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When Everyone Knows That Everyone Knows...: Common Knowledge and the Science of Harmony, Hypocrisy and Outrage
As a cognitive scientist, the ultimate subject of Steven Pinker’s fascination is how we think about each other’s thoughts, ad infinitum. It sounds impossible, but Steven Pinker shows that we do it all the time. This awareness, which we experience as something that is public or “out there,” is called common knowledge, and it has a momentous impact on our social, political, and economic lives.
Common knowledge, Pinker shows, can make sense of many of life’s enigmas: financial bubbles and crashes, revolutions that come out of nowhere, the posturing and pretence of diplomacy, the eruption of social media shaming mobs and academic cancel culture, the awkwardness of a first date. But people also go to great lengths to avoid common knowledge—to ensure that even if everyone knows something, they can’t know that everyone else knows they know it. And so we get rituals like benign hypocrisy, veiled bribes and threats, sexual innuendo, and pretending not to see the elephant in the room.
In exploring the paradoxes of human behaviour, When Everyone Knows that Everyone Knows… invites us to understand the ways we try to get into each other’s heads, and the harmonies, hypocrisies, and outrages that result.
Common knowledge, Pinker shows, can make sense of many of life’s enigmas: financial bubbles and crashes, revolutions that come out of nowhere, the posturing and pretence of diplomacy, the eruption of social media shaming mobs and academic cancel culture, the awkwardness of a first date. But people also go to great lengths to avoid common knowledge—to ensure that even if everyone knows something, they can’t know that everyone else knows they know it. And so we get rituals like benign hypocrisy, veiled bribes and threats, sexual innuendo, and pretending not to see the elephant in the room.
In exploring the paradoxes of human behaviour, When Everyone Knows that Everyone Knows… invites us to understand the ways we try to get into each other’s heads, and the harmonies, hypocrisies, and outrages that result.
384 pages, Hardcover
First published September 23, 2025
About the author
Steven Pinker
80 books10.8k followersSteven Arthur Pinker is a prominent Canadian-American experimental psychologist, cognitive scientist, and author of popular science. Pinker is known for his wide-ranging explorations of human nature and its relevance to language, history, morality, politics, and everyday life. He conducts research on language and cognition, writes for publications such as the New York Times, Time, and The New Republic, and is the author of numerous books, including The Language Instinct, How the Mind Works, Words and Rules, The Blank Slate, The Stuff of Thought, The Better Angels of Our Nature, The Sense of Style, and most recently, Enlightenment Now: The Case for Reason, Science, Humanism, and Progress.
He was born in Canada and graduated from Montreal's Dawson College in 1973. He received a bachelor's degree in experimental psychology from McGill University in 1976, and then went on to earn his doctorate in the same discipline at Harvard in 1979. He did research at the Massachusetts Institute of Technology (MIT) for a year, then became an assistant professor at Harvard and then Stanford University. From 1982 until 2003, Pinker taught at the Department of Brain and Cognitive Sciences at MIT, and eventually became the director of the Center for Cognitive Neuroscience. (Except for a one-year sabbatical at the University of California, Santa Barbara in 1995-6.) As of 2008, he is the Johnstone Family Professor of Psychology at Harvard.
Pinker was named one of Time Magazine's 100 most influential people in the world in 2004 and one of Prospect and Foreign Policy's 100 top public intellectuals in 2005. He has also received honorary doctorates from the universities of Newcastle, Surrey, Tel Aviv, McGill, and the University of Tromsø, Norway. He was twice a finalist for the Pulitzer Prize, in 1998 and in 2003. In January 2005, Pinker defended Lawrence Summers, President of Harvard University, whose comments about the gender gap in mathematics and science angered much of the faculty. On May 13th 2006, Pinker received the American Humanist Association's Humanist of the Year award for his contributions to public understanding of human evolution.
In 2007, he was invited on The Colbert Report and asked under pressure to sum up how the brain works in five words – Pinker answered "Brain cells fire in patterns."
Pinker was born into the English-speaking Jewish community of Montreal. He has said, "I was never religious in the theological sense... I never outgrew my conversion to atheism at 13, but at various times was a serious cultural Jew." As a teenager, he says he considered himself an anarchist until he witnessed civil unrest following a police strike in 1969. His father, a trained lawyer, first worked as a traveling salesman, while his mother was first a home-maker then a guidance counselor and high-school vice-principal. He has two younger siblings. His brother is a policy analyst for the Canadian government. His sister, Susan Pinker, is a columnist for the Wall Street Journal and the author of The Sexual Paradox and The Village Effect.
Pinker married Nancy Etcoff in 1980 and they divorced 1992; he married Ilavenil Subbiah in 1995 and they too divorced. He is married to the novelist and philosopher Rebecca Goldstein, the author of 10 books and winner of the National Medal of the Humanities. He has no children.
His next book will take off from his research on "common knowledge" (knowing that everyone knows something). Its tentative title is: Don't Go There: Common Knowledge and the Science of Civility, Hypocrisy, Outrage, and Taboo.
He was born in Canada and graduated from Montreal's Dawson College in 1973. He received a bachelor's degree in experimental psychology from McGill University in 1976, and then went on to earn his doctorate in the same discipline at Harvard in 1979. He did research at the Massachusetts Institute of Technology (MIT) for a year, then became an assistant professor at Harvard and then Stanford University. From 1982 until 2003, Pinker taught at the Department of Brain and Cognitive Sciences at MIT, and eventually became the director of the Center for Cognitive Neuroscience. (Except for a one-year sabbatical at the University of California, Santa Barbara in 1995-6.) As of 2008, he is the Johnstone Family Professor of Psychology at Harvard.
Pinker was named one of Time Magazine's 100 most influential people in the world in 2004 and one of Prospect and Foreign Policy's 100 top public intellectuals in 2005. He has also received honorary doctorates from the universities of Newcastle, Surrey, Tel Aviv, McGill, and the University of Tromsø, Norway. He was twice a finalist for the Pulitzer Prize, in 1998 and in 2003. In January 2005, Pinker defended Lawrence Summers, President of Harvard University, whose comments about the gender gap in mathematics and science angered much of the faculty. On May 13th 2006, Pinker received the American Humanist Association's Humanist of the Year award for his contributions to public understanding of human evolution.
In 2007, he was invited on The Colbert Report and asked under pressure to sum up how the brain works in five words – Pinker answered "Brain cells fire in patterns."
Pinker was born into the English-speaking Jewish community of Montreal. He has said, "I was never religious in the theological sense... I never outgrew my conversion to atheism at 13, but at various times was a serious cultural Jew." As a teenager, he says he considered himself an anarchist until he witnessed civil unrest following a police strike in 1969. His father, a trained lawyer, first worked as a traveling salesman, while his mother was first a home-maker then a guidance counselor and high-school vice-principal. He has two younger siblings. His brother is a policy analyst for the Canadian government. His sister, Susan Pinker, is a columnist for the Wall Street Journal and the author of The Sexual Paradox and The Village Effect.
Pinker married Nancy Etcoff in 1980 and they divorced 1992; he married Ilavenil Subbiah in 1995 and they too divorced. He is married to the novelist and philosopher Rebecca Goldstein, the author of 10 books and winner of the National Medal of the Humanities. He has no children.
His next book will take off from his research on "common knowledge" (knowing that everyone knows something). Its tentative title is: Don't Go There: Common Knowledge and the Science of Civility, Hypocrisy, Outrage, and Taboo.
