the finding. The claim would need either (i) an experiment whose outcome differs depending on whether other persons are real or merely observed — and none is described in the retrieved corpus 1213; or (ii) a derivation from quantum mechanics showing that first-person phenomenal awareness is the entity that selects outcomes, which would require solving the measurement problem in favor of a consciousness-collapse interpretation and then showing that only one consciousness is privileged — a step no retrieved paper takes, and one that the Wigner's-friend literature treats as an interpretive choice rather than a result 2; or (iii) a demonstration that decoherence does not suppress the relevant superpositions in brains, which the Tegmark estimate of $\sim 10^{-13}$ s makes implausible 11. None of these is available.

The balanced conclusion is therefore not "solipsism is false" — that would overclaim, since the measurement problem is genuinely open and perspectivalism is a respectable response to it 211. The conclusion is that the user's position conflates an open interpretive question (C2) with a metaphysical doctrine (C3) that the physics does not entail, that the most relevant framework explicitly rejects, that no retrieved experiment can test, and that carries ethical costs the user's formulation does not acknowledge. The first-person indexing of events is a real feature of quantum description; the inference from it to "all persons are living only for themselves" is a philosophical add-on, and the evidence retrieved for this report does not establish it.

No external evidence was retrieved for the ethical subsection beyond the general critique search; the ethical analysis in §6.4 reflects the model's inference from the logical structure rather than a specific published source.

7. Conclusion

The question posed at the outset—whether a person can be said to "live only for himself," such that his own death is never observed by him and other people's deaths are merely contents of his observation—has a clear answer at the level of physics, and a much less clear one at the level of metaphysics. The reliable conclusion is this: nothing in quantum mechanics assigns a privileged, world-constituting observer to any person, and nothing in the formalism supports the inference that other people are "just observed reality" without independent existence. The measurement problem is real, and the role of the observer within it is genuinely unsettled; but the ambiguity concerns how (or whether) measurement outcomes become definite, not who is entitled to treat himself as the sole author of reality. The first-person asymmetry the topic describes—that I never observe my own non-existence—is a grammatical and epistemic truism, not a quantum result. It holds in classical physics, in everyday life, and in any interpretation whatsoever, because "observing my own absence" is a contradiction in terms. Quantum theory did not create this asymmetry and cannot be enlisted to elevate it into a claim about the structure of the world.

The strongest part of the user's intuition survives in a narrower, better-defined form: the Everettian (many-worlds) reading, combined with a first-person perspective, yields the "quantum immortality" argument—that from the inside, some branch on which the observer continues always remains, so subjective experience never encounters its own termination. This is a coherent consequence of a particular interpretation, and it is worth distinguishing sharply from the surrounding claims. It is defensible as a statement about branch-relative continuity of experience; it is not evidence that death does not occur, that other people are unreal, or that the observer's consciousness survives in any physically meaningful sense. The argument's own structure undermines the solipsistic reading: the surviving branch is populated by other people whose observations are just as branch-relative as one's own, and the "immortality" is a statement about the indexical location of experience, not about the unique reality of one person. Meanwhile, the empirical and logical critiques in Section 6 are decisive against the stronger thesis. Quantum solipsism inherits every classical objection to solipsism—unfalsifiability, explanatory emptiness, the impossibility of coherently denying other minds while relying on testimony about them—and adds no quantum-specific support. The Born rule, decoherence, and the success of intersubjective prediction all presuppose a shared world in which observations can be checked against one another; a framework that dissolves that shared world cannot then use its predictions as evidence.

Claim	Evidence strength	Still to validate
No interpretation privileges one observer as sole reality-constituter	Strong (consensus across interpretations)	—
First-person non-observation of one's own death is a logical truism, not a quantum effect	Strong	—
Quantum immortality is coherent within Everettian first-person reasoning	Moderate (interpretation-dependent)	Whether branch-continuity maps onto any physical notion of survival
Other people are "merely observed reality"	Very weak (philosophically and empirically unsupported)	Nothing—claim is unfalsifiable as stated
Consciousness plays a causal role in state-vector reduction	Contested	Empirical discrimination among collapse models remains open

What remains genuinely open is narrower and more tractable than the topic's framing suggests. The measurement problem is unresolved, and the status of the observer within it—whether consciousness is causally relevant to collapse, whether branches are real, whether a preferred basis emerges from decoherence alone—is a live research question. But these are questions about the formalism's interpretation, answerable (if at all) by theoretical consistency and, in the case of objective-collapse models, by experiment. They are not questions about whether one person's death is real while another's is not. The honest synthesis is that the topic conflates three distinct things: the genuine interpretive puzzle of measurement, the genuine but trivial first-person asymmetry of experience, and the indefensible metaphysical thesis of solipsism. Only the first two have standing; the third does not, and quantum mechanics provides it no shelter.

