Is Reality a Construction of the Self: Frauchiger–Renner Paradox Quantum-Philosophical Perspective

Abstract

Is reality constructed by the self? This thesis explores that question through the lens of the Frauchiger–Renner paradox – a recent no-go theorem in quantum foundations that extends Wigner’s friend thought experiment. We begin by outlining the paradox, in which multiple observers using quantum theory reach logically inconsistent conclusions about a single experimental history. The paradox highlights self-referential and multi-agent aspects of quantum measurement, suggesting that classical notions of objectivity, consistency, and shared reality may fail at the quantum level. We then situate these findings within broader philosophical discourse. Perspectives from phenomenology (Husserl’s and Merleau-Ponty’s views on perception and constitution of reality), epistemology (Kant’s and Putnam’s insights on the inescapability of perspective), and metaphysics (Wheeler’s participatory realism, QBism, and relational quantum mechanics) are brought to bear.

These frameworks all converge on the idea that

..reality might not be a fixed, observer-independent entity, but instead perspectival or relational – potentially even a construction of the observing self.

We analyze how the Frauchiger–Renner paradox challenges the possibility of a third-person “God’s-eye” description of the world, revealing fundamental limits to observer-independent accounts. The implications for the nature of consciousness and the boundaries of the self are discussed, including connections to integrated information theory and metaphysical idealism (the view that mind or experience is the primary reality). We consider how different interpretations of quantum mechanics (many-worlds, objective collapse theories, epistemic approaches) address the paradox and what each implies about reality’s ontology. Finally, we reflect on how such paradoxes expose not only known gaps (e.g. measurement theory puzzles) but also possible unknown unknowns – deep structural limits on shared experience or cognition that physics is only beginning to unveil.

The conclusion supports an interdisciplinary, nuanced thesis: quantum theory and philosophy together suggest that

..reality as experienced and described is partly a construct of the self – or at least cannot be cleanly separated from the perspective of the observer.

Introduction

Is reality observer-dependent?

In the quantum realm, the act of observation seems to participate in “bringing into being” phenomena. The Frauchiger–Renner paradox sharpens this question by considering multiple observers whose quantum-mechanical reasoning about each other leads to contradictory conclusions.

Modern physics has profoundly altered our understanding of “reality.” Quantum mechanics in particular often forces us to reconsider the relationship between the observer (or “self”) and the observed world. A striking recent development in this discourse is the Frauchiger–Renner paradox, a thought experiment formulated by Daniela Frauchiger and Renato Renner (2018) (Wigner's friend - Wikipedia). This paradox builds on Eugene Wigner’s famous “friend” scenario and suggests that quantum theory, when applied to observers themselves, can yield inconsistent narratives (Wigner's friend - Wikipedia) (Wigner's friend - Wikipedia). At face value, this challenges the classical ideal of a single, observer-independent reality that all rational agents can agree upon. Instead, it appears to point toward a more relative or participatory notion of reality, where different observers might legitimately hold different “facts” about the world (Relational quantum mechanics - Wikipedia) ([1902.05080] Experimental test of local observer-independence).

This thesis undertakes a deep interdisciplinary analysis of the question: “Is reality a construction of the self?” We use the Frauchiger–Renner (FR) paradox as a central case study to ground the discussion. In quantum foundations, FR is a no-go theorem demonstrating that certain reasonable assumptions (about how observers use quantum mechanics and about a single, objective world) cannot all be true simultaneously (Wigner's friend - Wikipedia). By examining these assumptions and how the paradox arises, we gain insight into whether what we call “reality” might depend on the perspective of the observer (the self).

We proceed as follows. First, we provide an overview of the Frauchiger–Renner paradox (and its Wigner’s friend origins) in Section 1. We explain the thought experiment’s setup, its reliance on self-referential reasoning by multiple quantum-aware agents, and exactly how it produces a logical contradiction. Key concepts here are observer-relative facts and the breakdown of trans-personal consistency – ideas that will then be connected to philosophical notions of reality. We highlight how the paradox forces a choice between dropping one of three assumptions: (Q) the universal validity of quantum theory (even for observers), (C) consistency of reasoning across observers, or (S) the single-outcome (single reality) hypothesis (Wigner's friend - Wikipedia).

In Section 2: Literature Review and Background, we widen the scope. We discuss classical assumptions about objectivity and how quantum mechanics has long challenged them (e.g. the measurement problem and Schrödinger’s cat). We then introduce relevant philosophical frameworks: (i) Phenomenology – Husserl’s concept of the world as constituted in consciousness, and Merleau-Ponty’s view of perception as an interactive, embodied relation – which both suggest that what we experience as reality is intimately linked to the structure of our experience. (ii) Epistemology and Kantian philosophy – Kant famously argued that we never access the “thing-in-itself” directly, only phenomena filtered through our a priori forms of intuition and understanding; Putnam’s “internal realism” similarly rejects a God’s-eye view of truth ([DOC] Kant and Putnam: Internal Realism and Truth - PhilArchive). These ideas imply that the “world” we know is partly a construction of our conceptual apparatus. (iii) Metaphysics of observer-participation – e.g. John Wheeler’s participatory universe (“no phenomenon is real until observed” (John Wheeler’s Participatory Universe)), QBism’s agent-centered quantum interpretation, and Carlo Rovelli’s relational quantum mechanics, which explicitly posits that facts are only defined relative to an observer (Relational quantum mechanics - Wikipedia). By linking these to the FR paradox, we can ask: Does the paradox vindicate an ontology where reality is perspectival (varying with the observer’s viewpoint) rather than absolute?

Next, Section 3: Formal Analysis of the Paradox delves into the FR scenario in detail. We step through the gedankenexperiment: two “friends” inside laboratories perform quantum measurements (including a quantum coin toss and spin measurement), while two super-observers (Wigner-type agents) outside the labs also make observations and predictions. Each agent uses standard quantum mechanics to reason about others’ outcomes. We show how their inferences lead to a contradiction – specifically, a case where one outside observer (Alice) is certain that a coin toss was “tails”, while the other outside observer (Bob) is certain the very same coin toss was “heads” (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine). Both Alice and Bob’s conclusions are internally correct given their knowledge and quantum theory, yet they conflict – a logically impossible situation if there is one single reality. We analyze which assumptions must be abandoned to resolve this, and find that maintaining a single, observer-independent reality (assumption S) along with universally valid quantum theory (Q) and basic logical consistency (C) is untenable (Wigner's friend - Wikipedia). This section will use a bit of probability logic (to outline the reasoning each agent follows) and may reference the formal structure of the argument in the literature (Wigner's friend - Wikipedia). We also review empirical and theoretical responses: for example, an experimental analog by Proietti et al. (2019) implemented a variant of the scenario with entangled photons and found results implying that “quantum theory should be interpreted in an observer-dependent way” ([1902.05080] Experimental test of local observer-independence).

In Section 4: Philosophical Reflection and Synthesis, we bring the results of the formal analysis into dialogue with broader philosophical positions. We consider what it means if reality is observer-dependent. Is the FR paradox telling us that there is no single “view from nowhere”, only views from somewhere (each observer’s standpoint)? We connect this with phenomenology: Husserl, for instance, suggested that “the physical world is merely a representation of our conscious experiences”, and that “the reality we perceive is constructed through our individual consciousness” (30 Best Edmund Husserl Quotes With Image | Bookey). This resonates strongly with the idea that each quantum “observer” in FR essentially has their own reality. Merleau-Ponty likewise noted that a child initially believes in one absolute world shared by all, but an adult realizes each of us is limited to a certain point of view (Maurice Merleau-Ponty Quotes (Author of Phenomenology of Perception)). In FR, the assumption of a single shared reality leads to paradox, much as the child’s naive realism eventually must give way to an understanding of multiple perspectives.

We also consider Kant’s transcendental idealism: Kant would say we inevitably impose forms (like space, time, causality) on phenomena; we never know the noumenon (reality “in itself”). Applied to FR, one might say that each observer’s “reality” is a phenomenon for that observer, and trying to combine them into a noumenal single account runs into trouble. In a similar vein, Hilary Putnam argued against a strict metaphysical realism, advocating that truth and reality are inseparable from our conceptual schemes ([DOC] Kant and Putnam: Internal Realism and Truth - PhilArchive). “Like Kant, Putnam does not believe we can arrive at a conception of reality independent of our concepts and our inescapably human perspective.” ([DOC] Kant and Putnam: Internal Realism and Truth - PhilArchive). The FR paradox could be viewed as a concrete quantum mechanical illustration of this principle: there is no view from nowhere that all agents can consistently share.

From the perspective of quantum interpretations, we discuss how different approaches either embrace or avoid the idea of observer-constructed reality. For example, Relational Quantum Mechanics (RQM) explicitly drops the assumption (C) that one agent’s facts must be valid for another ([1902.07139] Relational analysis of the Frauchiger--Renner paradox and interaction-free detection of records from the past). In RQM, if Friend (inside the lab) has observed a result, that fact is real for the Friend; but for Wigner (outside), the Friend+lab can still be in a superposition until he interacts with them (Relational quantum mechanics - Wikipedia). As Rovelli puts it, “there is no privileged, ‘real’ account” – quantum states and events are relative to the observer (Relational quantum mechanics - Wikipedia). This relational view aligns with a perspectival ontology: reality is a network of relations, not a collection of absolute properties. We will see that within RQM the Frauchiger–Renner paradox disappears because it was premised on combining two observers’ certainties in a single framework, something RQM disallows ([1902.07139] Relational analysis of the Frauchiger--Renner paradox and interaction-free detection of records from the past). Likewise, QBism (Quantum Bayesianism) takes the quantum state to be an agent’s personal information; each observer-agent in QBism experiences their own “outcome” as a personal event, and it makes no sense to demand a unified account of two agents’ private experiences ([2008.03572] Respecting One's Fellow: QBism's Analysis of Wigner's Friend) ([2008.03572] Respecting One's Fellow: QBism's Analysis of Wigner's Friend). As the QBists Fuchs and collaborators note, Wigner’s friend paradox “poses no paradox for QBism” because Wigner and Friend are on equal footing, each using quantum theory for their own experiences ([2008.03572] Respecting One's Fellow: QBism's Analysis of Wigner's Friend). No one’s perspective is privileged or “more real” than another’s in QBism – a kind of “quantum Copernican principle” ([2008.03572] Respecting One's Fellow: QBism's Analysis of Wigner's Friend) that echoes the democratic perspectivism of phenomenology.

