# The Common Room Argument ## Intro No one has ever had anyone else's experience. Your pain is yours. The red you see is seen from inside your head, and no one can step in and check it. Each of us lives in a private room. And yet we all meet in the same place. Billions of people, each locked in a private room, look out and describe one world: the same mountain, the same sunrise, the same reading on the thermometer. Instruments built in different countries by people who never met agree to many decimal places. Somehow the private rooms all open onto one common room. That is not as obvious as it sounds. We cannot prove our senses are reliable without using our senses. And at the deepest level, physics itself treats a shared, observer-independent world as something it has to explain, not something it can take for granted. The Common Room Argument says the fit between private minds, trustworthy senses and a public world makes the most sense if one Author made all three for each other. "He that planted the ear, shall he not hear? He that formed the eye, shall he not see?" ([Psalm 94:9](/codex/psalms-94-9/), ASV). ## In full The Common Room Argument is a likelihood argument from the passage between private experience and public reality. Its explanandum is a conjunction: conscious experience is irreducibly first-personal (Nagel); private perspectives, human and instrumental, nonetheless converge on a single public world with extraordinary precision; the reliability of the senses that mediate this convergence cannot be established without epistemic circularity (Alston, following Reid); and quantum theory does not guarantee observer-independent shared facts but must explain them, for instance as the redundant broadcasting of pointer states into the environment (quantum Darwinism), while extended Wigner's friend no-go theorems show that some natural assumptions about absolute observed events cannot all be kept. A deductive spine (P1 to P6) argues that a world in which private minds, circularly justified senses and a structure that broadcasts its states redundantly fit together to form a common world is far more expected if one Author made senses, minds and world for one another than on naturalism, where their fit is underwritten only by selection for fitness, which does not by itself select for truth. The strongest rival, the common-cause explanation of agreement joined to evolutionary epistemology, is answered by showing that it presupposes the reliability in question. The conclusion is confirmatory and modest; the quantum strand is interpretation-dependent and is weighted lightly. ## Format note This is a **braided case**, the house format for new [Ris3n Arguments](/codex/ris3n-arguments/): a valid spine, each premise with independent strands, a knot, a likelihood ledger and a defeater gate. It braids four fields. **Sense data** contributes the privacy of experience and the circularity of checking the senses. **Reality** contributes the fact of one public world that private minds and instruments agree on. **Quantum physics** contributes the finding that shared objectivity is something physics has to earn, and that it rests on specific features of the world's structure. **Philosophy** contributes Reid and Alston on trust in the senses, Davidson on triangulation, and the comparison of rival accounts. ## The spine | # | Premise | |---|---| | **P1** | **Privacy.** Each conscious subject's experience is first-personal: no one can have, or directly inspect, another's experience. | | **P2** | **Publicity.** Nonetheless, billions of private perspectives, and independently built instruments, converge on one public world with great precision. | | **P3** | **Circularity.** The reliability of the senses that deliver this convergence cannot be established without relying on those senses. | | **P4** | **Earned objectivity.** Fundamental physics does not guarantee observer-independent shared facts; one leading account (quantum Darwinism) explains them by specific structural features of the world, and extended Wigner's friend theorems show they cannot be taken for granted in every interpretation. | | **P5** | **The hypotheses.** If one Author made minds, senses and world for each other, the meeting of private minds in a public world through reliable senses and a world built to broadcast its states is expected. On naturalism, minds, senses and the world's structure have no common intending cause, and selection guarantees only that senses serve fitness. | | **P6** | **The likelihood principle.** Evidence far more expected on one hypothesis than on another confirms the first over the second. | | **C** | **Therefore the common world shared by private minds confirms theism over naturalism.