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July 18, 2025
Although this is likely a lesser work in the Pinker Pantheon, When Everyone Knows That Everyone Knows... cleverly examines of the oft overlooked concept of common knowledge.
Pinker is quite precise about what "common knowledge" is, stating it's a collective epistemic state that results only when A knows X, B knows X, A knows that B knows X, B knows that A knows X, and so on ad infinitum. Pinker boldly claims that this recursive form of social knowledge is the linchpin behind coordination, cooperation, and collective action - otherwise known as the things that make humans human.
Pinker positions his claim as consistent but more foundational than Yuval Noah Harari's in Sapiens, which presents the more widely shared thesis that "our world is built on fictions" specifically the power of belief in various human narratives, including the state, private property, currency, individual rights, etc, is the X-factor that explains human success. The Pinker-cum-Harari thesis, itself narrative, is complemented by more rigorous and scientific theories of human success that are in circulation that still slot fairly neatly into the same paradigm: Acemoglu & Robinson's Why Nations Fail, The Social Brain by Robin Dunbar, and Joseph Henrich's The Secret of Our Successs, and The Theory of Everyone by Michael Muthukrishna. I raise these other works to highlight just how complicated the story of human success is; there isn't a single book or scientific study that's likely to perfectly explain why we've come to the spot we're in today. Pinker himself doesn't invest too much in this narrative in his book yet it is the rationale for why he's assembled a whole book on a seeming mundane idea.
Extending the justification for his interest in common knowledge, Pinker runs through a number of coordination problems that humans face. The examples he provides are typically abstracted, drawing heavily from economics and geopolitics, specifically the sub-field of game theory: the Prisoners' Dilemma, the Stag Hunt, the Battle of the Sexes, Hawks and Doves, etc. These coordination problems inevitably prompt questions about how to resolve them, which allows Pinker to explain the mechanism by which common knowledge can emerge: common salience (a focal point), conspicuity, and recursive mentalizing. Common knowledge doesn't necessarily lead to positive outcome though. Its presence can cause malign coordination as well as beneficial coordination, triggering a number of reciprocal strategies from various parties in a coordination game. Pinker walks through examples of this including bank runs, financial market bubbles, and Keynesian beauty contests.
After exploring the role of common knowledge in abstracted scenarios, Pinker shifts to a focus on social relationships (perhaps the most important human coordination problem), describing the structure of different types of relationships (communal sharing, authority ranking, equality matching, and market pricing - derived from Alan Fiske's work), the mechanisms involved (namely symbolic communication) and the stakes (reputation). This rolls into how our physiology is enmeshed in these dynamics, specifically how conspicuous emotional expressions that generate common knowledge (laughing, crying, blushing, staring, glaring). It also flows into strategies we've deployed to avoid acknowledging common knowledge, such as innuendo and euphemisms, or preclude its development, censorship, cancellation, and strategic hypocrisy. Intriguingly, Pinker invests the entire final chapter defending Plato's concept of the Noble Lie (without using that terminology), which in many ways is consistent with his belief in the power of common knowledge.
The book makes for compelling but sometimes laborious reading. The many examples require readers to trace recursive patterns of thought carefully instead of simply being able to chunk them. Pinker has to be this fastidious to make his points, but it isn't always easy on the reader. I also wish Pinker put more effort into demonstrating the claim that animates his interest in common knowledge - that it's foundational to human success because it is the basis for social conventions that power our modern world. A lot of this boils down to how language functions, but, surprisingly, Pinker spends little type focusing on spoken and written communication. Additionally, it is unclear how written language fits into the common knowledge model yet written language is almost certainly an important technology that catalyzed human development. It also side-steps the question of how non-human entities may share knowledge. Here, I'm of course thinking about the internet and now genAI chatbots. How can knowledge ever be carefully regulates when it's simply spilling out all over the place. Pinker avoid this dilemma yet the collapse of public-private knowledge and the degradation of common beliefs over the past few decades is arguably an important source of political polarization and dysfunction.
It also strains credulity to believe that recursive mentalization would be particularly important to sustain functional equilibria in various social games. This seems too tenuous. Of course, there is plenty of conflict, but common knowledge itself doesn't preclude conflict (it may provoke it) so it isn't clear that Pinker has really shown that common knowledge is essential. Nonetheless, he has helpfully re-direct my attention to the important of social epistemic.
Ultimately, Pinker's latest book is a really interesting exploration of the dynamics of social knowledge that are largely overlooked in day-to-day life. Plus, it covers a lot of Thomas Schelling's work, which has been incredibly influential but has not always been given its due. If you're a Pinker fan or simply interested in unseen dynamics of social life, then I recommend it.
Extended Review at Substack: Reading the Mind of the Mind Reader
Disclaimer: I received this as an ARC through Netgalley in exchange for an honest review.
Pinker is quite precise about what "common knowledge" is, stating it's a collective epistemic state that results only when A knows X, B knows X, A knows that B knows X, B knows that A knows X, and so on ad infinitum. Pinker boldly claims that this recursive form of social knowledge is the linchpin behind coordination, cooperation, and collective action - otherwise known as the things that make humans human.
Pinker positions his claim as consistent but more foundational than Yuval Noah Harari's in Sapiens, which presents the more widely shared thesis that "our world is built on fictions" specifically the power of belief in various human narratives, including the state, private property, currency, individual rights, etc, is the X-factor that explains human success. The Pinker-cum-Harari thesis, itself narrative, is complemented by more rigorous and scientific theories of human success that are in circulation that still slot fairly neatly into the same paradigm: Acemoglu & Robinson's Why Nations Fail, The Social Brain by Robin Dunbar, and Joseph Henrich's The Secret of Our Successs, and The Theory of Everyone by Michael Muthukrishna. I raise these other works to highlight just how complicated the story of human success is; there isn't a single book or scientific study that's likely to perfectly explain why we've come to the spot we're in today. Pinker himself doesn't invest too much in this narrative in his book yet it is the rationale for why he's assembled a whole book on a seeming mundane idea.
Extending the justification for his interest in common knowledge, Pinker runs through a number of coordination problems that humans face. The examples he provides are typically abstracted, drawing heavily from economics and geopolitics, specifically the sub-field of game theory: the Prisoners' Dilemma, the Stag Hunt, the Battle of the Sexes, Hawks and Doves, etc. These coordination problems inevitably prompt questions about how to resolve them, which allows Pinker to explain the mechanism by which common knowledge can emerge: common salience (a focal point), conspicuity, and recursive mentalizing. Common knowledge doesn't necessarily lead to positive outcome though. Its presence can cause malign coordination as well as beneficial coordination, triggering a number of reciprocal strategies from various parties in a coordination game. Pinker walks through examples of this including bank runs, financial market bubbles, and Keynesian beauty contests.
After exploring the role of common knowledge in abstracted scenarios, Pinker shifts to a focus on social relationships (perhaps the most important human coordination problem), describing the structure of different types of relationships (communal sharing, authority ranking, equality matching, and market pricing - derived from Alan Fiske's work), the mechanisms involved (namely symbolic communication) and the stakes (reputation). This rolls into how our physiology is enmeshed in these dynamics, specifically how conspicuous emotional expressions that generate common knowledge (laughing, crying, blushing, staring, glaring). It also flows into strategies we've deployed to avoid acknowledging common knowledge, such as innuendo and euphemisms, or preclude its development, censorship, cancellation, and strategic hypocrisy. Intriguingly, Pinker invests the entire final chapter defending Plato's concept of the Noble Lie (without using that terminology), which in many ways is consistent with his belief in the power of common knowledge.