We will contrast these perspectival interpretations with more objectivist interpretations. The Many-Worlds Interpretation (MWI) keeps quantum theory universal (assumption Q) but abandons single outcomes (S) – effectively asserting that all outcomes happen, each in its own branch of the multiverse (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine). Many-worlds restores consistency by saying Alice and Bob’s contradictory facts actually pertain to different branches of reality; there is no single world where they both occur (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine) (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine). This salvages objectivity at the expense of an intuitively shared world. We examine whether MWI truly implies reality is not constructed by the self (since the wavefunction and its branching are taken as real and observer-independent), or whether even in MWI each observer can only ever experience one branch (thus an experiential reality that is still subjective). We also consider objective-collapse theories (e.g. GRW, or proposals tying collapse to gravity or consciousness). These theories modify quantum mechanics (drop assumption Q) such that superpositions of large systems actually collapse automatically. In an objective-collapse resolution, perhaps Wigner’s friend paradox cannot even arise, because a conscious observer’s measurement outcome would spontaneously become a single reality for everyone by physical law. However, such theories must introduce new mechanisms and are experimentally constrained. Interestingly, some recent work by Chalmers & McQueen (2021) has even suggested that consciousness itself might trigger collapse – using Integrated Information Theory (IIT) as a quantitative measure of consciousness to modify the dynamics (). In their model, when a system (like a brain) has high integrated information, it resists being in superposition and induces collapse, thus ensuring that conscious observers don’t end up in bizarre superpositions (). This is a speculative but fascinating attempt to merge the observer (mind) into the physics: if successful, it would explicitly make reality-dependent on consciousness in a formal way. We will discuss this and other attempts to incorporate the “self” or mind into quantum theory (Wigner himself advocated that consciousness breaks the chain of entanglement and produces definite outcomes (This Twist on Schrödinger's Cat Paradox Has Major Implications for Quantum Theory | Scientific American)).

Finally, Section 5: Conclusion will synthesize the insights and stake out an answer to the thesis question. In summary, we will argue that the Frauchiger–Renner paradox indeed bolsters the case that reality, as we can meaningfully discuss it, is not wholly independent of the self/observer. The paradox exposes a limit to how objective or third-person our descriptions can be: trying to maintain a single, observer-independent narrative for all observers leads to inconsistency. This suggests that each observer has a role in constituting their observed reality. Such a viewpoint finds resonance in philosophy (from Kant to phenomenology to contemporary pragmatism) and in certain interpretations of quantum mechanics (QBism, RQM, Wheeler’s participatory realism). We note, however, that this need not collapse into solipsism – rather, it points toward a relational ontology where reality is interaction-dependent or experience-dependent. We also acknowledge open questions: Are there “unknown unknowns” here? Could it be that our classical logic or assumptions about knowledge are what fail, rather than reality per se? The FR paradox might be hinting at new physics or new logic required to fully reconcile subjective experiences into a coherent whole (Wigner's friend - Wikipedia) (Wigner's friend - Wikipedia). In any case, it dramatizes that any attempt to describe the world must include the describer – a lesson long emphasized by philosophers but now made unavoidable by quantum mechanics. In a poetic sense, physics is rediscovering an ancient truth: reality and the perceiving self are inextricably intertwined. Thus, while it may be too strong to claim “the self creates reality” (there are undeniable regularities and constraints outside us), we conclude that reality as experienced and known is invariably constructed in a dialogue with the self. The observer is not a passive mirror of reality, but an active participant in its emergence (John Wheeler’s Participatory Universe) (John Wheeler’s Participatory Universe).

1. Frauchiger–Renner Paradox: Quantum Theory Looks at Itself

1.1 Wigner’s Friend: When the Observer is Observed

To appreciate the Frauchiger–Renner paradox, one must first understand its precursor: Wigner’s friend. Eugene Wigner in 1961 posed a simple yet profound scenario: Imagine a physicist’s friend performing a quantum measurement inside a closed laboratory (for example, measuring the state of a atom or seeing whether Schrödinger’s cat is alive or dead), while Wigner himself stands outside the lab, isolated from the experiment (This Twist on Schrödinger's Cat Paradox Has Major Implications for Quantum Theory | Scientific American). From the friend’s perspective, the experiment yields a definite outcome – she either sees (for instance) the cat alive or dead, collapsing the quantum state in the usual Copenhagen sense. But from Wigner’s perspective (treating the lab plus friend as one big quantum system), no collapse has occurred for him until he opens the door. Until that moment, quantum theory would have Wigner consider the friend+cat to be in a superposition of “friend saw alive” and “friend saw dead.” This leads to a seeming paradox: can the friend really have a single outcome (a single reality) while Wigner still sees a superposition? Are there two realities, one for the friend and one for Wigner? Wigner argued that it is absurd to think of a conscious friend as being in a superposition of two mental states (This Twist on Schrödinger's Cat Paradox Has Major Implications for Quantum Theory | Scientific American) – thus he leaned towards the idea that the act of conscious observation by the friend forces the outcome to be definite (collapse), implying standard quantum mechanics might need an upgrade when it comes to conscious observers (Wigner's Friend) (Wigner's Friend). This was one of the earliest suggestions that consciousness might play a special role in quantum mechanics – a controversial idea connecting physics with the self.

Regardless of one’s stance on consciousness causing collapse, the Wigner’s friend thought experiment clearly illustrates the problem of “observer-relative facts.” To Wigner, before he opens the lab, it is a fact that “the quantum state is still a superposition.” To the friend, it is a fact that “the outcome is, say, a decayed atom and dead cat.” Both cannot be directly compared because the friend’s fact is inside the lab. If Wigner trusts quantum theory fully, he might even do an interference experiment on the whole lab to verify the superposition (in principle). Wigner’s friend paradox thus “shows that things can become very weird if the observer is also observed” (This Twist on Schrödinger's Cat Paradox Has Major Implications for Quantum Theory | Scientific American). It questions the objectivity of measurement outcomes: are they absolute, or only defined relative to a particular observer who has the information?

Over the decades, various interpretations of quantum mechanics answered Wigner’s puzzle differently (we will revisit these in Section 4). But it remained somewhat academic, because one could always say: “Well, in practice once a human observes something, decoherence ensures any superposition is inaccessible; so Wigner would never actually see a contradiction.” The Frauchiger–Renner paradox revives and extends this issue in a sharper form, by considering multiple interacting “Wigners” and “friends”, and showing that even without invoking consciousness explicitly, quantum theory used consistently by all agents leads to a logical contradiction. In other words, Frauchiger and Renner proved a theorem that if we assume that quantum mechanics can describe complex observers and that these observers can consistently reason about each other, we run into a paradox (Wigner's friend - Wikipedia) (Wigner's friend - Wikipedia). This raises the stakes: it’s not just about consciousness, but about whether quantum mechanics can be universally valid and objective at the same time.

1.2 The Frauchiger–Renner Gedankenexperiment

At heart, the Frauchiger–Renner (FR) scenario is an extended Wigner’s friend experiment involving four agents (two “friends” inside labs, and two “Wigners” outside) and a clever protocol of measurements that forces a contradiction. We can outline the scenario step by step (following Frauchiger & Renner’s original and simplified expositions (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine) (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine)):