** | **Validity.** P1 to P4 establish the datum: private minds, using senses they cannot independently certify, meet in a public world whose objectivity is a structural achievement rather than a given. P5 says this is far more expected on theism. P6 converts that into confirmation. The form is a likelihood comparison closed by modus ponens. **Strength of the conclusion.** Confirmatory and modest. The argument does not claim that naturalism makes the shared world impossible, nor that physics implies God. It claims the overall fit is better expected on a common Author. ## P1, Privacy ### Inductive strand 1. **The subjective point of view.** Thomas Nagel, "What Is It Like to Be a Bat?" (*Philosophical Review* 83, 1974), argued that conscious experience has a subjective character tied to a single point of view. See [Thomas Nagel](/codex/thomas-nagel/). 2. **The private-language debate.** Ludwig Wittgenstein's *Philosophical Investigations* (1953, sections 243 and following) attacked the idea of a language whose words refer to what only the speaker can know. Whatever its outcome, the debate presupposes that experience itself is private; the dispute is over whether meaning can be. 3. **The secondary qualities.** Since Galileo's *The Assayer* (1623), science has distinguished measurable quantities from the qualities that exist only as experienced, such as colour and taste. ### Abductive strand | Explanation of P1's data | Explanatory power | Scope | Simplicity | Ad hoc? | |---|---|---|---|---| | Persons are real, individual centres of awareness (the image of a personal God) | Explains first-personal privacy | All conscious subjects | One posit | No | | Physicalism: experience is a brain state, private only in the way your stomach is private | Explains the correlation | Leaves the subjective character unexplained | Simple | No, but owes the gap | ### Convergence Philosophy of mind (Nagel), philosophy of language (Wittgenstein) and the history of science (Galileo's split between quantities and qualities) reach P1. See [Argument from Consciousness](/codex/argument-from-consciousness/). ### Objections and rebuttals 1. *"Wittgenstein refuted privacy."* **Rebuttal.** He argued against a private language, not against private experience. The common reading is that public language for inner states is possible because there are public criteria, which is the bridge P2 describes. ## P2, Publicity ### Inductive strand 1. **Agreement among instruments.** Independent laboratories using different apparatus measure the fundamental constants to agreement within stated uncertainties, which is why reference values can be set internationally. 2. **Agreement among persons.** Ordinary life, courts and science depend on independent observers agreeing about what happened. The resurrection appearances were offered to the early church on exactly these terms: "he appeared to above five hundred brethren at once" ([1 Corinthians 15:6](/codex/1-corinthians-15-6/), ASV). 3. **Triangulation.** Donald Davidson, "Three Varieties of Knowledge" (in A. Phillips Griffiths, ed., *A. J. Ayer: Memorial Essays*, Cambridge, 1991), argued that objective thought requires a triangle of two communicating creatures and a shared world. ### Abductive strand | Explanation of P2's data | Explanatory power | Scope | Simplicity | Ad hoc? | |---|---|---|---|---| | One real world, made knowable to minds made to know it | Explains agreement across persons, cultures and instruments | Wide | One posit | No | | Common external cause plus similar senses (Bertrand Russell, *The Problems of Philosophy*, 1912, chapter 2) | Explains agreement well | Presupposes the senses are reliable | Simple | No, but see P3 | | Shared species-specific interface (Hoffman) | Explains human agreement | Weak on agreement between human senses and non-human instruments about quantities | Moderate | Partly | ### Convergence Metrology, legal testimony, philosophy of language (Davidson) and the realist tradition from Reid to Russell all reach P2. Even sceptics act on it. ### Objections and rebuttals 1. *"Agreement could be a shared illusion."* **Rebuttal.** Then instruments built on different physical principles would be sharing the illusion too. Shared illusion explains less as the independence of the witnesses grows. ## P3, Circularity ### Inductive strand 1. **Alston's result.** William P. Alston, *The Reliability of Sense Perception* (Cornell, 1993), examined the main attempts to show that sense perception is reliable and argued that every successful one relies, at some point, on premises known by perception. The circularity is not a defect of particular arguments but of the project. 