The book makes for compelling but sometimes laborious reading. The many examples require readers to trace recursive patterns of thought carefully instead of simply being able to chunk them. Pinker has to be this fastidious to make his points, but it isn't always easy on the reader. I also wish Pinker put more effort into demonstrating the claim that animates his interest in common knowledge - that it's foundational to human success because it is the basis for social conventions that power our modern world. A lot of this boils down to how language functions, but, surprisingly, Pinker spends little type focusing on spoken and written communication. Additionally, it is unclear how written language fits into the common knowledge model yet written language is almost certainly an important technology that catalyzed human development. It also side-steps the question of how non-human entities may share knowledge. Here, I'm of course thinking about the internet and now genAI chatbots. How can knowledge ever be carefully regulates when it's simply spilling out all over the place. Pinker avoid this dilemma yet the collapse of public-private knowledge and the degradation of common beliefs over the past few decades is arguably an important source of political polarization and dysfunction.
It also strains credulity to believe that recursive mentalization would be particularly important to sustain functional equilibria in various social games. This seems too tenuous. Of course, there is plenty of conflict, but common knowledge itself doesn't preclude conflict (it may provoke it) so it isn't clear that Pinker has really shown that common knowledge is essential. Nonetheless, he has helpfully re-direct my attention to the important of social epistemic.
Ultimately, Pinker's latest book is a really interesting exploration of the dynamics of social knowledge that are largely overlooked in day-to-day life. Plus, it covers a lot of Thomas Schelling's work, which has been incredibly influential but has not always been given its due. If you're a Pinker fan or simply interested in unseen dynamics of social life, then I recommend it.
Extended Review at Substack: Reading the Mind of the Mind Reader
Disclaimer: I received this as an ARC through Netgalley in exchange for an honest review.
October 16, 2025
I've really enjoyed the other Pinker books I've read but this book was straight up white noise. Either I got dumber (possible) or there is just no central thesis to this book at all, it's just a series of anecdotes and vague points that add up to nothing. This book is like the over explained version of that episode of Friends where everyone keeps telling Joey "but they don't KNOW that we KNOW they KNOW we KNOW...!" complete with literally explaining that episode of Friends as an example of common knowledge. This one needed more time in the oven.
November 12, 2025
Fascinating, Thoughtful, and Surprisingly Human
As both a mom and a nurse, I’m used to reading people; their moods, their unspoken worries, the things they don’t say out loud. Stephen Pinker’s When Everyone Knows That Everyone Knows put all of that intuition into words. It’s a brilliant and deeply insightful look at how we understand what others are thinking, and how that shared awareness shapes everything from family life to world politics.
Pinker calls it common knowledge. It is what everyone knows and knows that everyone else knows. He explains how this idea quietly drives so much of human behavior: why we coordinate so naturally (like agreeing to drive on the right side of the road), why we sometimes pretend not to notice what’s obvious, and why honesty, though important, can sometimes make life unbearable.
I loved how he connected big global issues like financial bubbles, political movements, even social media shaming, and with small, everyday moments that any parent or caregiver will recognize: the delicate dance of communication, the instinct to protect feelings, the awkwardness of saying goodbye, or pretending not to see the “elephant in the room.”
It’s one of those books that changes how you see the world, and how you see the people right in front of you.
As both a mom and a nurse, I’m used to reading people; their moods, their unspoken worries, the things they don’t say out loud. Stephen Pinker’s When Everyone Knows That Everyone Knows put all of that intuition into words. It’s a brilliant and deeply insightful look at how we understand what others are thinking, and how that shared awareness shapes everything from family life to world politics.
Pinker calls it common knowledge. It is what everyone knows and knows that everyone else knows. He explains how this idea quietly drives so much of human behavior: why we coordinate so naturally (like agreeing to drive on the right side of the road), why we sometimes pretend not to notice what’s obvious, and why honesty, though important, can sometimes make life unbearable.
I loved how he connected big global issues like financial bubbles, political movements, even social media shaming, and with small, everyday moments that any parent or caregiver will recognize: the delicate dance of communication, the instinct to protect feelings, the awkwardness of saying goodbye, or pretending not to see the “elephant in the room.”
It’s one of those books that changes how you see the world, and how you see the people right in front of you.
November 3, 2025
This book low-key ticked me off. It covered the exact same ground as every book over the past 20 years written by someone with the same game-theoretic/mind-is-a-computer perspective. Did it talk about the Prisoners Dilemma? Oh, absolutely, over and over, again and again. What about the Ultimatum game, what about Milgram’s experiments, and Nash equilibrium, and Bayes’s? yes, yes, yes, and yes. The same old stuff recycled into this ludicrous tedium of infinitely recursive recognition hinted at by the equally ludicrous title.
I can see that the author felt this a vital time to publish another book because he believes his approach can heal the political divide, but no one need read it if they’ve read anything in the field since 1990.
The book wasn’t informative nor actionable, but all the cartoons and anecdotes at least made it relatively amusing.
I can see that the author felt this a vital time to publish another book because he believes his approach can heal the political divide, but no one need read it if they’ve read anything in the field since 1990.
The book wasn’t informative nor actionable, but all the cartoons and anecdotes at least made it relatively amusing.
December 21, 2025
Here’s what I learned from the book, “When Everyone Knows That Everyone Knows…” by Steven Pinker:
Common knowledge exists when people not only know something, but also know that others know it. This added layer of awareness changes behavior in powerful ways. Even when information is already known privately, learning it in public can shift outcomes because it creates shared certainty. This explains why public events, statements, and signals matter so much in social life.
Common knowledge enables coordination. People can act together only when they trust that others will act as well. This shared confidence allows cooperation in relationships, organizations, markets, and entire societies. Public norms, rituals, and conventions help resolve these coordination problems by clarifying expectations. At the same time, these exact mechanisms can produce negative effects, such as group panic, fads, mobs, and widespread silence when people fear standing alone.
People often rely on indirect language, euphemisms, and hints. Direct statements create common knowledge, which can lead to commitments, obligations, or conflicts. Indirect speech keeps meaning flexible and allows people to avoid social consequences they are not ready to face. Many personal and political tensions arise from attempts to create, manage, or prevent common knowledge. Language becomes a central tool for maintaining trust, power, and social stability.
But here was my problem with the book. Pinker may be an expert on language and the mind, but rather than focusing on key ideas, the book is mainly made up of stories and examples that can distract from its message. Each teaching was a small kernel followed by pages of puzzles and scenarios. Frankly, sticking to the main themes, the book could have been a pamphlet.
Common knowledge exists when people not only know something, but also know that others know it. This added layer of awareness changes behavior in powerful ways. Even when information is already known privately, learning it in public can shift outcomes because it creates shared certainty. This explains why public events, statements, and signals matter so much in social life.
Common knowledge enables coordination. People can act together only when they trust that others will act as well. This shared confidence allows cooperation in relationships, organizations, markets, and entire societies. Public norms, rituals, and conventions help resolve these coordination problems by clarifying expectations. At the same time, these exact mechanisms can produce negative effects, such as group panic, fads, mobs, and widespread silence when people fear standing alone.
People often rely on indirect language, euphemisms, and hints. Direct statements create common knowledge, which can lead to commitments, obligations, or conflicts. Indirect speech keeps meaning flexible and allows people to avoid social consequences they are not ready to face. Many personal and political tensions arise from attempts to create, manage, or prevent common knowledge. Language becomes a central tool for maintaining trust, power, and social stability.