• Setup with biased quantum coin: Friend 1 (let’s call her F1) inside Lab1 performs a quantum coin toss. This could be a qubit prepared in state |heads⟩ with probability 1/3 and |tails⟩ with 2/3, so that the outcome “tails” is more likely (2/3 chance) (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine). The state of the coin can be written as $\sqrt{\frac{1}{3}}|H⟩ + \sqrt{\frac{2}{3}}|T⟩$. This bias is set to obtain certain logical relations later.
• Friend 1’s measurement and state preparation: F1 measures the coin. If the coin came up Heads, F1 prepares a qubit (call it qubit S) in state $|↓\rangle_S$ (spin-down). If the coin was Tails, F1 prepares qubit S in state $|→\rangle_S$ which is a superposition of up and down (specifically $|→\rangle = \frac{1}{\sqrt{2}}(|↑\rangle + |↓\rangle)$, an equal superposition of spin-up and spin-down) (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine). F1 then sends this qubit S into Lab2 (to Friend 2). Importantly, F1 also records her coin outcome (heads or tails) in her memory.
• Friend 2’s measurement: Friend 2 (call him F2) in Lab2 receives qubit S and measures it in the ${|↑\rangle, |↓\rangle}$ basis (i.e. measures spin-up vs spin-down). Based on how S was prepared: if F1 had tails, S was $|→\rangle = \frac{1}{\sqrt{2}}(|↑\rangle + |↓\rangle)$, so F2 has 50% chance to see $↑$ and 50% to see $↓$. If F1 had heads, S was $|↓\rangle$, so F2 will certainly see $↓$. Thus:F2 also notes his result (call it YES if $↑$, NO if $↓$, for reasons that will become clear).
  • If F2 sees result $↑$ (spin up), he can infer with certainty that F1’s coin must have been tails (because heads could not have led to $↑$) (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine) (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine).
  • If F2 sees $↓$, it could be either heads or tails scenario (heads leads always to $↓$, tails leads sometimes to $↓$), so $↓$ doesn’t allow a definite inference about the coin.
• External observers (Wigners) step in: Now we have two labs: Lab1 containing F1 (who has coin result recorded and knows which state she sent), and Lab2 containing F2 (who has his measurement result). Outside each lab we have an observer: Wigner_A (Alice) outside Lab1, and Wigner_B (Bob) outside Lab2. These observers will perform measurements on the entire labs (including the friends). Specifically, Alice will later measure Lab1 in a basis that effectively checks the state of F1 and her coin memory; Bob will measure Lab2 in a basis related to F2’s state.
• Alice’s measurement on Lab1: Alice waits until F1 has done everything (coin toss and sending qubit) and then performs a “big” measurement on Lab1 (the friend plus her coin). The clever choice is for Alice to measure in a basis that asks: “Is F1’s coin result Tails AND whatever she did (preparing and sending qubit) consistent with that?” In practice, Alice’s measurement can project onto a state corresponding to “F1’s memory is Tails AND the coin and lab are in the quantum state consistent with tails outcome” versus the orthogonal subspace. Let’s call the particular outcome Alice might get as “Alice = OK” (or simply, A = OK) if Lab1 is in the state consistent with tails, and “Alice = FAIL” if not. In essence, A = OK corresponds to F1 having observed Tails (which means she prepared the $|→\rangle$ state for S) and indeed her lab state is that (not something else). If F1 had Heads, Alice’s measurement is designed to yield FAIL with certainty (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine). If F1 had Tails, Alice could get OK or FAIL, with some probabilities given the state overlaps. (Details aside, we know from FR that with their bias 1/3 vs 2/3, the probabilities work out so that certain inferences become logical certainties.)When Alice gets OK (yes) for her measurement, she knows F1’s coin was Tails with certainty (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine). (This is because if the coin had been Heads, the Lab1 state would never yield the OK outcome.) So Alice infers “Coin = Tails” whenever she sees OK (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine).
• Bob’s measurement on Lab2: Similarly, Bob measures the entirety of Lab2 (F2 and qubit S etc.) in a basis chosen such that one particular outcome corresponds to “F2’s measurement was $↑$ (YES result) and consistent with that situation.” If Bob gets his desired outcome (call it B = OK or “Bob = YES” in some descriptions), he can infer that F2 saw $↑$, which as we noted implies F1’s coin was Tails. Conversely, if Bob gets the other outcome, it would align with F2 seeing $↓$ or an inconsistent state. So Bob infers “Coin = Heads” if he sees his special outcome (because if F2 saw $↑$, coin was tails, and Bob’s special outcome is actually associated to F2’s complementary result… we need to be careful: FR’s paradox comes when Alice and Bob both claim opposite coin results). In the FR setup, Bob’s “Yes” outcome is actually tied to F2’s result $↓$ indicating Heads – the construction is symmetric to yield the contradiction. In fact, Frauchiger & Renner set it so that Bob’s certainty goes the other way: Bob’s successful inference is that coin was Heads (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine).

Putting it together in simpler terms: After all measurements, Alice might announce “I am certain the coin was tails,” and Bob might announce “I am certain the coin was heads.” Normally, that’s impossible – the coin can’t have been both. But FR show that with quantum mechanics each of them can indeed be certain of these opposite facts in the same run of the experiment (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine) (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine). They calculated the probability of this contradictory situation to be nonzero (specifically 1/12 ≈ 8.3% chance) (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine) given the initial state biases. Thus, we have a paradox: quantum theory seemingly allows two rational agents to arrive at opposite conclusions about a single historical event (the coin toss). All of their reasoning steps were each 100% correct under quantum rules, yet they conflict.

Let us articulate the core assumptions that lead to the contradiction, as identified by Frauchiger & Renner (Wigner's friend - Wikipedia):

• (Q) Universal validity of quantum mechanics: Each agent (friend or Wigner) is assumed to use standard quantum theory for any system, even ones that include other observers. In particular, if something has probability 0 or 1 (happens with certainty) according to quantum calculation, the agents treat that as a sure fact. (Using the Born rule for probability-1 events as certainty (Wigner's friend - Wikipedia).)
• (C) Consistency of reasoning: If one agent infers a fact with certainty, that fact can be used by another agent in their reasoning. In the paradox, this was used when, for example, F2’s knowledge that “if I saw $↑$, coin was tails” is assumed to be also usable by Bob; or when Alice assumes that if Bob is certain of something, she can take it into account. In other words, different observers’ predictions are assumed to not contradict each other if all are using quantum theory correctly (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine). This is like a “transitivity of knowledge” or mutual consistency assumption.
• (S) Single outcome (single world): The experiment has one actual result. The coin was either Heads or Tails (not both), each friend sees one outcome, each Wigner gets one outcome, etc. There is one reality that all these observations pertain to. (This rules out the Many-Worlds interpretation where effectively both Heads and Tails could happen in separate branches.)

Frauchiger and Renner prove that (Q)+(C)+(S) cannot all hold (Wigner's friend - Wikipedia). In a nutshell, quantum mechanics plus logical consistency plus a single shared reality leads to a contradiction. If quantum theory is universally valid (Q) and we insist on a single-world (S), we must give up consistency (C) – meaning we accept that different observers cannot straightforwardly combine their knowledge without running into trouble. Alternatively, if we keep consistency and a single reality, then quantum mechanics (at least its usual interpretation for observers) must break down somewhere (perhaps needing a new theory or collapse mechanism). Or one can keep quantum theory and consistency by accepting multiple outcomes (many-worlds, violating S).

Frauchiger–Renner’s own conclusion was phrased provocatively: “Quantum theory cannot consistently describe the use of itself.” (Wigner's friend - Wikipedia) In other words, you can’t have a “quantum observer observing another quantum observer” and expect the theory to make sense in a single world. This suggests some fundamental limit to objectivity: you can’t have two agents both applying quantum theory to each other and end up with a coherent single reality. The paradox doesn’t say quantum theory is “wrong” – rather it says at least one of our intuitive principles must give way. As a Nature News & Views commentary on the FR result put it, “Frauchiger and Renner have recently claimed to prove that ‘Single-world interpretations’ of quantum theory cannot be self-consistent.” (An inconsistent friend | Semantic Scholar). This is a dramatic statement: it means if we believe there’s one world, we might have to change how we think about quantum theory or its domains of applicability.

1.3 Responses and Resolutions: What Gives?

The FR paradox has spurred many responses in the literature, each essentially choosing a different assumption to question. Here is a brief summary of how one might escape the paradox (each path will tie into more philosophical discussion later):

• Many-Worlds (Drop S): If we deny that there is a single, unique outcome for each measurement, then there is no contradiction – Alice’s “tails” world and Bob’s “heads” world are two different branches. In Many-Worlds Interpretation (MWI), whenever a quantum measurement happens, the universe splits. So F1’s coin toss leads to a branch with Heads and one with Tails. In the branch where it was Heads, Alice will get FAIL and Bob... (their results will diverge accordingly). MWI would say Alice and Bob never actually find themselves in the same branch both announcing contradictory facts. In the branches where Alice finds “OK” (meaning tails), Bob in most of those will not get “OK” (contradiction avoided in each branch). In the rare branch where in quantum amplitudes Alice and Bob would both get OK (the 1/12 scenario), MWI actually says that scenario corresponds to an inconsistent branch with zero amplitude – effectively it does not exist as a realized world. Thus, MWI can maintain that each observer’s perspective is correct in their branch, and there is no single narrative linking them without branching (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine) (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine). The cost is a very extravagant ontology (the multitude of worlds), but one that treats the wavefunction as a complete description of reality. In MWI, reality is perhaps less a construction of the self (since the wavefunction of the multiverse is objectively real), but one could argue that since no single observer ever experiences the multiverse – only their branch – each observer still has their own reality (one branch out of many).
• Relational/Subjectivist (Drop C): Several analysts (including Frauchiger & Renner themselves in some remarks, and others like Brukner, Healey, and the relational QM camp) suggest that the fault is assuming that different observers’ knowledge can be directly compared. If we reject the consistency condition (C), we say: Alice’s certainty is valid for Alice, and Bob’s for Bob; but there is no requirement that they can be combined into a single logical frame. This is exactly the position of Relational Quantum Mechanics (RQM) – it declares that facts are relative. As one paper title puts it, “our analysis shows that the paradox disappears if one rejects promoting one agent’s certainty to another agent’s certainty when it cannot be validated by records from the past.” ([1902.07139] Relational analysis of the Frauchiger--Renner paradox and interaction-free detection of records from the past). In plain terms, Wigner (or Alice) cannot simply assume the truth of Friend’s observations unless she has physically interacted with the Friend’s records. Until then, “Friend saw tails” is not a fact for Wigner. RQM would say each interaction (observation) creates facts, but a fact for one observer need not be a fact for another if no causal communication bridge exists ([1902.07139] Relational analysis of the Frauchiger--Renner paradox and interaction-free detection of records from the past). QBism similarly insists that quantum states and probabilities are an agent’s personal degrees of belief; one agent cannot plug in another agent’s belief as if it were a factual state of the world ([2008.03572] Respecting One's Fellow: QBism's Analysis of Wigner's Friend) ([2008.03572] Respecting One's Fellow: QBism's Analysis of Wigner's Friend). By this view, reality is fundamentally perspectival – there is no “view from nowhere,” only views from different somewheres. The agents can be “respectful” of each other’s perspectives but not assume they share the same state of the world until they compare notes. In FR, the contradiction arises precisely by assuming Alice can use Bob’s inferences or vice versa (each reasoning about the other’s reasoning). If we forbid that cross-reasoning (except when they come together and exchange classical information), the paradox is averted. This stance in effect says each self (observer) constructs their own reality (their own set of facts), and the problems only appear when we naive realists try to suppose there’s a single reality they’re all describing. This resolution aligns with a kind of neo-Kantian or phenomenological perspective in philosophy, as we will explore.
• Objective Collapse or New Physics (Drop Q): A third option is that standard quantum theory breaks down when applied to conscious agents or complex systems – so assumption (Q) is false. Perhaps there is an objective physical process (e.g. spontaneous collapse, or a limit of quantum linearity) that prevents situations like FR from happening in the first place. For example, an objective collapse theory like GRW would say that a superposition of a human observer and lab would collapse almost immediately, so Wigner could never see a superposition of a friend who observed a result. In FR, maybe when F1 measured the coin, that caused a genuine collapse that would make Alice’s superposition assumption invalid. This route preserves a single reality and normal logic, but requires a change in the physics – quantum mechanics would not be “universal.” Indeed, FR’s original motivation was to test the universal validity of quantum theory (Quantum theory cannot consistently describe the use of itself | Nature Communications) (Quantum theory cannot consistently describe the use of itself | Nature Communications). Their paradox suggests that if quantum mechanics is universal, then something’s got to give – so perhaps quantum mechanics is not universal. One concrete example linking to the “self”: Wigner’s hypothesis that consciousness causes collapse would solve FR: the friend’s consciousness observing the coin collapse it for everyone. Recently, as mentioned, Chalmers and McQueen’s model ties the collapse to the amount of integrated information (consciousness) in the system (). These ideas effectively put the “self” into the fundamental laws – reality would then not exactly be a construction of the self but the presence of the self would influence which reality actualizes (thus ensuring only one outcome and consistency). Such theories are speculative and controversial, but they illustrate one way to avoid the paradox by affirming that an absolute reality exists (one outcome) but noting that quantum theory is incomplete in describing how that outcome is chosen. The implication here is that quantum mechanics needs augmentation by a theory of mind or some new rule – an approach that ventures into the domain of what one might call “unknown unknowns”. Perhaps new physics will eventually explain how observers achieve a shared reality by a mechanism we do not yet understand.