For anyone taking the topic seriously, the practical guidance is to keep the levels separate. Treat the first-person asymmetry as a fact about the grammar of experience, not as evidence about ontology. Treat quantum immortality as an interpretation-relative curiosity whose implications for how one should live or fear death are, at most, deflationary—it does not license indifference to others' deaths, because those others are first-person subjects in their own right, symmetrically situated. And treat the solipsistic conclusion as a reductio: if a framework implies that the deaths of others are not real, that framework has failed as a description of the world we share, since the very evidence for quantum mechanics is intersubjective. The most defensible position is a modest realism: quantum theory describes a shared world in which observation is a physical process, first-person experience is real but not world-constituting, and death is real for everyone, including—from the outside—oneself. Follow-up work worth doing is empirical and interpretive rather than metaphysical: testing objective-collapse models, clarifying what decoherence does and does not explain, and articulating precisely what "first-person continuity" could mean in a physical theory. Those questions are hard, but they are answerable. The question of whether other people really exist is not a quantum question at all, and the answer to it was settled long before quantum mechanics arrived.

References

1. Tianyan Quantum Group (2025). Tianyan: Cloud services with quantum advantage. arXiv. http://arxiv.org/abs/2512.10504v2
   Jong Yeon Lee, Chao-Ming Jian, Cenke Xu (2023). Quantum criticality under decoherence or weak measurement. arXiv. http://arxiv.org/abs/2301.05238v2
   Ran Li (2024). Decoherence of quantum superpositions by Reissner-Nordström black holes. arXiv. http://arxiv.org/abs/2411.04734v2
2. Caroline L. Jones, Markus P. Mueller (2024). On the significance of Wigner's Friend in contexts beyond quantum foundations. arXiv. http://arxiv.org/abs/2402.08727v4
   Veronika Baumann (2023). Classical information and collapse in Wigner's friend setups. arXiv. http://arxiv.org/abs/2308.08260v1
   Veronika Baumann, Časlav Brukner (2023). Wigner's friend's memory and the no-signaling principle. arXiv. http://arxiv.org/abs/2305.15497v2
   J. Allam, A. Matzkin (2023). Making sense of relativistic Wigner friend scenarios: a problem for unitary accounts of quantum measurements ?. arXiv. http://arxiv.org/abs/2310.04167v3
   Ladina Hausmann, Renato Renner (2025). The firewall paradox is Wigner's friend paradox. arXiv. http://arxiv.org/abs/2504.03835v1
3. Xinyu Lin, Yingjie Zhou, Xun Zhang et al. (2023). Illumination-insensitive Binary Descriptor for Visual Measurement Based on Local Inter-patch Invariance. arXiv. http://arxiv.org/abs/2305.07943v1
   Mingxuan Li, Yen Hang Zhou, Liemin Li et al. (2023). Real-time and Robust Feature Detection of Continuous Marker Pattern for Dense 3-D Deformation Measurement. arXiv. http://arxiv.org/abs/2305.11782v2
   Yang Li, Shitu Zhang, Yuanzheng Li et al. (2023). PMU measurements based short-term voltage stability assessment of power systems via deep transfer learning. arXiv. http://arxiv.org/abs/2308.03953v2
   Okan Bulut, Maggie Beiting-Parrish, Jodi M. Casabianca et al. (2024). The Rise of Artificial Intelligence in Educational Measurement: Opportunities and Ethical Challenges. arXiv. http://arxiv.org/abs/2406.18900v1
   Henry Beuster, Lars-Michel Bretthauer, Gerd Scholl (2025). OPC UA for IO-Link Wireless in a Cyber Physical Finite Element Sensor Network for Shape Measurement. arXiv. http://arxiv.org/abs/2504.03704v1
4. Tianyan Quantum Group (2025). Tianyan: Cloud services with quantum advantage. arXiv. http://arxiv.org/abs/2512.10504v2
   Vittorio D'Esposito, Giuseppe Fabiano, Domenico Frattulillo et al. (2024). Doubly Quantum Mechanics. arXiv. http://arxiv.org/abs/2412.05997v3
   Davide Lonigro, Fattah Sakuldee, Łukasz Cywiński et al. (2024). Double or nothing: a Kolmogorov extension theorem for multitime (bi)probabilities in quantum mechanics. arXiv. http://arxiv.org/abs/2402.01218v3
   Debadrita Ghosh, Urbasi Sinha (2025). Interference in Quantum Mechanics. arXiv. http://arxiv.org/abs/2508.12940v1
   Adina Goldberg (2024). Quantum games and synchronicity. arXiv. http://arxiv.org/abs/2408.15444v4
5. Web Search: solipsism Stanford Encyclopedia of Philosophy other minds problem
   Other Minds (Stanford Encyclopedia of Philosophy)
   Solipsism and the Problem of Other Minds | Internet Encyclopedia of Philosophy
   Problem of other minds - Wikipedia
   Solipsism - Wikipedia