But here was my problem with the book. Pinker may be an expert on language and the mind, but rather than focusing on key ideas, the book is mainly made up of stories and examples that can distract from its message. Each teaching was a small kernel followed by pages of puzzles and scenarios. Frankly, sticking to the main themes, the book could have been a pamphlet.
November 12, 2025
This would be a great topic for a few chapters, I’m not sure it merited a whole book. A lot of interesting stuff, but some of it was eye-glazing. “He knows that she knows that he knows that she…” and “everyone knows but not everyone realizes that everyone else knows” are important concepts but I think a lot of the examples just go overboard.
I’m giving this book 4 stars because I just like reading Pinker too much to give it 3, but if there were half-stars available I’d probably do 3.5.
I’m giving this book 4 stars because I just like reading Pinker too much to give it 3, but if there were half-stars available I’d probably do 3.5.
October 3, 2025
This is another brilliant Steven Pinker book. It is full of insights, logic, intelligent observations, as well as a little bit of clever humor. Here, Pinker examines common knoladge. The title of the book explains what that term means. The book illuminates just how important that this concept is. Common knowledge is examined from multiple angles. The psychology underlying it, its sociology, its effects on individuals and society, as well as other aspects are explored. The book also includes lots of descriptions of logic games, puzzles as well as personal anecdotes. The author tries to illustrate just how important common knowledge is to humanity.
I have read multiple books by Pinker, and I think that he is one of the world’s greatest intellects. I believe that his books are instrumental in understanding the world and I recommend them all the time. Thus, I went into this expecting a lot. I mostly was not disappointed.
With all that, as several other reviewers have pointed out, this is not most important topic that the author has focused on. In addition, while the book was at times fascinating, it was occasionally a bit dull. As Pinker explained some of the psychological theories involving common knowledge, things became tedious.
I would recamend this book. Though this probably would not be the first Pinker work that I would read. But for those who appreciate the author’s other works, or who are particularly interested in the subjects covered, this is a worthwhile read.
I have read multiple books by Pinker, and I think that he is one of the world’s greatest intellects. I believe that his books are instrumental in understanding the world and I recommend them all the time. Thus, I went into this expecting a lot. I mostly was not disappointed.
With all that, as several other reviewers have pointed out, this is not most important topic that the author has focused on. In addition, while the book was at times fascinating, it was occasionally a bit dull. As Pinker explained some of the psychological theories involving common knowledge, things became tedious.
I would recamend this book. Though this probably would not be the first Pinker work that I would read. But for those who appreciate the author’s other works, or who are particularly interested in the subjects covered, this is a worthwhile read.
November 30, 2025
The core message boils down to “common knowledge,” but the book wraps simple ideas in unnecessary complexity. It’s long, dense, and more elaborate than it needs to be.
The ebook runs 341 pages, with notes and references starting at page 260.
Overall: interesting concept, sluggish execution.
The ebook runs 341 pages, with notes and references starting at page 260.
Overall: interesting concept, sluggish execution.
October 2, 2025
This could be such a hit, if Pinker had taken his conclusions just one step further. He solidly lays out really relevant theories of group dynamics and game theory (now much more elaborate than the early days of morally dubious 1970s psychological experiments) and then almost applies them to the internet and social media. For instance, he can explain recursive mentalising (I know you know I know…ad inf.) and common knowledge (we all know = fame or shame) and has a short chapter at the end musing on the current acceleration to utter transparency, but the reasons why we have to stop short, why privacy is not just a good thing (for those who can afford it) but essential for the properly functioning society, there he just stops. It’s a shame because it really doesn’t take much knowledge of social media to apply the rules (lacking eye contact or sight of the poster, we reach for extra clues in the comments and can easily over-do the laugh, cry, blush, shrug or glare that would temper our verbal utterances). But he doesn’t go there and the book would be much more interesting if he did.
Always with legacy authors who have stuck their necks out (thinking of Richard Dawkins here) Pinker looks at the modern Western world and has a view. Here he tries carefully to paint both sides of the argument and does pretty well, for instance exploring freedom of speech at his institution, Harvard.
One area Pinker really could improve however is his experiment with innuendo. It would be fascinating to see how many of the participants were women, indeed how the results were collated and analysed (by men and/or women?), because the conclusion was that everyone prefers innuendo to bald statements, as a (sexual) refusal can then be shrugged off and the relationship resumed (still friends). The implications for rape cases - I thought she said yes, or at least she didn’t say no - are utterly absent here and women, who stand to benefit from plain speaking, are not reported separately here.
A useful read but not as much fun as it could be.
Always with legacy authors who have stuck their necks out (thinking of Richard Dawkins here) Pinker looks at the modern Western world and has a view. Here he tries carefully to paint both sides of the argument and does pretty well, for instance exploring freedom of speech at his institution, Harvard.
One area Pinker really could improve however is his experiment with innuendo. It would be fascinating to see how many of the participants were women, indeed how the results were collated and analysed (by men and/or women?), because the conclusion was that everyone prefers innuendo to bald statements, as a (sexual) refusal can then be shrugged off and the relationship resumed (still friends). The implications for rape cases - I thought she said yes, or at least she didn’t say no - are utterly absent here and women, who stand to benefit from plain speaking, are not reported separately here.
A useful read but not as much fun as it could be.
December 3, 2025
When Everyone Knows That Everyone Knows offers a sharp, accessible exploration of how common knowledge shapes cooperation, conflict, hypocrisy, and social norms. Steven Pinker blends cognitive science, game theory, and real-world examples to show why societies often rely on strategic ambiguity, polite fictions, and unspoken rules—and why these forms of “rational hypocrisy” can be essential for stability. The book is clear, thoughtful, and intellectually stimulating, especially in its discussion of higher-order reasoning and the human capacity to reflect on our own thinking. A highly engaging read for anyone interested in psychology, rationality, and the hidden structures of social life.
Did Not Finish
January 15, 2026I might come back to this later, but I’m not feeling it right now!
June 29, 2025
Оценка 3.5/5
Това е първата ми среща с книгите на Стивън Пинкър. В нея той разглежда понятието "обща култура" не в традиционния смисъл (знания по различни теми), а като споделено разбиране на дадена ситуация – аз виждам, че ти виждаш нещо, и ти осъзнаваш, че аз съм наясно с това, което ти виждаш, и така нататък. Тази идея е илюстрирана с множество примери от различни аспекти на ежедневието.
Това е първата ми среща с книгите на Стивън Пинкър. В нея той разглежда понятието "обща култура" не в традиционния смисъл (знания по различни теми), а като споделено разбиране на дадена ситуация – аз виждам, че ти виждаш нещо, и ти осъзнаваш, че аз съм наясно с това, което ти виждаш, и така нататък. Тази идея е илюстрирана с множество примери от различни аспекти на ежедневието.
August 2, 2025
Thinking about what other people think
I discovered Steve Pinker’s books a number of years ago via his wonderful description of the psychology of language in The Language Instinct and have enjoyed his discussions of how we think in many aspects of our lives in a number of his other books. When Everyone Knows That Everyone Knows… explores not just what we think but also what we think other people think and the effects of that thinking on our lives. Let me warn you---this book takes some thinking!
The first chapter gives an in-depth discussion of common knowledge, not only do I know it and you know it but I know you know it and vice versa, with the goal of showing how the concept illuminates many enigmas of our public affairs and personal lives. Each succeeding chapter explores common knowledge in some aspect of our lives and society.