2. **Reid's same shop.** [David Hume](/codex/david-hume/)'s scepticism drew this reply from Thomas Reid, *An Inquiry into the Human Mind* (1764), chapter 6, section 20: why trust the faculty of reason more than that of perception, "they came both out of the same shop, and were made by the same artist; and if he puts one piece of false ware into my hands, what should hinder him from putting another?" 3. **Common sense.** The Moorean response to scepticism takes the reliability of perception as more certain than any sceptical premise. See [Mooreanism](/codex/mooreanism/) and [Skepticism](/codex/skepticism/). ### Abductive strand | Explanation of P3's data | Explanatory power | Scope | Simplicity | Ad hoc? | |---|---|---|---|---| | The senses are reliable because they were made by a trustworthy Maker; our trust is properly basic | Explains why the trust is rational though unprovable from within | All faculties | One posit | No | | Reliabilism without a designer: the senses are reliable as a matter of fact, whether or not we can show it | Explains warrant if true | Gives no reason to expect reliability | Simple | No, but silent on why | | Scepticism: we do not know the senses are reliable | Explains the circularity | Unlivable and self-undermining | Simple | No | ### Convergence Reid in the eighteenth century, Alston in the twentieth, and contemporary [Reformed Epistemology](/codex/reformed-epistemology/) reach P3 and conclude that trust in the senses is rational without independent proof. Naturalist reliabilists accept the circularity point and disagree about what follows. ### Objections and rebuttals 1. *"Every belief system is circular at the base, theism included."* **Rebuttal.** Granted, and the argument does not claim to escape the circle. It asks which worldview gives reason to expect that the circle is a reliable one. Theism has a Maker who intends reliability; naturalism has selection, which intends nothing and rewards fitness. See [Argument from the Reliability of Reason](/codex/argument-from-the-reliability-of-reason/). ## P4, Earned objectivity ### Inductive strand 1. **Objectivity from redundancy.** Harold Ollivier, David Poulin and Wojciech Zurek, "Objective Properties from Subjective Quantum States: Environment as a Witness" (*Physical Review Letters* 93, 2004), and Zurek, "Quantum Darwinism" (*Nature Physics* 5, 2009), propose that the classical world we agree on arises because the environment (light, air molecules) makes many redundant copies of information about a system's preferred states. Independent observers who each intercept a small fragment of the environment find out the same thing, and so agree. Objectivity, on this account, is a structural achievement of the world, not an axiom of the theory. 2. **The Wigner's friend no-go theorems.** Daniela Frauchiger and Renato Renner, "Quantum Theory Cannot Consistently Describe the Use of Itself" (*Nature Communications* 9, 2018), and Kok-Wei Bong and colleagues, "A Strong No-Go Theorem on the Wigner's Friend Paradox" (*Nature Physics* 16, 2020), show that in scenarios where one observer measures another observer's laboratory, a set of natural assumptions, including that observed events are absolute rather than relative to the observer, cannot all hold if quantum predictions are right. Massimiliano Proietti and colleagues (*Science Advances* 5, 2019) reported a small-scale experimental test. 3. **The interpretations differ.** Many-worlds, Bohmian, collapse, relational and QBist interpretations respond to these results differently; some give up absolute observed events, others give up other assumptions. Nothing here shows that consciousness affects physical reality, and the argument makes no such claim. ### Abductive strand | Explanation of P4's data | Explanatory power | Scope | Simplicity | Ad hoc? | |---|---|---|---|---| | The world was made with a structure that broadcasts its states redundantly, so that many knowers can share it | Explains why objectivity is achieved rather than given, and why it holds where knowers live | The macroscopic world of observers | One posit | No | | Quantum Darwinism as brute physics | Explains the mechanism fully | Wide | Simple | No; it explains how, not why the world is structured so | | Interpretations that make facts observer-relative | Accommodate the no-go results | Wide | Varies | No; but they make the common room less guaranteed, not more | ### Convergence Quantum foundations (Zurek's programme, the Wigner's friend theorems), experimental quantum optics (Proietti and colleagues) and philosophy of physics reach P4. Their convergence is negative and structural: shared objectivity is not free. ### Objections and rebuttals 1. *"This is quantum mysticism."