Each of these resolutions carries profound metaphysical implications. We will examine those in Section 4. But first, we will step back and place the FR paradox in context: how it connects to long-standing debates about reality, knowledge, and observation. Before diving into heavy philosophy, the next section reviews how the notion of reality being observer-dependent is echoed in multiple disciplines.

2. Reality, Observers, and Perspectives: An Interdisciplinary Review

In confronting the Frauchiger–Renner paradox, we find ourselves at a crossroads of physics and philosophy. The questions it raises are not entirely new; they reverberate with inquiries that philosophers have pursued for centuries: Do we perceive reality as it truly is, or do we in some sense constitute reality through our perceptions and concepts? Is there a “view from nowhere,” or is all knowledge from a viewpoint? In this section, we connect quantum foundational issues to three intellectual traditions:

• (A) Phenomenology and the primacy of experience: how the structure of consciousness shapes reality.
• (B) Epistemology (Kantian and post-Kantian): the idea that the world-as-experienced is filtered or constructed by our mind or conceptual schema.
• (C) Metaphysics of participatory reality: ideas from physicists and philosophers that observers are not passive, but active participants in reality’s existence.

By surveying these, we’ll see that the notion of a perspectival or observer-dependent reality has deep roots and many forms. The Frauchiger–Renner paradox might be viewed as a specific scientific case forcing these philosophical issues into the open.

2.1 Phenomenology: The World as Experienced

Phenomenology, founded by Edmund Husserl in the early 20th century, is a philosophical approach that centers on examining experience as given to consciousness. Rather than assume an external world and ask how we know it, Husserl started by “bracketing” the question of the external world’s independent existence (the epoché) and analyzing how objects appear to us. In doing so, phenomenology often emphasizes that the reality we know is intimately linked to consciousness.

Husserl argued that consciousness is not a passive mirror but an active constitution of meaning. In his view, the physical world we perceive is essentially a correlatum of consciousness – it appears for us through a series of intentional acts (perceptions, judgments, etc.). A telling summary of Husserl’s view: “According to him, the reality we perceive is constructed through our individual consciousness. Our experiences color our interpretation of the physical world, limiting our knowledge to the subjective realm.” (30 Best Edmund Husserl Quotes With Image | Bookey). In other words, the world as we perceive it is not the thing-in-itself, but a world synthesized by our mind from the sensations and contexts we have. Husserl wasn’t denying an external reality outright, but insisting that whatever we say about reality is already from the perspective of consciousness – there is no getting “outside” our own experience to some pure objectivity.

Merleau-Ponty, a later phenomenologist, built on Husserl and emphasized the embodied nature of perception. For Merleau-Ponty, we are not disembodied minds gazing at a world, but embodied beings in the world. Our perception is always from a particular point of view and through our bodily interaction. One of his famous quotes: “The world is... the natural setting of, and field for, all my thoughts and all my explicit perceptions... there is no inner man, man is in the world, and only in the world does he know himself.” (Maurice Merleau-Ponty Quotes (Author of Phenomenology of Perception)). This reflects the idea that our entire cognition is situated; truth is not just inside the mind nor simply “out there,” but in the engagement between the two.

Importantly, Merleau-Ponty also discussed intersubjectivity – how we come to share a world with others. He noted that a child initially doesn’t distinguish perspectives: “The child lives in a world which he unhesitatingly believes accessible to all around him... He has no awareness of himself or of others as private subjects, nor does he suspect that all of us... are limited to one certain point of view of the world.” (Maurice Merleau-Ponty Quotes (Author of Phenomenology of Perception)). Only later do we learn that each person has their own perspective, and that what I see may not be identical to what you see. This is a crucial realization for a coherent shared reality: we must acknowledge multiple perspectives. Merleau-Ponty’s observation strikingly parallels what the FR paradox forces us to confront: the “naive child” assumption that there is one single world “accessible to all” leads to contradictions (as with Alice and Bob’s conflicting certainties). The mature view is that each observer has only a perspective on the world, not a view of the whole truth – and yet we must somehow reconcile these perspectives. In classical everyday life, we reconcile perspectives through communication and the assumption of a common world (I can show you what I saw, etc.). In quantum mechanics, the twist is that before communication, we cannot assume a common definite reality (as RQM highlights). Phenomenology tells us that the lived world – the Lifeworld (Lebenswelt) as Husserl called it – is a world of appearances for consciousness, not an absolute univocal thing.

Thus, phenomenology would be quite comfortable with the idea that reality emerges in the interaction between subject and object. It even has a technical jargon: the noema (object as experienced) and noesis (act of consciousness) together form experience. If we push this to answer “Is reality a construction of the self?”, a phenomenologist might say: Reality as experienced is certainly co-constituted by the self. This doesn’t mean you can whimsically change reality; it means the structure of your consciousness (which is largely common among humans) shapes the world that appears. For example, space and time for us are perceived in certain ways due to our embodiment; color is a construction of our visual system plus object, not purely “out there.” In FR terms, each observer’s reality (outcome) is the result of an interaction (measurement) – the outcomes are relative to that interaction. So one could draw an analogy: each quantum measurement (like each conscious perception) brings forth a concrete reality from a set of possibilities (just as Husserl says consciousness “constitutes” an object out of sensory data and intentional context).

Phenomenology also often emphasizes pre-reflective experience – the world is given to us directly in experience, and it’s only later we theorize about it. Quantum mechanics is a highly theoretical framework, but what FR highlights is that if two observers have not compared notes, there is no single experience that contains both their observations. Each has their own “phenomenology.” Only when they interact do we have a potential single experience that includes both. But by then, certain quantum facts (like interference terms) might be lost or altered.

In summary, phenomenology provides a framework in which the paradox of FR makes conceptual sense: it is problematic only if we assume an objectivist stance that all observers’ experiences must map onto one common reality at all times. Instead, if we say reality-for-F1 is what F1 observes, reality-for-Wigner is what Wigner observes, etc., then each has a valid reality and the notion of an absolute reality independent of any observer is at least not directly accessible (Husserl would say it’s an ideal limit, not something we actually experience). This doesn’t solve the physics problem, but it reframes it: perhaps FR is telling us to take the first-person perspective more seriously in physics, rather than always trying to reduce everything to a third-person view.

2.2 Epistemology: Kant, Putnam, and the Inescapability of Perspective

In Western philosophy, a key turning point in thinking about reality and the self came with Immanuel Kant. Kant’s Critique of Pure Reason (1781) argued that the mind is not a blank slate that just receives reality; rather, the mind has intrinsic structures (forms of intuition like space and time, and categories like causality) that shape any possible experience. Thus, what we call “objective experience” is a joint product of the things-in-themselves (noumena) and our mind’s contribution. We cannot know things-in-themselves directly; we only know phenomena – things as they appear to us given our cognitive apparatus. This view is termed transcendental idealism. It is not subjective idealism (Kant isn’t saying things only exist in our heads), but it is also not naive realism – the truth about the external world is not fully knowable, only the appearances are.

Kant effectively said that any observation is already filtered through the observer. If we cheekily apply that to FR: F1’s observation of the coin is “phenomenon” for F1. Wigner’s state assignment to F1+coin is his phenomenon. There is an underlying reality (maybe the “noumenal” reality of what happened), but neither can directly access the other’s phenomenon without interaction. One might say FR paradox is like two Kantian agents trying to treat phenomena as if they were noumena and getting in trouble – they assumed a God’s-eye view that doesn’t exist.

Closer to our time, Hilary Putnam in the late 20th century advocated what he called “internal realism.” This was, in part, a reaction against a strict metaphysical realism (the idea that there is a fixed total reality completely independent of us, and truth is correspondence to that reality). Putnam argued that we have no access to a “ready-made” world independent of our conceptual scheme – any description of reality we give is done in some language or theory. He famously used a model-theoretic argument to show that many different mappings of words to world could satisfy the same supposed “God’s-eye” description, thus underdetermining truth unless we accept that truth is somehow internally determined (relative to a conceptual scheme). A key quote summarizing his stance: “Like Kant, Putnam does not advocate the view that we can arrive at a conception of reality independent of our concepts and our inescapably human perspective.” ([DOC] Kant and Putnam: Internal Realism and Truth - PhilArchive). Instead, what is real is what fits coherently into the framework of our thought and experience – reality is “perspective-laden.”