The topics treated varied significantly, but they were all thought-provoking. From a pure enjoyment perspective, my favorite was probably Fun and Games, an area where what I think you think and vice versa can be crucial. Laughing, Crying, Blushing, Staring, Glaring looks at our emotional expressions as generators of common knowledge. My favorite chapters were probably the concluding ones, on The Canceling Instinct, the urge to prevent ideas from becoming common knowledge, and Radical Honesty, Rational Hypocrisy, on why not everything should be common knowledge. This would be a good book to read a chapter at a time, to give you a chance to ponder the ideas and also to give your brain a bit of a break!
Not surprisingly, Pinker cites a number of other thinkers, such as Yuval Harari, Robert Aumann, and Charles Darwin, and even quotes Mark Twain.
Lest the playful title mislead you, this book is not a quick read! The ideas are very thought-provoking and caused me to stop and ponder a number of times. On the down side, though, the style was rather academic, and some terms could have been better defined or clearer, but he carefully defined some terms that I would expect any reader of this book to know.
Overall, this is not a book to sit down with for a relaxed and quiet evening, but it is a good choice if you are looking for a book that will make you think, even if it is thinking about what other people think.
I received an advance review copy of this book from Edelweiss and Simon and Schuster.
I discovered Steve Pinker’s books a number of years ago via his wonderful description of the psychology of language in The Language Instinct and have enjoyed his discussions of how we think in many aspects of our lives in a number of his other books. When Everyone Knows That Everyone Knows… explores not just what we think but also what we think other people think and the effects of that thinking on our lives. Let me warn you---this book takes some thinking!
The first chapter gives an in-depth discussion of common knowledge, not only do I know it and you know it but I know you know it and vice versa, with the goal of showing how the concept illuminates many enigmas of our public affairs and personal lives. Each succeeding chapter explores common knowledge in some aspect of our lives and society.
The topics treated varied significantly, but they were all thought-provoking. From a pure enjoyment perspective, my favorite was probably Fun and Games, an area where what I think you think and vice versa can be crucial. Laughing, Crying, Blushing, Staring, Glaring looks at our emotional expressions as generators of common knowledge. My favorite chapters were probably the concluding ones, on The Canceling Instinct, the urge to prevent ideas from becoming common knowledge, and Radical Honesty, Rational Hypocrisy, on why not everything should be common knowledge. This would be a good book to read a chapter at a time, to give you a chance to ponder the ideas and also to give your brain a bit of a break!
Not surprisingly, Pinker cites a number of other thinkers, such as Yuval Harari, Robert Aumann, and Charles Darwin, and even quotes Mark Twain.
Lest the playful title mislead you, this book is not a quick read! The ideas are very thought-provoking and caused me to stop and ponder a number of times. On the down side, though, the style was rather academic, and some terms could have been better defined or clearer, but he carefully defined some terms that I would expect any reader of this book to know.
Overall, this is not a book to sit down with for a relaxed and quiet evening, but it is a good choice if you are looking for a book that will make you think, even if it is thinking about what other people think.
I received an advance review copy of this book from Edelweiss and Simon and Schuster.
February 8, 2026
3.5 stars. There’s a lot here, but in places it feels like he’s reaching, and ultimately it doesn’t quite hang together as a cohesive work. Also the stuff about academic freedom being threatened from the left, though not false, already feels dated in 2026.
January 17, 2026
4.5 stars would be best.
As with other Pinker books, it’s brilliantly written. This was for me a rare non-fiction book that I read out of pure curiosity (less “I’m reading this because it’s about an important time in history I want to understand”). The book has interesting thoughts on how lots of social mores work (dating, jokes, bribes). His final thoughts on how to handle taboo truths were quite wise (don’t bring them up, but don’t make policies that go against those truths).
As with other Pinker books, it’s brilliantly written. This was for me a rare non-fiction book that I read out of pure curiosity (less “I’m reading this because it’s about an important time in history I want to understand”). The book has interesting thoughts on how lots of social mores work (dating, jokes, bribes). His final thoughts on how to handle taboo truths were quite wise (don’t bring them up, but don’t make policies that go against those truths).
May 15, 2026
This is the first book I ever pre-ordered. I knew it would be good before I knew it was good because I knew that I knew it would be good before I knew that it was good because I knew that I knew that I knew...
December 31, 2025
a little mind numbing as you go into infinite regress of I know you know I know… but a brilliantly fresh application of common (or as pinker would like to call - mutual) knowledge
February 4, 2026
Het is eigenlijk heel logisch, maar heb er nooit bij stil gestaan dat gemeenschappelijke kennis zó belangrijk is. Na het zoveelste gedachte-experiment had ik het wel een beetje gehad.
October 11, 2025
Another hit by Steven Pinker. The concept took a bit to wrap my head around but once I did it was evident that it had serious implications. Humans sure are complicated! Sometimes I wonder if I am a bit broken because I don't navigate the nuanced world of layers of pretending, but I suppose we all do to some extent. Worth reading, as is everything by Steven Pinker that I've read.
Did Not Finish
September 25, 2025I won this book in a Goodreads giveaway. I had read a few of Steven Pinker's books back when he was still writing about his area of expertise (language) and thought they were great. I remained aware of him and his assorted forays into wider territory but never actually read anything, but this seemed like it could potentially cover a lot of interesting ground, so I was happy to win the giveaway. Unfortunately, it just doesn't seem sufficient to write a book around. Sure, the concept of common knowledge can touch on a lot of interesting phenomena, but overall it just didn't seem like there was much to the book but a series of things, that didn't feel particularly in depth or edifying and after wading through a few chapters waiting for it to get somewhere, I just gave up on it as not particularly worth my time.
December 6, 2025
Did not finish. Surprised I got halfway through. The recursion became quite tedious and beyond the first chapter did not contribute to the content. I found the writing unclear as well as tedious. It would be harsh to call the book a waste of words, so I’ll stop short of doing so.
December 8, 2025
I just about made it to the 50% mark before abandoning. The reason I made it that far is because the subject of common knowledge is fascinating. The reason I could not go on is because Pinker's writing in this book is absolutely maddening in audiobook form. There are probably at least 3 dozen instances where it'll be some variation of "they know that you know that they know that you know that they know..."and it's (apparently) important to bring out the multiple dimensions of infinite in a way that just "they know that you know that they know" wouldn't suffice. Also, Pinker is one of those academic writers who seems to struggle to come down to a popular level, at least for me. If this was in print form and taken at a leisurely pace, it might go better. In the meantime, I'd be happy to just read a summary with a few examples rather than continue to labor through this.
October 5, 2025
Huge Pinker fan and Better Angels should be required reading for all the “sky is falling” crowd that is panicking about the state of the word in every generation (not that it will make a difference, but maybe for 1 in 500 it will). This book, however, is impenetrable or at least beyond me, felt unnecessarily long, with few to zero practical tips beyond noting that we are generally poor rational thinkers.
June 17, 2026
"As a cognitive scientist, I have spent my life thinking about how people think. So the ultimate subject of my fascination would have to be how people think about what other people think, and how they think about what other people think they think, and how they think about what other people think they think they think..."
I was excited to start When Everyone Knows That Everyone Knows, but unfortunately, it did not live up to the high-water mark the author established for me in his other books. The book is my fifth from the author, and probably my least favorite of the five. Ultimately, the writing was just too long and boring for my finicky tastes. Although common knowledge is an interesting topic, I feel like the writing here was too lengthy and bloated. The entire book could have been edited down by 50-60% with no loss to the overall presentation. However, bonus points could be added here for his shot across the bow at cancel culture and the woke PC mob in the latter chapters.