* **Rebuttal.** No. The argument does not say observers create reality, or that God collapses wavefunctions. It uses only the mainstream finding that classical objectivity needs explaining, and the mainstream explanation, which appeals to the structure of the environment. 2. *"Quantum Darwinism explains objectivity naturalistically."* **Rebuttal.** It explains the mechanism, and the argument welcomes it. The question is why the world has a structure that turns private interactions into public facts. The ledger rates this row lightly for that reason. ## P5, The hypotheses ### Inductive strand 1. **Theism.** On Christian theism one God formed the eye and the ear ([Psalm 94:9](/codex/psalms-94-9/); [Proverbs 20:12](/codex/proverbs-20-12/)), made a world that shows his works ([Romans 1:20](/codex/romans-1-20/); [Psalm 104:24](/codex/psalms-104-24/)), and made human beings in his image to share a common life ([Acts 17:26-28](/codex/acts-17-26-28/)). Private minds, reliable senses and a public world have one Author, so their fit is expected. 2. **Naturalism.** On naturalism the senses are shaped by selection for fitness, the world's structure is set by physics without reference to knowers, and minds arise from both. Donald Hoffman and colleagues argue that selection need not tune perception to truth at all ("The Interface Theory of Perception," *Psychonomic Bulletin and Review* 22, 2015); Alvin Plantinga, *Where the Conflict Really Lies* (Oxford, 2011), argues that naturalism plus evolution gives no reason to trust our faculties. See [Donald Hoffman](/codex/donald-hoffman/) and [Fitness Beats Truth Argument](/codex/fitness-beats-truth-argument/). ### Abductive strand The naturalist's best answer is that agreement among observers is explained by a common external cause acting on similar senses. That is the defeater gate. ### Convergence Reidian epistemology, Reformed epistemology, Plantinga's evolutionary argument and Hoffman's interface theory (from a non-theistic direction) converge on the claim that naturalism does not by itself predict truth-tracking senses. ### Objections and rebuttals 1. *"This is just the Argument from Perception again."* **Rebuttal.** No. The [Argument from Perception](/codex/argument-from-perception/) argues that perception's aboutness and capacity for error are not physical properties. This argument is about the passage from private to public: how many private perspectives, through uncheckable senses, meet in one world. ## P6, The likelihood principle ### Inductive strand The principle is standard in probability theory and scientific confirmation. ### Abductive strand Rejecting it would undercut the statistical reasoning by which independent measurements are combined. ### Convergence Bayesian and likelihoodist approaches agree on this comparative use. ### Objections and rebuttals 1. *"Priors decide."* **Rebuttal.** The ledger is prior-agnostic; see [Cumulative Case for Christian Theism](/codex/cumulative-case-for-christian-theism/). ## The knot The strands are independent: philosophy of mind (Nagel), philosophy of language (Wittgenstein, Davidson), epistemology (Reid, Alston, Plantinga), metrology and legal testimony, quantum foundations (Zurek, Frauchiger and Renner, Bong and colleagues) and cognitive science (Hoffman). Two overlaps are counted once: Alston and Reid make one point in two centuries, and Hoffman's and Plantinga's arguments share the claim that fitness need not track truth. P3 also overlaps the [Argument from the Reliability of Reason](/codex/argument-from-the-reliability-of-reason/); this page uses it only as one strand of a different datum. ## The ledger Prior-agnostic: the ledger asks only how expected each datum is under each hypothesis. The ratings are reasoned judgments from the sections above, not measurements. | Datum | How expected on theism | How expected on naturalism | Favours | Why | Independent? | |---|---|---|---|---|---| | Experience is private (P1) | High | Moderate | Theism, slightly | Overlaps the consciousness argument | Partly; counted lightly | | Private minds and instruments agree on one world (P2) | High | Moderate to high | Theism, slightly | Common cause explains it, given reliable senses | Yes | | Sense reliability cannot be shown non-circularly (P3) | High (trust is designed and basic) | Moderate | Theism, slightly | Naturalism can accept brute reliability | Yes | | Senses tuned to truth, not only fitness | High | Low to moderate (Hoffman, Plantinga) | Theism, modestly; contested | Disputed claim about selection | Partly overlaps P3 | | Objectivity is earned by world structure (P4) | Moderate to high | Moderate | Theism, slightly; interpretation-dependent | Quantum Darwinism gives a naturalistic mechanism | Yes | | The three fit together: private minds, uncheckable senses, a broadcasting world | High | Low to moderate | Theism, modestly | No common intending cause on naturalism | The conjunction | **Net.