In the context of the FR paradox, one could interpret that the mistake was to assume an observer-independent truth value to statements like “the coin toss result is tails.” For F1, that statement has a truth value once she’s measured. For Wigner (Alice), if she has not looked, perhaps that statement has no meaning (in quantum terms, no truth value yet). In classical thinking we’d say “Of course the coin was either H or T, even if Wigner doesn’t know.” But FR shows that assuming such an “observer-independent fact” (the coin’s result) leads to trouble when quantum predictions are involved (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine). This resembles a Putnam-like idea that truth might be epistemic (related to what can be known by whom) rather than purely metaphysical. If we require that facts be settled only when they can be commonly established (such as via communication), then we lean toward an internalist view of truth.

Another epistemological thread is the theory-ladenness of observation (Hanson, Kuhn, etc.) – the idea that what we observe depends on our frame of reference and theoretical expectations. Quantum mechanically, different observers might even use different theories (if one believes collapse, another believes many-worlds, they would describe the situation differently). However, FR assumes everyone is using the same quantum theory – so it’s not a matter of disagreeing theories, but still they disagree on facts. This is even more striking, but it underlines the point: knowledge is situated. Each observer has a different knowledge state, and quantum theory says you cannot combine those knowledge states into one without loss (due to entanglement and measurement disturbance).

From an epistemic perspective, FR paradox can be seen as highlighting the difference between first-person certainty and third-person certainty. Each agent can be certain of something from their standpoint, but no single agent (or super-agent) can be certain of all those things together without contradiction. It suggests a limitation to omniscience: no single viewpoint can be omniscient about all quantum events without breaking the rules. This resonates with Gödel-like or epistemic paradoxes: e.g., Fitch’s paradox of knowability in logic shows that “if all truths are knowable, then all truths are in fact known,” which is absurd – hinting that there may exist truths that in principle cannot be collectively known. Similarly, FR could imply there are facts that can’t be jointly known by all agents; each only can know their part. This is a kind of structural unknowability built into quantum mechanics, which epistemology can appreciate as a limit to knowledge.

Kant also had the idea of the transcendental subject – the self that is the condition for there being an experienced world at all. In FR, we might cheekily identify each quantum observer as a transcendental subject for their own “world.” The paradox might indicate there is no single “transcendental subject” for the universe (unless one imagines some ultimate observer or consciousness). If one were a metaphysical idealist, one might postulate a single Mind (like Absolute Idealism or a deity) that unifies all perspectives; absent that, we have a multiverse of perspectives.

In sum, the epistemological take-away is: Reality-as-known is perspectival. FR dramatizes this by showing even rigorous quantum inference cannot produce a globally consistent set of facts – much as Kant/Putnam assert we cannot get outside our perspective to the “view from nowhere.” To answer the question: is reality a construction of the self? – the epistemic angle suggests that whatever reality may be in itself, the only reality we can speak of scientifically or empirically is one that involves an observer’s viewpoint. Quantum mechanics seems to support that by making the observer an explicit part of the theory (via the measurement postulate or via agent-based interpretations).

2.3 Participatory Realities: Wheeler, QBism, and Relational Ontologies

We now turn to voices from physics and metaphysics that directly address the role of the observer in reality.

John Archibald Wheeler, a renowned theoretical physicist, in his later years championed the idea of the “participatory universe.” He was struck by quantum phenomena like the delayed-choice experiment, which suggested that present observations could seemingly influence past events (in terms of deciding whether light behaved as particle or wave). Wheeler proposed that “no phenomenon is a real phenomenon until it is an observed phenomenon.” (John Wheeler’s Participatory Universe) In his view, reality is not a fixed tapestry where events are laid out in spacetime once and for all; rather, it is more like a process that involves observations in bringing phenomena into being. He even speculated that the universe as a whole is participatory – that conscious observers are necessary to “bring the universe into existence” (this was a speculative idea connecting to anthropic reasoning) (John Wheeler’s Participatory Universe).

While many physicists viewed Wheeler’s ideas as philosophically provocative but hard to test, we see a resonance with FR: If no phenomenon is real until observed, then for Wigner’s friend scenario, one could say the friend’s result isn’t “fully real” to Wigner until Wigner observes it. FR paradox essentially resulted from assuming the friend’s observation was real and treating it quantum mechanically at the same time. Wheeler might say: you tried to have it both ways, but in the end, an observation must be made by someone for it to count as reality. In FR, each of the contradictory conclusions was an observation made by a different observer – no single observer saw both outcomes at once (Alice never directly sees Bob’s “coin=Heads” inference; they are deducing at cross purposes). So Wheeler’s principle hints: a phenomenon (like the coin toss outcome) can’t be both tails-for-Alice and heads-for-Bob in one observer’s frame. It’s one or the other once observed from a single frame.

Wheeler also coined the term “It from Bit,” suggesting that information (the bit) underlies the existence of things (the it). This aligns with interpretations like QBism and other informational views. In QBism (Quantum Bayesianism), championed by Fuchs, Schack, Mermin, and others, the quantum state is not an objective property but an agent’s information about their possible experiences ([2008.03572] Respecting One's Fellow: QBism's Analysis of Wigner's Friend). A quantum measurement outcome is a personal event for the agent – an update of their experience. Thus reality in QBism is fundamentally a story that each agent builds for themselves by interacting with the world. There is an external world (QBism doesn’t deny an objective world out there that we interact with), but quantum mechanics is merely an “user’s manual” for anticipating the consequences of those interactions for the agent ([2008.03572] Respecting One's Fellow: QBism's Analysis of Wigner's Friend). In the QBist view, science is about the interface between the self and the world – and quantum mechanics is very explicit about this interface, more so than classical physics was.

In the FR debate, the QBists explicitly showed that if Alice and Bob each apply quantum mechanics from their own perspective, there is no contradiction: the paradox came from trying to have a super-observer who compares their notes in a single theoretical narrative ([2008.03572] Respecting One's Fellow: QBism's Analysis of Wigner's Friend) ([2008.03572] Respecting One's Fellow: QBism's Analysis of Wigner's Friend). QBism would say: Alice’s predictions and Bob’s predictions are like two different gambling strategies based on different information; there’s no single probability assignment that a single agent has that is 0 or 1 for both events simultaneously, so no single agent is contradicting themselves. The contradiction only appears if one imagines an omniscient being who knew all of what Alice and Bob knew separately – but such a being doesn’t exist in QBism. Each agent only has their limited view. Thus, QBism offers a clear philosophical position: reality (or at least the quantum state of reality) is constructed by the agent – it is their best possible catalog of beliefs about the world’s potential to generate experiences for them. This is a radical “subjectivist” view of the quantum state, but QBists maintain that when agents do meet and compare notes, standard probability updating (Bayesian conditioning) will lead them to agreement, so it’s not solipsism, just a personalist view of science.

Relational Quantum Mechanics (RQM), which we touched on earlier, is closely aligned but with more ontological neutrality (it doesn’t emphasize belief, but relation). In RQM, an event (like “coin=Heads”) is always relative to some observer (or system). There is no God’s-eye view where you can say “the coin=Heads absolutely” – you must say “Heads relative to F1.” For Wigner, relative to him, before opening the box, it’s neither – the coin+friend system is in a superposition relative to Wigner. Only after Wigner’s interaction does “Heads or Tails relative to Wigner” become defined, and at that point, he will agree with F1. RQM thereby postulates a kind of local realism in interactions but no global realism across all observers. The ontology is one of relations: “facts” exist between interacting systems. Rovelli compares this to special relativity: just as time and simultaneity are relative to reference frames, in quantum mechanics, properties are relative to observational context (Relational quantum mechanics - Wikipedia) (Relational quantum mechanics - Wikipedia). There is no conflict between frames if you properly distinguish them, but you cannot combine them into a single frame without transformations. In quantum RQM, there is no transformation that unifies Wigner and friend’s frame because quantum measurement doesn’t allow a single unitary description that covers both after-the-fact (unless you go to many-worlds). So RQM accepts that and says “that’s just how nature is – facts are frame-dependent.” This is effectively a relational ontology – reality consists of the network of interactions (each node sees a slightly different snapshot).

These modern interpretations were foreshadowed by some earlier thinkers. We saw Wheeler and also Andrei Linde, a prominent cosmologist, who mused: “The universe and the observer exist as a pair. I cannot imagine a consistent theory of the universe that ignores consciousness.” (John Wheeler’s Participatory Universe). This statement, from a physicist, echoes the participatory sentiment – that you can’t leave the observer out of the ultimate account of reality. It’s an almost idealist statement (though Linde’s context was inflationary cosmology and the anthropic principle). Similarly, Wojciech Zurek’s ideas of “quantum Darwinism” try to explain how multiple observers end up seeing the same classical reality by interactions with the environment that “broadcast” stable information. That approach doesn’t dismiss objective reality but explains intersubjective agreement as an emergent phenomenon (so that, for example, the reason everyone sees the same pointer reading is because many bits of the environment carry that information redundantly). Quantum Darwinism upholds that there is a consistent reality that multiple observers can access, by accounting for why some observables become objective (the “pointer states”). If one pushes quantum Darwinism philosophically, it suggests that what we call objective reality is just the subset of quantum facts that are redundant enough to be accessible to many observers. The rest (like relative phases, or information not proliferated) is not “common reality.” This again is a kind of soft participatory view: the structure of interactions (what gets recorded in the environment) determines what is real-for-all vs real-for-one.

To tie these ideas back into “reality as a construction of the self”: we see that in these interpretations, the observer (self) plays an active role in carving out reality. Wheeler’s phrase “We are participants in bringing into being not only the near and here, but the far away and long ago.” (John Wheeler’s Participatory Universe) captures a bold version of this: that by observing, we might even give reality to distant events (like observing CMB photons in cosmology “completes” their history). While speculative, it’s the idea that without observers, the universe’s wavefunction might be just a vast superposition of nothing concrete. In extreme forms, this edges toward metaphysical idealism – the philosophy that mind or consciousness is the fundamental stuff of reality, and the physical world is in some sense a manifestation of consciousness.