Author Steven Arthur Pinker is a Canadian cognitive psychologist, psycholinguist, popular science author, and public intellectual. He is an advocate of evolutionary psychology and the computational theory of mind.
Steven Pinker:
The intro of the book was a bit lacklustre compared to his other works. He drops the quote above near the start, and expands on the definition of "common knowledge":
In this short blurb Pinker outlines the aim of the book:
Some more of what the author covers here includes:
• Game Theory: Shifting past simple individual logic to look at the strategic, recursive loops of group coordination.
• Bank Runs & Market Crashes: How a sudden shift in collective trust instantly collapses arbitrary economic realities.
• The Bystander Effect: The structural paralysis that occurs when everyone knows an issue exists, but waits for an external signal to act.
• Social Norms & Forbidden Knowledge: Why communities use strategic ambiguity and doublespeak to intentionally prevent common knowledge from forming.
• Cancel Culture & Shaming Mobs: The modern weaponization of public awareness to force immediate group alignment and punish dissent.
********************
Unfortunately, as touched on at the start of this review, I found much of the writing here dry. The prose lacked the typical panache of Pinker's writing. The journey through was not as lively as other books of his that I really enjoyed, like Enlightenment Now and The Better Angels of Our Nature.
3 stars.
I was excited to start When Everyone Knows That Everyone Knows, but unfortunately, it did not live up to the high-water mark the author established for me in his other books. The book is my fifth from the author, and probably my least favorite of the five. Ultimately, the writing was just too long and boring for my finicky tastes. Although common knowledge is an interesting topic, I feel like the writing here was too lengthy and bloated. The entire book could have been edited down by 50-60% with no loss to the overall presentation. However, bonus points could be added here for his shot across the bow at cancel culture and the woke PC mob in the latter chapters.
Author Steven Arthur Pinker is a Canadian cognitive psychologist, psycholinguist, popular science author, and public intellectual. He is an advocate of evolutionary psychology and the computational theory of mind.
Steven Pinker:
The intro of the book was a bit lacklustre compared to his other works. He drops the quote above near the start, and expands on the definition of "common knowledge":
"...As dizzying as this cogitation may seem, we engage in it every day, at least tacitly, and in the limit this state of awareness has a technical name, common knowledge..."
"...Originating in game theory and philosophy, the theory of common knowledge can illuminate a vast range of puzzles about human social life. I first came across it through my interest in language when writing The Stuff of Thought. I had long wondered why people often don’t say what they mean in so many words but veil their intentions in innuendo and doublespeak, counting on their listeners to read between the lines. The answer, I suggested, was that barefaced statements generate common knowledge but genteel euphemisms do not, and common knowledge is what ratifies or annuls social relationships."
In this short blurb Pinker outlines the aim of the book:
"In this book I’ll expand on that theory and show how common knowledge also explains fundamental features of societal organization, such as political power and financial markets; some of the design specs of human nature, such as laughter and tears; and countless curiosities of private and public life, such as bubbles and crashes, road rage, anonymous donations, long goodbyes, revolutions that come out of nowhere, social media shaming mobs, and academic cancel culture. By the time you finish the book I hope you’ll be equipped to understand phenomena I never got around to explaining, such as gaslighting, Kardashian celebrity (being famous for being famous), mock outrage (“I’m shocked, shocked to find that gambling is going on in here”), “red lines” in international relations, and the psychological difference between “cc” and “bcc” in email etiquette."
Some more of what the author covers here includes:
• Game Theory: Shifting past simple individual logic to look at the strategic, recursive loops of group coordination.
• Bank Runs & Market Crashes: How a sudden shift in collective trust instantly collapses arbitrary economic realities.
• The Bystander Effect: The structural paralysis that occurs when everyone knows an issue exists, but waits for an external signal to act.
• Social Norms & Forbidden Knowledge: Why communities use strategic ambiguity and doublespeak to intentionally prevent common knowledge from forming.
• Cancel Culture & Shaming Mobs: The modern weaponization of public awareness to force immediate group alignment and punish dissent.
********************
Unfortunately, as touched on at the start of this review, I found much of the writing here dry. The prose lacked the typical panache of Pinker's writing. The journey through was not as lively as other books of his that I really enjoyed, like Enlightenment Now and The Better Angels of Our Nature.
3 stars.
January 4, 2026
What does canceledpeople.org have to do with the subject of Common Knowledge? Pinker argues for a sharpening of Yuval Harari’s thesis that human society depends on stories, on fictions. Fictions as apparently unassailable as corporations, money, and national borders. What I think Pinker argues is that it’s not the fiction per se that makes it important, it is the fact of it being common knowledge.
Common knowledge exists when everyone knows, and everyone sees everyone else knowing at the same time. In the story of the Emperor Has No Clothes, at the moment just before the little boy calls out, everyone knew that the Emperor was naked. But, everyone in the crowd could still believe that perhaps other people were seeing it differently. Once the boy says “he has no clothes,” and everyone heard him say it, and at the same time saw everyone else hear him say it, then the Emperor’s nakedness became common knowledge.
Returning to Harari’s Ur examples of currency and the rest, those things are essential for allowing us, humans, to coordinate our actions. Life would be untenable if we didn’t all agree that those things exist. And the list of common knowledge goes on and on: everything from the meanings of words, to the side of the road you drive on and what one does at red lights.
That the list of what’s common knowledge is so open-ended raises the question of how things enter the sphere of common knowledge in the first place. And here, we collide with the newish phenomenon of social media, which (crucially) carry the possibility for any individual to create common knowledge.
When someone puts out a Tweet saying that (for instance; this isn’t a dog whistle) “systemic racism doesn’t exist,” it’s analogous to the little boy in the story saying it. Although we haven’t built the rules of our society on the belief in systemic racism, nonetheless enough people believe in it that a public denial of it is threatening. To forestall the feared outcome of the heretical idea becoming common knowledge, it is necessary to publicly punish the little boy. The populace surrounds him and beats him to death. The Emperor is unperturbed in his nakedness.
Pinker mentions the website canceledpeople.org, and if you go there, you can find hundreds of examples. Liz Cheny is one of them: just to emphasize that this cancellation culture works in both directions from the Great Political Divide. The common factor is always the existence of an “informal coalition”, as quoted below (p31).
My enthusiasm for Pinker’s work product reached a local maximum on p.59, where he cogently articulates why “courtesy is a poor basis for coordination [of pedestrian traffic crossings]: we’re both better off hewing to convention and taking advantage of the common-knowledge generators that were created for just that purpose, namely traffic lights and zebra crossings.” YES. I want no more would-be traffic heroes waving me across four lanes of traffic against a light.
JUST GO. DAMN IT.
I buy into Pinker’s synthesis and do think the idea that recursive thinking-about-thinking-about-thinking, and how it is baked into the functioning of society, is one of those Big Ideas with great explanatory power. It would be too tedious to reflect on all the examples of the book, but I want to throw in some language examples to illustrate how fundamental the idea is; here are some verbs and their deconstructed recursive mentalisms:
- Bluff: Amy wants Brad to believe that Amy believes something which Amy doesn’t believe.
- Conceal from: Amy wants Brad not to know something Amy knows.
- Doubt: Amy wants Brad to believe something Amy doesn’t believe.