** This is a modest argument. No row is strong by itself, and the quantum row is light because the mechanism is naturalistic and the interpretations disagree. The weight sits on the conjunction: three independent things, private awareness, senses we cannot check, and a world built to be shared, all fit, and that fit is what one Author would produce. ## The defeater gate **The common cause.** The strongest objection is the classic realist inference joined to evolutionary epistemology. Bertrand Russell (*The Problems of Philosophy*, 1912, chapter 2) argued that the simplest explanation of our agreeing experiences is a common external world causing them. Add that natural selection built similar senses in all humans because organisms whose senses tracked their surroundings survived. Then agreement is explained by a common cause acting on similar instruments, and no Author is needed. The reply has three steps. 1. **The common cause presupposes reliability.** The inference to a common external world works only if our senses are reliable reporters of their causes. That is exactly what P3 says cannot be shown without using them. The naturalist is entitled to trust the senses; he is not entitled to say his worldview predicts their reliability. 2. **Selection predicts fitness, not truth.** On Hoffman's results, perception tuned only by selection is expected to track fitness payoffs, not the structure of the world. If he is right, the naturalist's story explains agreement in the interface, not access to a common reality. If he is wrong, the naturalist must still argue that fitness and truth coincide, which theism explains by a common Author. 3. **Physics does not hand over the common room for free.** At the quantum level, shared facts arise from a particular structure of the world. The naturalist can take that structure as brute. The theist expects it. What the gate concedes: the common-cause explanation is good, and theists use it too. The argument does not reject it. It claims the common cause, the reliable senses and the broadcasting world are best explained together. See [Argument from Reason](/codex/argument-from-reason/) and [Self-refutation](/codex/self-refutation/). ## Concessions - *Grant:* agreement is explained by a common external cause. *Now collect:* only if the senses are reliable, and reliability is the thing in question. - *Grant:* quantum Darwinism explains objectivity physically. *Now collect:* it explains how a world must be structured to be shared; it does not explain why ours is. - *Grant:* the argument is modest. *Now collect:* modest arguments add up, and this one draws on evidence no other argument in the codex uses. ## Cheatsheet **The 30-second version (read aloud).** Every person lives in a private room: no one has ever felt your pain or seen your red. Yet billions of private rooms all open onto one common room, the same world, measured the same by instruments built continents apart. We can't prove our senses are reliable without using them. And at the deepest level, physics has to work to explain how a shared world arises at all. Private minds, uncheckable senses, a world built to be shared: if one Maker made the eye, the ear and the world, that fit is what you'd expect. **Fast facts:** 1. Nagel (1974): experience has a subjective character tied to one point of view. 2. Alston (1993): every argument for the reliability of perception relies on perception. 3. Reid (1764): reason and perception "came both out of the same shop, and were made by the same artist." 4. Zurek (*Nature Physics*, 2009): shared classical facts arise from redundant records in the environment. 5. Bong et al. (*Nature Physics*, 2020): in Wigner's friend scenarios, natural assumptions about absolute observed events cannot all hold. **The closing line.