Metaphysical idealism has had few open adherents in physics, but one can interpret Wigner as flirting with it (with his consciousness-causes-collapse theory), and likewise some modern debates on the “simulation theory” or “information as fundamental” can sound idealist (if information exists, who holds the information? Mind-like entities?). In philosophy, idealism goes back to Berkeley (“esse est percipi” – to be is to be perceived) and beyond. If one were to take FR paradox to an idealist conclusion, one might say: “Each observer’s mind effectively creates their reality. There is no independent material world – what exists are observer-moments, perhaps coordinated by some higher reality (such as a universal mind).” This is a very strong claim not warranted directly by FR, but FR certainly pokes holes in the naive materialist picture that the world’s state is completely well-defined and independent of observation. It leaves room for interpretations where mind and world jointly determine events.

For example, in the 20th century, philosopher Ernst von Glasersfeld and others developed “radical constructivism” in epistemology: the idea that knowledge is built by the subject and we cannot claim it corresponds to an ontological reality, only that it fits experience. In FR, each agent “constructs” a knowledge state. If they try to assume a God’s-eye perspective, they err.

So, the broad message across these perspectives – phenomenological, Kantian, participatory realism, QBism, RQM – is surprisingly coherent: there is no reality without an observer (or at least without a reference frame or perspective). Reality is not a monolith that we passively look at; rather, the act of observation is constitutive of what we call reality. In quantum mechanics, this is not just philosophy – it enters the mathematics and outcomes (via the measurement postulate). The Frauchiger–Renner paradox dramatizes this by showing the inconsistency that arises when we assume a completely observer-independent set of facts.

To be balanced, one should mention that not everyone agrees with these interpretations. There are ardent realists who believe there is a way out of FR paradox that preserves a single objective reality – for instance, by modifying logic (some propose using consistent histories or logical frameworks that avoid certain inference steps) or by hidden variable theories. The de Broglie–Bohm pilot-wave theory, for example, introduces a hidden variable (the particle position) so that even if Wigner doesn’t know it, the outcome is actually determined and single-valued for all (the friend saw something because the particle was actually at a definite place). In Bohmian mechanics, there is no superposition of actual configurations – the wavefunction can be superposed, but particles have definite positions that one might call the “true” state of reality. In that sense, it’s a return to classical style ontology at a deeper level. Bohmians would thus say reality is not a construction of the observers; it’s there objectively, but observers might have limited knowledge. However, even in Bohmian mechanics, there’s a twist: different observers can disagree on the quantum state (like Wigner might attribute a different wavefunction than friend), but they’d agree on actual outcomes once observed. So perhaps Bohm rescues realism at the expense of introducing a rather omniscient hidden structure that observers don’t directly see (the positions and pilot wave). It’s debatable how to interpret that philosophically (it might be seen as a kind of “God’s view” encoded in the theory, or just an unobserved reality).

Similarly, superdeterminism (another fringe idea) could avoid paradox by suggesting correlations exist since the beginning of time between what observers do and what outcomes occur, so one cannot freely set up the scenario without those biases – thus preventing the paradox. Those approaches are controversial and not widely accepted, but they aim to preserve a single reality by essentially undermining the assumptions of independence or free choice in the setup.

For the purpose of this thesis, we focus on the mainstream implications: FR pushes us toward accepting relational or perspectival reality. In answering “Is reality a construction of the self?”, the evidence from quantum foundations increasingly suggests that the self (or the agent or observer) is indispensable in any complete account of reality.

Next, we will explore concretely what this means for consciousness and the concept of self in physics, and then conclude with a synthesis of how known and unknown unknowns come into play.

3. Consciousness, Information, and the Boundaries of the Self

One intriguing aspect of the question is the role of consciousness. When we talk about “the self” constructing reality, it immediately raises the image of a conscious observer – an “I” who experiences. Does the Frauchiger–Renner paradox imply something specific about consciousness, or can it all be handled in terms of abstract “observers” (which could even be machines)? This section addresses how consciousness might figure into the story. We also discuss theories like Integrated Information Theory (IIT) which quantify consciousness, and see if they offer any insight into the measurement paradoxes. Finally, we consider whether these paradoxes hint at deeper unknown principles linking mind and physics.

3.1 Wigner’s Question: Does Consciousness Collapse the Wavefunction?

In the original Wigner’s friend scenario, Wigner himself entertained the idea that perhaps conscious observation is a special interaction that regular quantum mechanics cannot handle. He reasoned that since his friend definitely experiences a result, it seems the superposition must have collapsed at that moment. If Wigner insisted on treating the friend as just another quantum system, he got a paradox. So Wigner (1961) tentatively suggested that the quantum state “reduces” when a conscious mind observes it (This Twist on Schrödinger's Cat Paradox Has Major Implications for Quantum Theory | Scientific American). This would make consciousness the dividing line in the “Heisenberg cut” between quantum and classical.

Though this idea fell out of favor (it seemed to many to be dualistic or introducing mind mystically into physics), it has never fully gone away. It directly relates to “reality as a construction of the self” because it essentially says: the reality (definite outcomes) exist only once registered in a conscious mind. Until then, there’s just potentiality. This is an explicitly idealist stance: the mind doesn’t just know reality, it creates reality by crystallizing possibilities into one actual event.

Recent interest in this idea has been revived by considering whether one could experimentally test if consciousness causes collapse. For instance, could one have a friend who is in a superposition and then prevent them from becoming conscious of the result (say by erasing their memory quantum mechanically) to see if that avoided collapse? Some proposals involve anesthetizing a person during a measurement or using AI observers, etc., but these are far-fetched with current technology. Nonetheless, the Frauchiger–Renner paradox has re-motivated people to think carefully about the chain of measurement. In FR, the paradox doesn’t explicitly mention consciousness – the friends are simply “observers” (which could be automated labs). So FR in itself does not rely on consciousness; it would occur with any agents that can record information and make predictions. However, one might speculate: if the “friends” were not conscious, is the paradox still paradoxical? Yes, logically it is – it’s about predictions. But if one interprets that maybe a genuine paradox only arises because we treat those recordings as having the same status as conscious observations, an idealist might say: the recordings in a memory device aren’t “real” results until observed by a consciousness, thus the chain is incomplete.

While that line of thought is not mainstream, it is interesting philosophically. It suggests a hierarchy: maybe only consciousness fully “collapses” or establishes facts, whereas intermediate recordings are like latent facts that can still be in superposition. Some have argued that a thermostat or a Geiger counter isn’t fundamentally different – once information is in the environment it’s effectively a collapse. But others argue that until something is irreversibly impressed into a conscious experience, it’s not truly an observed fact. This is reminiscent of the quantum eraser experiments where you can erase which-path information; by analogy could you “erase” a friend’s memory and undo the collapse? (If the friend is treated quantum mechanically, yes in principle you could). If the friend were conscious, did that make the event irrevocable? If not, does that mean consciousness isn’t so special? These are tricky questions at the border of physics and philosophy of mind.

Penrose and Hameroff’s Orch-OR theory is one attempt that involves consciousness in physics, but through gravity-induced collapse in microtubules. It’s speculative and not widely accepted. Others, like Henry Stapp or Eugene Wigner in later years, also leaned toward mind playing a fundamental role (Stapp ties quantum collapses to conscious choices in a Whiteheadian philosophy framework).

In 2021, as mentioned, physicist Kelvin McQueen and philosopher David Chalmers collaborated on a paper exploring a Consciousness-Causes-Collapse (CCC) theory in a modern setting (). They used Integrated Information Theory (IIT) as a measure of consciousness and proposed that when a quantum system has high integrated information (like a brain state might), it triggers wavefunction collapse (they adapt a collapse model known as Continuous Spontaneous Localization, CSL). They reason that simpler versions of this idea were ruled out (because constantly collapsing any conscious brain would have observable effects that haven’t been seen), but more sophisticated versions might survive. The key takeaway is: They treat consciousness as a physical quantity (IIT’s Φ value) that can affect quantum dynamics (). If such a theory were true, it would directly make the self (since here consciousness = self in some sense) a driver of reality’s outcome. The collapse would be an action of the self onto the physical world – a stronger form of participatory realism.

While this remains hypothetical, it shows a direction some thinkers are willing to explore to integrate the self into physics. If one day experiments with quantum computers or Schrödinger cat neurons show anomalies correlated with integrated information, that would be revolutionary.

From the integrated information perspective, one might ask: does a larger integrated system (like an observer including memory) simply cannot be in certain kinds of superposition because those states would violate some integration principle? Some have speculated that maybe highly integrated systems can’t be entangled in certain ways (because that would reduce their internal integration). This is all speculative – IIT itself is a theory from cognitive science, not proven physics. But it is intriguing that serious scientists are revisiting these “consciousness collapses wavefunction” ideas with modern tools (), given how long they were marginalized. It might be because paradoxes like FR force us to consider that either we modify physics or we accept an observer-dependent reality interpretation. Both approaches have strange consequences, so all options (even old ones) deserve a fresh look.

3.2 The Self in Science: Known Unknowns and Unknown Unknowns

Physics has historically tried to remove the subjective from its descriptions – the success of Newtonian and then relativistic physics was largely in providing an observer-independent account (even relativity, though it says measurements differ by frame, has invariant laws that all frames agree on). Quantum mechanics, however, introduced the observer in a way that has never been fully banished (despite efforts to decohere or hidden-variable it away). The Frauchiger–Renner paradox may indicate that this was not an accident or a failing of our formulations, but an inherent feature: perhaps any theory that aims to be complete must include the observer as part of the system (self-reference), and that will inevitably limit the objectivity.