Common knowledge exists when everyone knows, and everyone sees everyone else knowing at the same time. In the story of the Emperor Has No Clothes, at the moment just before the little boy calls out, everyone knew that the Emperor was naked. But, everyone in the crowd could still believe that perhaps other people were seeing it differently. Once the boy says “he has no clothes,” and everyone heard him say it, and at the same time saw everyone else hear him say it, then the Emperor’s nakedness became common knowledge.
Returning to Harari’s Ur examples of currency and the rest, those things are essential for allowing us, humans, to coordinate our actions. Life would be untenable if we didn’t all agree that those things exist. And the list of common knowledge goes on and on: everything from the meanings of words, to the side of the road you drive on and what one does at red lights.
That the list of what’s common knowledge is so open-ended raises the question of how things enter the sphere of common knowledge in the first place. And here, we collide with the newish phenomenon of social media, which (crucially) carry the possibility for any individual to create common knowledge.
When someone puts out a Tweet saying that (for instance; this isn’t a dog whistle) “systemic racism doesn’t exist,” it’s analogous to the little boy in the story saying it. Although we haven’t built the rules of our society on the belief in systemic racism, nonetheless enough people believe in it that a public denial of it is threatening. To forestall the feared outcome of the heretical idea becoming common knowledge, it is necessary to publicly punish the little boy. The populace surrounds him and beats him to death. The Emperor is unperturbed in his nakedness.
Pinker mentions the website canceledpeople.org, and if you go there, you can find hundreds of examples. Liz Cheny is one of them: just to emphasize that this cancellation culture works in both directions from the Great Political Divide. The common factor is always the existence of an “informal coalition”, as quoted below (p31).
“Norms exist only insofar as everyone knows they exist and knows that everyone else knows it. This makes them vulnerable to unraveling if they are publicly flouted, and that can have harmful consequences. To take a simple example, if someone believes it’s OK to drive through red lights, they are a danger to others, and an even worse danger if still other drivers inferred it was OK. To take a more complicated one, faith-based communities and other informal coalitions may punish heretics and infidels who cast doubt on the common dogmas that bind them in a pact of coordination. And to take a contemporary example, Saaco (and many other cancelees), by treating racism with less than the appropriate awe and dread, were undermining the belief that racism is insidious, unconscious, and ubiquitous, and thus were seen as threats to the relentless vigilance necessary to extirpate it.
…Like Haidt, I think this explains why the last decade of American life has been uniquely stupid.
My enthusiasm for Pinker’s work product reached a local maximum on p.59, where he cogently articulates why “courtesy is a poor basis for coordination [of pedestrian traffic crossings]: we’re both better off hewing to convention and taking advantage of the common-knowledge generators that were created for just that purpose, namely traffic lights and zebra crossings.” YES. I want no more would-be traffic heroes waving me across four lanes of traffic against a light.
JUST GO. DAMN IT.
I buy into Pinker’s synthesis and do think the idea that recursive thinking-about-thinking-about-thinking, and how it is baked into the functioning of society, is one of those Big Ideas with great explanatory power. It would be too tedious to reflect on all the examples of the book, but I want to throw in some language examples to illustrate how fundamental the idea is; here are some verbs and their deconstructed recursive mentalisms:
- Bluff: Amy wants Brad to believe that Amy believes something which Amy doesn’t believe.
- Conceal from: Amy wants Brad not to know something Amy knows.
- Doubt: Amy wants Brad to believe something Amy doesn’t believe.
October 21, 2025
An above-average edition of Reader's Digest.
Notes
Our world is built on conventions that allow us to coordinate effectively and are self-reinforcing because of common knowledge.
Goods consumed in public more likely to be advertised during Superbowl than consumed in private. Depends on everyone knowing that everyone knows.
Communities have an incentive to enforce norms by publicly punishing flouters so the common knowledge assures that the norms still hold.
Convention is more efficient than courtesy when it comes to coordination, so we create common knowledge generators like zebra-crossings and traffic lights.
Rousseau’s Stag Hunt: every hunter is tempted by selfishness/impatience to pursue the small but sure reward of a hare over a larger less certain reward of the stag for which his fellow hunters depend on his cooperation. Bank runs are Stag Hunts, everyone must have confidence that everyone else has confidence and noone seeks to withdraw (federal deposit insurance).
Piaget’s Concrete Operations stage of cognitive development, or Age of Reason, when children understand 2nd order mentalizing (I know that John thinks that Mary thinks X). Adults test drops off a cliff at 5th order, so maybe we have 4 slots - better for people with better working memory, language skill, and lower autism.
Laughter generates common knowledge of an indignity that undermines a claim to dominance/status to be used aggressively (challenge a dominant figure) or convivially (signal that dominant-subordinate does not apply).
Darwin’s ‘antithesis’ - animal in a state opposite to one that triggers a certain posture, produces the physically opposite posture: dog in attack-mode is stiff body, rigid tail, teeth bared vs friendly mode - wagging tail, wriggling body, slack ears/lips. Human laughter (long inhale, short ha ha exhales, muscles contract) vs crying (short deep gasp inhales, long sigh exhale, body slumps)
Two of three negative self-conscious emotions (embarrassment, shame) trigger blushing, but not the third (guilt). Blush when accused even when innocent, that others think I’m guilty causes it. Embarrassment is public breach of social norm vs Shame is public breach of moral norm. Blushing functions as nonverbal apology.
Eye contact is the ultimate common knowledge generator - we are seeing the part of the person that sees us see them see us.
Notes
Our world is built on conventions that allow us to coordinate effectively and are self-reinforcing because of common knowledge.
Goods consumed in public more likely to be advertised during Superbowl than consumed in private. Depends on everyone knowing that everyone knows.
Communities have an incentive to enforce norms by publicly punishing flouters so the common knowledge assures that the norms still hold.
Convention is more efficient than courtesy when it comes to coordination, so we create common knowledge generators like zebra-crossings and traffic lights.
Rousseau’s Stag Hunt: every hunter is tempted by selfishness/impatience to pursue the small but sure reward of a hare over a larger less certain reward of the stag for which his fellow hunters depend on his cooperation. Bank runs are Stag Hunts, everyone must have confidence that everyone else has confidence and noone seeks to withdraw (federal deposit insurance).
Piaget’s Concrete Operations stage of cognitive development, or Age of Reason, when children understand 2nd order mentalizing (I know that John thinks that Mary thinks X). Adults test drops off a cliff at 5th order, so maybe we have 4 slots - better for people with better working memory, language skill, and lower autism.
Laughter generates common knowledge of an indignity that undermines a claim to dominance/status to be used aggressively (challenge a dominant figure) or convivially (signal that dominant-subordinate does not apply).
Darwin’s ‘antithesis’ - animal in a state opposite to one that triggers a certain posture, produces the physically opposite posture: dog in attack-mode is stiff body, rigid tail, teeth bared vs friendly mode - wagging tail, wriggling body, slack ears/lips. Human laughter (long inhale, short ha ha exhales, muscles contract) vs crying (short deep gasp inhales, long sigh exhale, body slumps)
Two of three negative self-conscious emotions (embarrassment, shame) trigger blushing, but not the third (guilt). Blush when accused even when innocent, that others think I’m guilty causes it. Embarrassment is public breach of social norm vs Shame is public breach of moral norm. Blushing functions as nonverbal apology.
Eye contact is the ultimate common knowledge generator - we are seeing the part of the person that sees us see them see us.