** We each look out from a private window, and we all see the same garden, because the same gardener built the house. ## Cross-examination ### Round 1, The private room - **Q:** Have you ever had someone else's experience? - **If they say no:** then everything you know about the world came through a private window. How do you know the windows agree? ### Round 2, The senses - **Q:** Can you show your senses are reliable without using your senses? - **If they say no:** then your trust in them is basic. What, on your view, makes that trust reasonable rather than lucky? - **If they say science shows it:** science uses the senses. That is the circle. ### Round 3, The physics - **Q:** Does quantum theory simply guarantee that every observer's facts are absolute? - **If they say yes:** point to the Wigner's friend theorems and ask which assumption they give up. - **If they say no:** then the shared world is something the universe's structure achieves. Why is it structured that way? ### Dodge table | Dodge | What it concedes | Reply | |---|---|---| | "The world just causes our experiences." | A common cause | "That works only if the senses report causes truly, which is what we can't check." | | "Evolution made our senses reliable." | Reliability needs explaining | "Evolution selects for survival. Does survival require truth all the way to measuring constants?" | | "Quantum stuff is irrelevant." | The macroscopic world is shared | "It's relevant to why the macroscopic world is shareable at all." | | "Everyone's circular." | The circle is real | "Yes. The question is whose worldview gives reason to expect the circle to be reliable." | ## Live-cite kit **Scripture (ASV):** - [Psalm 94:9](/codex/psalms-94-9/): He that planted the ear, shall he not hear? He that formed the eye, shall he not see? ([Psalm 94:9](/codex/psalms-94-9/), ASV) - [Proverbs 20:12](/codex/proverbs-20-12/): The hearing ear, and the seeing eye, Jehovah hath made even both of them ([Proverbs 20:12](/codex/proverbs-20-12/), ASV) - [Romans 1:20](/codex/romans-1-20/): For the invisible things of him since the creation of the world are clearly seen, being perceived through the things that are made, even his everlasting power and divinity; that they may be without excuse ([Romans 1:20](/codex/romans-1-20/), ASV) - [1 John 1:1, 3](/codex/1-john-1-1-3/): That which was from the beginning, that which we have heard, that which we have seen with our eyes, that which we beheld, and our hands handled, concerning the Word of life ... that which we have seen and heard declare we unto you also, that ye also may have fellowship with us ([1 John 1:1, 3](/codex/1-john-1-1-3/), ASV) - [John 20:27](/codex/john-20-27/): Reach hither thy finger, and see my hands; and reach hither thy hand, and put it into my side: and be not faithless, but believing ([John 20:27](/codex/john-20-27/), ASV) **Scholarly:** - Thomas Reid, *An Inquiry into the Human Mind* (1764), 6.20: reason and perception "came both out of the same shop." - William P. Alston, *The Reliability of Sense Perception* (1993). - Wojciech H. Zurek, "Quantum Darwinism," *Nature Physics* 5 (2009). - Kok-Wei Bong et al., "A Strong No-Go Theorem on the Wigner's Friend Paradox," *Nature Physics* 16 (2020). **Aphorism:** "Many windows, one garden." ## Connection to Scripture - [Psalm 94:9](/codex/psalms-94-9/) and [Proverbs 20:12](/codex/proverbs-20-12/), the eye and the ear are made, and made by one who himself sees and hears. - [1 John 1:1-3](/codex/1-john-1-1-3/), the apostolic witness moves from private seeing and handling to shared fellowship: the common room is the church's starting point. - [John 20:27](/codex/john-20-27/) and [Luke 24:39](/codex/luke-24-39/), the risen Christ invites the senses to check: "handle me, and see." - [1 Corinthians 15:6](/codex/1-corinthians-15-6/), five hundred witnesses at once: publicity offered as evidence. - [Romans 1:20](/codex/romans-1-20/), creation perceived through the things that are made, a world built to be seen. ## Scholarship Published academic works this page draws on, each matched to a publisher, index or library catalog record. - William P. Alston, *The Reliability of Sense Perception* (Cornell University Press, 1993). [Open Library](https://openlibrary.org/works/OL108573W) - Kok-Wei Bong et al., "A strong no-go theorem on the Wigner’s friend paradox," *Nature Physics* 16 (2020). [doi:10.1038/s41567-020-0990-x](https://doi.org/10.1038/s41567-020-0990-x) - Daniela Frauchiger and Renato Renner, "Quantum theory cannot consistently describe the use of itself," *Nature Communications* 9 (2018). [doi:10.1038/s41467-018-05739-8](https://doi.org/10.1038/s41467-018-05739-8) [PubMed 30228272](https://pubmed.ncbi.nlm.nih.gov/30228272/) [open access](https://www.nature.com/articles/s41467-018-05739-8.pdf) - A. Phillips Griffiths, *A. J. Ayer: Memorial Essays* (Cambridge University Press, 1992). [doi:10.1017/cbo9780511628740](https://doi.org/10.1017/cbo9780511628740) - Donald D. Hoffman, Manish Singh and Chetan Prakash, "The Interface Theory of Perception," *Psychonomic Bulletin & Review* 22 (2015). [doi:10.3758/s13423-015-0890-8](https://doi.org/10.3758/s13423-015-0890-8) [PubMed 