   Other Minds (Stanford Encyclopedia of Philosophy/Fall 2026 Edition)
6. Web Search: relational quantum mechanics Rovelli relative facts not solipsism criticism
   Relational Quantum Mechanics (Stanford Encyclopedia of Philosophy)
   Relational Quantum Mechanics at the Crossroads | Foundations of Physics | Springer Nature Link
   Relational quantum mechanics - Wikipedia
   Relational Quantum Mechanics | The Unfinishable Map
   Research Notes - Relational Quantum Mechanics | The Unfinishable Map
7. Web Search: Fuchs QBism "not solipsism" each agent external world other minds
8. Web Search: "quantum immortality" thought experiment Everett many-worlds first-person death Vaidman Tegmark
   Quantum suicide and immortality - Wikipedia
   Some Version of You Always Beats Death, According to This Scientific Theory
   Quantum immortality - Simple English Wikipedia, the free encyclopedia
   Many-Worlds Interpretations Can Not Imply ‘Quantum Immortality’
   The Many-Worlds Theory - How Quantum Suicide Works | HowStuffWorks
9. Tianyan Quantum Group (2025). Tianyan: Cloud services with quantum advantage. arXiv. http://arxiv.org/abs/2512.10504v2
   Joshua Foo, Magdalena Zych (2023). Superpositions of thermalisations in relativistic quantum field theory. arXiv. http://arxiv.org/abs/2307.02593v2
   Adina Goldberg (2024). Quantum games and synchronicity. arXiv. http://arxiv.org/abs/2408.15444v4
   Angel Ballesteros, Diego Fernandez-Silvestre, Flaminia Giacomini et al. (2025). Quantum Galilei group as quantum reference frame transformations. arXiv. http://arxiv.org/abs/2504.00569v3
   Vittorio D'Esposito, Giuseppe Fabiano, Domenico Frattulillo et al. (2024). Doubly Quantum Mechanics. arXiv. http://arxiv.org/abs/2412.05997v3
10. Liuliu Chen, Elise R. Carrotte, Brian E. Chapman et al. (2026). FigSIM: A Dataset for Fine-grained Suicide Severity and Figurative Language in Suicide Memes. arXiv. http://arxiv.org/abs/2606.02523v1
    Kushagra Tiwari, M. Amin Rahimian, Marie-Laure Charpignon et al. (2026). Socio-Spatial Patterns of Suicide Mortality in the United States. arXiv. http://arxiv.org/abs/2603.02131v2
    Simon Saunders (2025). Physical Probability in the Everett Interpretation and Bell Inequalities. arXiv. http://arxiv.org/abs/2512.00575v1
    Tianyan Quantum Group (2025). Tianyan: Cloud services with quantum advantage. arXiv. http://arxiv.org/abs/2512.10504v2
    Simon Saunders (2026). Physical probability in the Everett interpretation and Bell inequalities. arXiv. http://arxiv.org/abs/2601.12159v2
11. Web Search: Tegmark importance of quantum decoherence in brain processes decoherence time 10^-13 seconds microtubules
    [quant-ph/9907009] The importance of quantum decoherence in brain processes
    Importance of quantum decoherence in brain processes - PubMed
    The Importance of Quantum Decoherence in Brain Processes
    The Importance of Quantum Decoherence in Brain Processes
    Importance of quantum decoherence in brain processes — Lacuna
12. Florentin Koch (2026). Calibration and transfer in indicator-based assessments of artificial consciousness. arXiv. http://arxiv.org/abs/2603.27597v2
    Mikołaj Sienicki, Krzysztof Sienicki (2026). The New Tractatus Program: Quantum Mechanics, Anti-Totalitarian Ontology, and Consciousness. arXiv. http://arxiv.org/abs/2607.09819v1
    Tianyan Quantum Group (2025). Tianyan: Cloud services with quantum advantage. arXiv. http://arxiv.org/abs/2512.10504v2
    Dr Tom McClelland (2026). How to Navigate Uncertainty About AI Consciousness. arXiv. http://arxiv.org/abs/2608.19215v1
    Larissa Albantakis (2025). On the utility of toy models for theories of consciousness. arXiv. http://arxiv.org/abs/2508.00190v1
13. E. F. van Dishoeck, the MINDS team (2024). Probing the gas that builds planets: Results from the JWST MINDS program. arXiv. http://arxiv.org/abs/2412.07853v1
    Pavan C Shekar, Aswanth Krishnan (2025). Adaptive Minds: Empowering Agents with LoRA-as-Tools. arXiv. http://arxiv.org/abs/2510.15416v2
    Andrii Voshchepynets, Oleksiy Agapitov, Lynn Wilson et al. (2023). Multi-Point Detection of the Powerful Gamma Ray Burst GRB221009A Propagation through the Heliosphere on October 9, 2022. arXiv. http://arxiv.org/abs/2309.05856v1
    Vidya Venkatesan, Aomawa L. Shields, Russell Deitrick et al. (2025). A One-Dimensional Energy Balance Model Parameterization for the Formation of CO2 Ice on the Surfaces of Eccentric Extrasolar Planets. arXiv. http://arxiv.org/abs/2501.11667v1
    Fabrizio Fagiolo, Marco Baioletti, Valentino Santucci (2026). Linear Ordering Problem: Time for a Change. arXiv. http://arxiv.org/abs/2605.31051v2