October 7, 2025
I’ll be honest: I would’ve enjoyed this book far more had I started with Chapter 8. If it were going on my shelf, I’d probably staple the first seven chapters together—not because they’re terrible, but because they’re painfully repetitive, redundant. Pinker spends hundreds of pages proving, via endless game-theory experiments, that “common knowledge” is the social glue that makes coordination, trust, and cooperation possible.
We get it. Everyone knows what everyone knows. And by Chapter 6, everyone knows they know that.
But then came Chapter 8, where the abstract finally collides with the real world—specifically, the messy cultural experiment of cancel culture. Here, Pinker stops diagramming thought bubbles and starts dissecting a social pathology. He explains that when knowledge of a moral rule becomes publicly shared and publicly monitored, people enforce it performatively. Not because they believe it, but because they know everyone else knows they’re supposed to and lying to ourselves feels better than being on the outside of the hive.
Cancel culture is more than deplatforming outrage—it’s a self-reinforcing system of conforming stupidity. Once an accusation becomes common knowledge, in spite of how ridiculous it is, the social cost of dissent skyrockets and we all turn into lemmings. People virtue signal to avoid being the next target, and the cycle feeds itself and the cancer grows. “Maoist incentive structure” of modern life: moral purity achieved through public denunciation.
Common knowledge is gasoline for social punishment. Everyone joins the mob, even if no one actually believes the slogans. In hindsight all we could ever be is a digital Red Guard—feeling righteous and vindicated through synchronized hate. And Pinker, to his credit, doesn’t just wag his finger from a distance. He sounds genuinely embarrassed to belong to the academic establishment that fuels this hysteria.
By the end of the chapter, you can feel his exasperation: a lifelong rationalist watching reason devour itself. When everyone knows what everyone knows but what everyone knows is hollow, courage evaporates, truth bends, and wisdom slips quietly out the back door.
The rest of the book is ok but Chapter 8? That’s Pinker with his sleeves rolled up, finally admitting that ivory towers of coercion through common knowledge at the expense of sanity is dumb. Dumb dumb dumb.
Loved it.
February 18, 2026
This was a bit like a tongue twister for my brain. It explores “recursive mentalizing” as in “he knows that she knows that he knows that she knows”, which taken ad infinitum sums to “common knowledge”.
The big takeaway was that humans treat something that is truly common knowledge (everyone knows that everyone knows) differently from private knowledge or even reciprocal knowledge, and the math supports that as rational.
Some really cool stuff in here. There was the usual game theory discussions of prisoners dilemma, but also of “stag hunt”, “battle of the sexes”, “chicken”, etc. In these games, common knowledge can be used to solve the coordination problems to get to win-win scenarios.
Conversely, there are many times humans desperately want to avoid common knowledge, and a lot of otherwise irrational-seeming social niceties make sense in this context.
If you fart in public but you’re sure no one heard you, are you embarrassed? What if someone did hear you but you don’t think they know you know that? If you can keep up the pretense that you don’t know they know you know … ad infinitum, you probably aren’t embarrassed, but if it becomes ratified as “common knowledge” (e.g. by eye contact or a sudden loud silence) then you are.
Also:
- why it is rational to use innuendo (ie avoiding direct speech to avoid common knowledge) for veiled bribes, threats, or sexual advances
- the dangers of cancel culture and the self-muzzling of research institutions
- biological traits that ensure common knowledge (eg direct speech, eye contact, blushing, laughing, crying)
It was a bit of a slog to get through, though I think that was mostly due to the constant brain-bending recursion problems, which Pinker did his best to keep as straightforward as possible.
The big takeaway was that humans treat something that is truly common knowledge (everyone knows that everyone knows) differently from private knowledge or even reciprocal knowledge, and the math supports that as rational.
Some really cool stuff in here. There was the usual game theory discussions of prisoners dilemma, but also of “stag hunt”, “battle of the sexes”, “chicken”, etc. In these games, common knowledge can be used to solve the coordination problems to get to win-win scenarios.
Conversely, there are many times humans desperately want to avoid common knowledge, and a lot of otherwise irrational-seeming social niceties make sense in this context.
If you fart in public but you’re sure no one heard you, are you embarrassed? What if someone did hear you but you don’t think they know you know that? If you can keep up the pretense that you don’t know they know you know … ad infinitum, you probably aren’t embarrassed, but if it becomes ratified as “common knowledge” (e.g. by eye contact or a sudden loud silence) then you are.
Also:
- why it is rational to use innuendo (ie avoiding direct speech to avoid common knowledge) for veiled bribes, threats, or sexual advances
- the dangers of cancel culture and the self-muzzling of research institutions
- biological traits that ensure common knowledge (eg direct speech, eye contact, blushing, laughing, crying)
It was a bit of a slog to get through, though I think that was mostly due to the constant brain-bending recursion problems, which Pinker did his best to keep as straightforward as possible.
December 31, 2025
Wow. What a book. If you are a fan of Steven Pinker, then this book "When Everyone Knows that Everyone knows" will not disappoint. I had previously read his book "The Better Angels of Our Nature" and was very impressed by his research and the thoroughness with which he writes. This book follows in his pattern of excellent books.
Pinker's latest book explores the idea of "common knowledge", what it is, what makes it common, and how it is used and applied on everyday life. This might sound like a dull subject, but it certainly is not. Pinker applies his trademark brand of logic and dives deeply into the subject, even employing the tenants of game theory to support his assertions. It turns out that common knowledge is intrinsically tied up with the idea of humanity and the cultures that we have built.
Pinker's discussion of the applications of common knowledge left me with many aha moments, and just as many scratching my head moments. I was especially intrigued by the chapter on why people cannot just say what they mean and so much of human conversation is covered up by double-speak, reading between the lines, innuendo, and the like. It is a fascinating subject and Pinker does a great exploring common knowledge. I will definitely have to read this again, after I have had time to think about it more deeply.
Pinker's latest book explores the idea of "common knowledge", what it is, what makes it common, and how it is used and applied on everyday life. This might sound like a dull subject, but it certainly is not. Pinker applies his trademark brand of logic and dives deeply into the subject, even employing the tenants of game theory to support his assertions. It turns out that common knowledge is intrinsically tied up with the idea of humanity and the cultures that we have built.
Pinker's discussion of the applications of common knowledge left me with many aha moments, and just as many scratching my head moments. I was especially intrigued by the chapter on why people cannot just say what they mean and so much of human conversation is covered up by double-speak, reading between the lines, innuendo, and the like. It is a fascinating subject and Pinker does a great exploring common knowledge. I will definitely have to read this again, after I have had time to think about it more deeply.
January 26, 2026
Books introduces some interesting concepts and goes into detail with a few familiar ones (prisoners dilemma, hawk dove game). The first part is a bit to much math for a fluent read. Luckily this part does not last long. It is mandatory to understand the rest of the book.
Understanding multiple levels of they know they know etc can be a bit mind boggeling. The author does a good job at helping the reader to understand the concept. This was done a bit too late in the book in my opinion. Starting with a chapter like that could help to improve the understanding of the book.
Overal a fine read but nothing to write home about, it does take some time to get used to the concepts and wrap your mind around them.
Understanding multiple levels of they know they know etc can be a bit mind boggeling. The author does a good job at helping the reader to understand the concept. This was done a bit too late in the book in my opinion. Starting with a chapter like that could help to improve the understanding of the book.
Overal a fine read but nothing to write home about, it does take some time to get used to the concepts and wrap your mind around them.
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