26384988](https://pubmed.ncbi.nlm.nih.gov/26384988/) [open access](https://link.springer.com/content/pdf/10.3758/s13423-015-0890-8.pdf) - Harold Ollivier, David Poulin and Wojciech H. Zurek, "Objective Properties from Subjective Quantum States: Environment as a Witness," *Physical Review Letters* 93 (2004). [doi:10.1103/physrevlett.93.220401](https://doi.org/10.1103/physrevlett.93.220401) [PubMed 15601069](https://pubmed.ncbi.nlm.nih.gov/15601069/) [open access](https://arxiv.org/pdf/quant-ph/0307229) - Alvin Plantinga, *Where the Conflict Really Lies* (2011). [Open Library](https://openlibrary.org/works/OL21776757W) - Massimiliano Proietti et al., "Experimental test of local observer independence," *Science Advances* 5 (2019). [doi:10.1126/sciadv.aaw9832](https://doi.org/10.1126/sciadv.aaw9832) [PubMed 31555731](https://pubmed.ncbi.nlm.nih.gov/31555731/) - Thomas Reid, *An inquiry into the human mind, on the principles of common sense* (Alexander Ewing, 1764). [doi:10.1037/11974-000](https://doi.org/10.1037/11974-000) - Ludwig Wittgenstein, *Philosophical investigations* (1953). [Open Library](https://openlibrary.org/works/OL20944636W) ## See also - [Ris3n Arguments](/codex/ris3n-arguments/), the hub of ris3n's original arguments - [Arguments](/codex/arguments/), the master index - [Argument from Perception](/codex/argument-from-perception/), perception's aboutness and capacity for error; this page is about the passage from private to public - [Argument from the Observer-Demand Convergence](/codex/argument-from-the-observer-demand-convergence/), a different use of quantum measurement, about the human need to be seen - [Fitness Beats Truth Argument](/codex/fitness-beats-truth-argument/) and [Donald Hoffman](/codex/donald-hoffman/), selection and truth - [Argument from the Reliability of Reason](/codex/argument-from-the-reliability-of-reason/) and [Argument from Reason](/codex/argument-from-reason/), the parity point - [Reformed Epistemology](/codex/reformed-epistemology/), trust in the faculties as properly basic - [Mooreanism](/codex/mooreanism/) and [Skepticism](/codex/skepticism/), the sceptical background - [Phenomenology of Perception](/codex/phenomenology-of-perception/), the structure of perceptual experience - [Argument from Consciousness](/codex/argument-from-consciousness/), the privacy of experience - [Argument from Intelligibility](/codex/argument-from-intelligibility/), a world built to be understood - [Cumulative Case for Christian Theism](/codex/cumulative-case-for-christian-theism/), where this argument contributes ## Common questions this page answers **Q: How do we know other people see the same world we do?** We cannot have their experiences, but independent observers and instruments agree about the world with great precision. The Common Room Argument asks why private minds, using senses no one can check from outside, end up sharing one public world, and argues that one Maker of minds, senses and world explains it best. **Q: Can you prove your senses are reliable?** Not without using them. The philosopher William Alston argued that every attempt to show sense perception is reliable relies on perception somewhere. Thomas Reid answered the sceptic by noting that reason and perception come from the same maker, so distrusting one while trusting the other is arbitrary. **Q: What is quantum Darwinism?** It is Wojciech Zurek's account of how the shared classical world emerges from quantum physics. The environment, such as light and air, makes many redundant copies of information about an object's stable states, so independent observers who each catch a small part of it learn the same thing and agree. **Q: What is the Wigner's friend paradox?** It is a thought experiment in which one observer measures a system inside a lab while another observer treats the whole lab, friend included, as a quantum system. Recent theorems show that several natural assumptions, including that every observed event is absolute, cannot all hold if quantum theory's predictions are right. Physicists disagree about which assumption to drop. **Q: Does quantum physics prove that consciousness creates reality?** No. This argument makes no such claim. It uses only the mainstream finding that a shared, observer-independent world is something physics has to explain, and it states the interpretations as interpretations. **Q: How is this different from the argument from perception?** The argument from perception says perception is about things and can be mistaken, which are not physical properties. The Common Room Argument is about how many private perspectives meet in one public world.