This suggests there may be structural limits to knowledge and shared reality that are only now becoming apparent. Philosophers talk about unknown unknowns – things we don’t even have a concept for yet. FR might be scratching the surface of an unknown unknown: maybe a future theory (combining quantum mechanics and whatever principle of self-reference or consciousness is needed) will reveal a new principle, akin in impact to how relativity revealed the invariance of the speed of light or the equivalence of mass and energy. What could such a principle be? Some possibilities:

• A new logic of events: Perhaps classical binary logic (either the coin is heads or tails) doesn’t hold at the fundamental level when considering multiple observers. There might be a consistent “quantum logic” or type of temporal logic that avoids contradiction by not allowing certain inference chains. Indeed, some analysts have recast FR in terms of logical structures and identified the precise inference step that fails. Maybe in a deeper theory, the concept of a global truth value for an unobserved event is as nonsensical as asking “what is the color of an electron?”.
• A new principle of perspectival invariance: The opposite of usual invariants; maybe a principle that physics should only deal in quantities that all observers can in principle agree on (through communication). If something is not communicable without disturbance (like a quantum phase), then it should not be considered a “reality” in the theory, but only a potentiality. In other words, codify Bohr’s intuition about only talking about classical outcomes. This might seem like just the Copenhagen interpretation restated, but it could be sharpened into a principle that constraints theories (for example, forbidding certain types of superobserver reasoning).
• A merging of information theory and ontology: Possibly the idea that information is fundamental will be taken one step further. We might come to say that “reality = information for an observer,” period. This is reminiscent of Wheeler’s “it from bit” and also of quantum Bayesian ideas. If that became a formal principle, physics might shift to describing the transformation of information between systems (the selves being information-processing agents). Already, quantum mechanics can be cast in terms of information (qubits, entropies). But bridging to the “self” might require identifying what kind of information integration constitutes an observer that can have a viewpoint. (This is where IIT might contribute: it says what kind of physical system has a first-person perspective – one with high Φ. If that was integrated into physics, we’d know which subsystems count as “observers” dynamically.)
• No-go theorems of knowledge: FR is essentially a no-go theorem. It might join things like Bell’s theorem and Kochen-Specker theorem as clues that classical assumptions fail. Bell’s theorem showed you can’t have local hidden variables – a hint that locality or realism must give. Kochen-Specker showed you can’t assign definite values to all quantum observables at once – context matters. FR shows you can’t have observers all applying QM in one world and not hit a contradiction – perhaps the hint is that certain combinations of knowledge are forbidden. Could it be pointing at a more general principle about the limits of self-reference in physical systems? Gödel’s incompleteness theorem in math showed that any formal system of a certain power can’t be both complete and consistent – there are true statements it can’t prove. By analogy, maybe any physical theory that allows observers to reason about each other can’t be both universally valid and non-contradictory in a single world. That’s essentially FR’s conclusion in formal terms. This might be a fundamental limit like Gödel’s – not a failing to overcome, but a feature of reality: there will always be an “incompleteness” when trying to have a third-person view of a first-person experience. We might have just stumbled on the physical expression of that.

In plainer terms, FR paradox underscores how the notion of a perfectly objective reality accessible to all may be an illusion – an approximation that works only when quantum effects are small or observers aren’t entangled. In daily life, we share a stable classical reality, so it seems objective. But at a deeper level, that objectivity might break down. This is reminiscent of how classical determinism breaks down into quantum indeterminism, or how continuity breaks into quanta. Perhaps objectivity itself is emergent, not fundamental.

If objectivity is emergent, then fundamentally reality might be an amalgam of many “views.” The phrase “construction of the self” doesn’t mean each of us whimsically makes the world, but that the world as it fundamentally is might be more like a collage of perspectives with no single unifying view except at emergent levels. This is a hard idea to stomach – it goes against the dream of a Theory of Everything that is from God’s perspective. But maybe the Theory of Everything will actually say “there is no single everything – only relations.” This would mirror a move in 20th century philosophy away from absolutes toward relations (as in process philosophy, or some interpretations of quantum mechanics as we’ve seen).

For consciousness studies, this could mean physics will not be able to ignore the phenomenon of the first-person perspective forever. Already, discussions of quantum awareness or theories like IIT hooking into physics show a potential convergence of fields. Should a theory unify quantum mechanics with a theory of consciousness (even if consciousness just acts as a rule triggering collapse, etc.), it would be revolutionary – fulfilling in a way Wheeler’s vision of unifying the “observer” with the “observed” in a fundamental theory.

However, we should also caution: It’s possible that the resolution of FR paradox is simply to accept many-worlds or Bohm, in which case one could say “Reality is not constructed by the self; instead, reality is a vast complex entity (multiverse or hidden variable tapestry) and each self only sees a slice of it.” In that scenario, the self doesn’t construct reality, it selects or navigates a piece of the pre-existing reality. That’s a more realist stance. But even then, the effective reality for that self is, in practice, constructed by their vantage. Many-worlds is an interesting case: it is completely objective (wavefunction of universe just evolves), yet no single observer ever experiences that full objectivity. They always see a branch. So one could argue that for practical purposes, each observer still lives in a self-constructed narrative (the branch they happen to inhabit), and the full wavefunction is a Platonic ideal they never access directly. This is almost like a compromise between idealism and realism: the wavefunction (real) plays the role of the noumenal world, and each branch (experience) is the phenomenon.

Bohmian mechanics does give a single actual history (positions of all particles over time) that objectively exists. If that turned out to be correct, one might say the paradox is resolved because one of the assumptions (maybe consistency or quantum universal validity) is bypassed – Bohm’s theory has a nonlocal mechanism that ensures consistency. In Bohm’s theory, reality is not constructed by the self; rather the self is just one more objectively evolving entity (though Bohm himself entertained ideas of a cosmic mind as well in later writings – there was a bit of mysticism creeping in).

Overall, the trend in mainstream quantum foundations is towards acknowledging observer-dependence as possibly fundamental. Zeilinger (a leader in quantum information, Nobel 2022) often said “In the quantum world, observer-independent facts may simply not exist.” This was in context of Bell experiments and the recent no-go theorems that extended Wigner’s friend (like a theorem by Brukner’s group in 2018 showing “no observer-independent quantum facts” if quantum mechanics holds and certain assumptions like locality hold). Those results, along with FR, form a kind of cumulative case that we must radically revisit how we define reality in physics.

Conclusion

In addressing “Is Reality a Construction of the Self?” through the Frauchiger–Renner paradox, we have traversed quantum mechanics, logic, and centuries of philosophy. It is fitting now to consolidate our findings and provide a coherent answer.

The Frauchiger–Renner paradox has served as a concrete catalyst for our inquiry. By considering two observers reasoning about each other with quantum theory, it forced a seemingly impossible situation: consistent reasoning led to inconsistent realities (one observer deducing “X” and another deducing “not X” with certainty) (New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong | Quanta Magazine). The resolution, as we discussed, lies in abandoning at least one classical assumption – most naturally, the assumption of a single, observer-independent reality that all observers share at all times (Wigner's friend - Wikipedia). What remains is a picture in which each observer has their own “reality” (their own set of facts), and only when they interact can those realities be compared and brought into alignment (and even then, quantum theory limits how much alignment is possible). This is a striking departure from the classical worldview, but it is strongly supported by relational interpretations and by the empirical tests of Wigner’s-friend-like scenarios ([1902.05080] Experimental test of local observer-independence).

So, is reality a construction of the self? If by “reality” we mean the universe of experiences and facts that an observer can verify, then yes, to a significant extent reality is constructed (or at least selected) by the self. Quantum mechanics in the FR paradox shows that what is an absolute fact for one agent may not be for another until a connection (observation/interaction) is made ([1902.07139] Relational analysis of the Frauchiger--Renner paradox and interaction-free detection of records from the past). Reality for that agent was constructed through their measurement (the classic Copenhagen notion of “the wavefunction collapses” can be seen as the observer’s act creating the fact). This doesn’t mean the physical world is arbitrary or that one can will anything into being – the structure of the world and the Hamiltonian dynamics constrain what can happen. But within those constraints, the observer’s actions (choices of measurement) and the mere act of observation do affect which aspect of reality comes to the fore.

Our interdisciplinary exploration buttresses this viewpoint. Phenomenology taught us that the world of our experience is inseparable from consciousness and perspective (30 Best Edmund Husserl Quotes With Image | Bookey). Quantum mechanics, through FR, gives a rigorous example of a world (the lab states, qubits, etc.) that has different states relative to different observers (Relational quantum mechanics - Wikipedia). These are two sides of the same coin: one philosophical, one physical, both saying the observer and the observed form a unity. As Merleau-Ponty insightfully noted, the naive belief in one single world accessible to all is an oversimplification – each of us is limited to our view (Maurice Merleau-Ponty Quotes (Author of Phenomenology of Perception)). FR shows that in the microscopic realm, one cannot consistently pretend all those views are one and the same; one must instead treat them relationally.

From an epistemological stance, Kant and Putnam would likely nod at the FR outcome – it underscores the idea that we cannot step out of our human (or agent-specific) perspective to see “things-in-themselves” free of observation ([DOC] Kant and Putnam: Internal Realism and Truth - PhilArchive). The best we can do is communicate and find common ground, which is exactly what classical physics allowed (since we all ultimately observe classical pointers and can agree on them). But in the quantum regime, even communication has limits – you cannot tell Wigner your result without changing something if he hasn’t measured yet. So, there are fundamental limits on shared knowledge.

In metaphysical terms, interpretations like QBism and RQM explicitly embrace the idea that reality is personal or relative. QBism would answer our question by saying: Reality (or at least the meaningful reality we talk about in science) is a construction of the believing agent. The quantum state is an agent’s construct, and outcomes are the agent’s personal experience ([2008.03572] Respecting One's Fellow: QBism's Analysis of Wigner's Friend). Relational QM would answer: Reality is not an absolute structure; it’s a web of interrelated observations. Take away the observers (the relations) and meaning disappears. These are not far from saying reality is in the eye of the beholder – albeit constrained by consistency with others.

What about the role of consciousness and the self per se? While the paradox does not require consciousness to be formulated, the concept of “the self” in the broader question invites us to consider consciousness. Here we find an interesting possibility: the self that constructs reality might ultimately refer to conscious awareness. If someday it is confirmed that consciousness has a physical effect (e.g. causing collapse) (), then the self’s role in constructing reality becomes literal – the mind would help choose outcomes. Even if not, at least the self constructs reality in the sense of selecting the subset of facts that enter their experience. Integrated Information Theory and other frameworks suggest a future where physics and consciousness might meet, which could deepen our understanding of what an “observer” really is. If high integrated information is needed to have a definite perspective, then perhaps only systems above a certain complexity truly “create reality” in the sense of experiencing definite outcomes, whereas simpler systems (photodiodes, etc.) just spread entanglement without an experienced reality. This is speculative, but it hints that the emergence of a “self” (a bounded conscious perspective) might correspond to the emergence of a classical reality for that self. That is essentially von Neumann’s chain: at some juncture – perhaps the brain – the quantum possibilities reduce to one actuality.

One might ask: if reality is a construction of selves, how do multiple selves agree on anything? The answer is that we only agree on the intersection of our experiences after communication, and quantum mechanics ensures that intersection is generally classical (as per quantum Darwinism – what gets imprinted in the environment is what multiple observers can agree upon). Thus our shared reality is like the common part of many individual constructions. It’s robust for everyday objects (hence science and engineering work fine without worrying about who observes what), but it breaks down in extreme cases like Wigner’s friend where observers are isolated from each other.

In closing, the Frauchiger–Renner paradox does not imply that “nothing is real unless I observe it” in a solipsistic or trivial way. Rather, it implies a more nuanced truth: reality has a participatory, pluralistic character. Each observer participates in reality by instantiating facts, and reality in total may well be “a spectrum of viewpoints rather than a unitary whole.” This aligns with relational ontologies in modern physics and with long-standing philosophical positions that the mind and world are a continuum, not a strict subject-object dualism where the object is entirely independent.

Thus, to the thesis question, we answer: Yes – reality (as we can meaningfully define it) is to a considerable degree a construction of the self, or more precisely, a co-construction between the self and whatever is being observed. The Frauchiger–Renner paradox reinforces that any attempt to remove the self (the observer’s perspective) from the account of reality leads to contradictions, implying that the self is an integral element of reality’s fabric and cannot be treated as a neutral bystander. This fundamentally perspectival nature of reality may well be one of the “unknown unknowns” that physics is starting to unwrap – a frontier where questions about knowledge, observation, and existence converge.

The implications of this view are profound. It suggests a new epistemic humility: there may be no final “view from nowhere” theory of everything – or if there is, it might have to encode the fact that it appears different to different “insiders.” It also humanizes our scientific worldview: observers (perhaps conscious ones) are not incidental; they are central. Some, like Wheeler and Linde, even imagine that without observers the universe is “an unfinished sketch” (John Wheeler’s Participatory Universe) (John Wheeler’s Participatory Universe). Whether or not one goes so far, it’s clear that the classical ideal of objective reality must give way to a richer conception wherein reality and the act of observation are entwined.

In the end, we arrive at a perspective that is in harmony with both modern physics and deep philosophy: the world is not a ready-made object that the self observes, but a tapestry that is woven through the act of observation itself. Reality happens at the interface between self and world. To exist (in the sense of being a concrete fact) is to exist for some observer or community of observers. This does not diminish the existence of the world; rather, it elevates the role of the self in the cosmos. As the physicist John Wheeler succinctly put it, we are tiny parts of the universe that have become self-aware and now participate in its unfolding – “We are participants in bringing into being not only the near and here, but the far away and long ago.” (John Wheeler’s Participatory Universe)

The Frauchiger–Renner paradox, by challenging the consistency of a “view from outside,” ultimately supports the view that every view is from inside – inside a mind, inside a frame of reference, inside an interaction. Reality consists of these inside views, stitched together where they overlap. In that sense, reality is a construction (or reconstruction) of the self – not in a whimsical way, but in a fundamental, ontologically-necessary way.

References

• Frauchiger, D. & Renner, R. (2018). Quantum theory cannot consistently describe the use of itself. Nature Communications 9:3711. (Wigner's friend - Wikipedia) (Wigner's friend - Wikipedia)
• Brukner, Č. (2018). A no-go theorem for observer-independent facts. Entropy, 20(5), 350. (Related to Wigner’s friend and extended scenarios) ([1902.05080] Experimental test of local observer-independence).
• Proietti, M. et al. (2019). Experimental test of local observer-independence. Science Advances, 5(9): eaaw9832. (Demonstrated violation of assumptions, implying observer-dependent interpretation of quantum theory) ([1902.05080] Experimental test of local observer-independence).
• Waaijer, M. & Van Neerven, J. (2021). Relational analysis of the Frauchiger–Renner paradox. Foundations of Physics, 51(2):45. (Shows FR paradox disappears if one observer’s certainty isn’t taken as another’s without communication) ([1902.07139] Relational analysis of the Frauchiger--Renner paradox and interaction-free detection of records from the past).
• Wigner, E. (1961). Remarks on the mind-body question. In The Scientist Speculates (ed. I. J. Good). (Origin of Wigner’s friend thought experiment, suggesting consciousness causes collapse) (This Twist on Schrödinger's Cat Paradox Has Major Implications for Quantum Theory | Scientific American).
• Wheeler, J.A. (1983). Law Without Law. In Quantum Theory and Measurement (eds. J.A. Wheeler & W.H. Zurek). (Introduced “participatory universe” idea: “no phenomenon is a real phenomenon until it is an observed phenomenon”) (John Wheeler’s Participatory Universe).
• Linde, A. (1998). Universe, Life, Consciousness. In Science and Ultimate Reality: Quantum Theory, Cosmology and Complexity (J.D. Barrow et al., eds.). (Quote: “The universe and the observer exist as a pair.”) (John Wheeler’s Participatory Universe).
• Husserl, E. (1931). Ideas I (trans. W.R. Boyce Gibson). (Phenomenological argument that the world of experience is constituted by consciousness; “the physical world is merely a representation of our conscious experiences” interpreted in (30 Best Edmund Husserl Quotes With Image | Bookey).)
• Merleau-Ponty, M. (1945). Phenomenology of Perception. (Emphasizes embodied perspective; quote about the child’s openness and lack of multiple viewpoints (Maurice Merleau-Ponty Quotes (Author of Phenomenology of Perception)).)
• Kant, I. (1781). Critique of Pure Reason. (Proposed that we never know things-in-themselves, only phenomena shaped by our forms of intuition and understanding) ([DOC] Kant and Putnam: Internal Realism and Truth - PhilArchive).
• Putnam, H. (1981). Reason, Truth and History. (Putnam’s internal realism: rejects God’s-eye view, truth is model-dependent) ([DOC] Kant and Putnam: Internal Realism and Truth - PhilArchive).
• Fuchs, C. et al. (2014). An introduction to QBism with an application to the locality of quantum mechanics. American Journal of Physics, 82(8): 749-754. (Explains the QBist view: quantum probabilities are personal judgments, quantum states are information, resolves Wigner’s friend by each agent having their own state) ([2008.03572] Respecting One's Fellow: QBism's Analysis of Wigner's Friend) ([2008.03572] Respecting One's Fellow: QBism's Analysis of Wigner's Friend).
• Rovelli, C. (1996). Relational quantum mechanics. International Journal of Theoretical Physics, 35(8): 1637-1678. (Original RQM paper: “Quantum mechanics is a theory about the physical description of physical systems relative to other systems” (Relational quantum mechanics - Wikipedia); no absolute state, facts are relative (Relational quantum mechanics - Wikipedia).)
• Chalmers, D.J. & McQueen, K.J. (2022). Consciousness and the collapse of the wave function. In S. Gao (ed.), Consciousness and Quantum Mechanics (OUP). (Develops a theory linking IIT (Integrated Information) to collapse dynamics; suggests consciousness could enforce single-world outcomes) ().
• Sudbery, A. (2017). Single-world theory of the extended Wigner’s friend experiment. Foundations of Physics, 47(5): 658-669. (One of several responses to FR paradox analyzing assumptions – argues for many-worlds or modifications.)
• Healey, R. (2018). Quantum theory and the limits of objectivity. Foundations of Physics, 48(11): 1568-1589. (Discusses no-go theorems from a philosophical standpoint, aligning with participatory reality; suggests dropping assumption of observer-independent facts.)

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OK, let me see. I’m piecing together how friends in Alice and Bob's labs prep and measure a quantum coin toss, leading to confusing conclusions about the coin's outcome.

OK, let me see. I'm considering how reality might be shaped by the self, exploring quantum mechanics, participatory realism, and evolving theories like Integrated Information Theory.

Read wired.com

ChatGPT

I'm mapping out images, considering conceptual figures, a coin image, or a Wigner's friend diagram. Creating conceptual figures might be best, respecting OpenAI's embed_image rules.

Searched for Wigner's friend cartoon thought experiment

Read physicsworld.com

ChatGPT

I’m assessing an image on iStock, likely a drawing or stock representation, potentially unavailable without membership.

Read more from physicsworld.com

ChatGPT

The image portrays swirling blue and red dots with an opening door of light, symbolizing separate subjective realities. The caption hints at Wigner and his friend's differing yet valid outcomes.

Read informationphilosopher.com

ChatGPT

Considering integrating an image of Wigner's friend. Noticing the abstract from "Physics World" as an introduction header.

Read scientificamerican.com

ChatGPT

It's possible that the image in the SciAm is a generic one, but it could also potentially illustrate Schrödinger's cat.

Read static.scientificamerican.com

ChatGPT

I'm examining a haunting hand silhouette with light cables, hinting at entanglement or consciousness. It’s an intriguing visualization from Getty.

Read ultracold.substack.com

Searched for Wigner's friend cartoon imageChatGPT

Crafting sections with headings, bullet lists, and formal analysis. Pulling in key literature and ideas from thinkers like Kant, Husserl, and Proietti to form a cohesive narrative.

Read philarchive.org

ChatGPT

I'm brainstorming how Kant and Putnam link reality and conceptual perspective. Meanwhile, Chalmers and McQueen explore consciousness and quantum events. Exploring idealism with Wheeler and Linde follows.