When Everyone Knows That Everyone Knows . . .: Common Knowledge and the Mysteries of Money, Power, and Everyday Life

by Steven Pinker

Overview

From one of the world’s most celebrated intellectuals, a brilliantly insightful work that explains how we think about each other’s thoughts 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 is necessary for coordination, for making arbitrary but complementary choices like driving on the right, using paper currency, and coalescing behind a political leader or movement. It’s also necessary for social coordination: everything from rendezvousing at a time and place to speaking the same language to forming enduring relationships of friendship, romance, or authority. Humans have a sixth sense for common knowledge, and we create it with signals like laughter, tears, blushing, eye contact, and blunt speech.

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.

Pinker shows how the hidden logic of common knowledge can make sense of many of life’s enigmas: financial bubbles and crashes, revolutions that come out of nowhere, the posturing and pretense of diplomacy, the eruption of social media shaming mobs and academic cancel culture, the awkwardness of a first date. Artists and humorists have long mined the intrigues of common knowledge, and Pinker liberally uses their novels, jokes, cartoons, films, and sitcom dialogues to illuminate social life’s tragedies and comedies. Along the way he answers questions like:

• Why do people hoard toilet paper at the first sign of an emergency?
• Why are Super Bowl ads filled with ads for crypto?
• Why, in American presidential primary voting, do citizens typically select the candidate they believe is preferred by others rather than their favorite?
• Why did Russian authorities arrest a protester who carried a blank sign?
• Why is it so hard for nervous lovers to say goodbye at the end of a phone call?
• Why does everyone agree that if we were completely honest all the time, life would be unbearable?

Consistently riveting in explaining the paradoxes of human behavior, 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.

Product Details

ISBN-13:	9781668011607
Publisher:	Scribner
Publication date:	09/23/2025
Sold by:	SIMON & SCHUSTER
Format:	eBook
Pages:	384

About the Author

Steven Pinker is the Johnstone Professor of Psychology at Harvard University.  He has won many prizes for his teaching, his research on language, cognition, and social relations, and his twelve books, including The Language Instinct, How the Mind Works, The Better Angels of Our Nature, and Rationality. He is an elected member of the National Academy of Sciences, a two-time Pulitzer Prize finalist, and one of Time’s “100 Most Influential People in the World Today.”

Hometown:

Boston, Massachusetts

Date of Birth:

September 18, 1954

Place of Birth:

Montreal, Canada

Education:

B.A., McGill University, 1976; Ph.D., Harvard University, 1979

Website:

http://stevenpinker.com/

Editorial Reviews

“When Everyone Knows That Everyone Knows...is one of the most insightful books I’ve read about what makes us human and how we understand each other. It changed how I think about the interactions I have, and I bet it will do the same for you.”
—Bill Gates

“Reading Steven Pinker is always a delight. Each book gives you deep insight into things previously unseen, which then bathes the world we thought we knew in a new light. In When Everyone Knows, Pinker shows us that the transition from various forms of private knowledge to common knowledge is the key cognitive tool for understanding when and how people coordinate to bring about sudden massive change—for better and for worse. If Pinker's ideas become common knowledge, we'll be far better equipped to handle the massive disruptions already arriving in our hyper-networked world.”
—Jonathan Haidt, #1 New York Times bestselling author of The Anxious Generation and coauthor of The Coddling of the American Mind

“Think you know what others think about what you are thinking? It turns out you’re probably wrong. And thanks to When Everyone Knows, now we know why. Once you read this book, you’ll never view human behavior quite the same way again.”
—Jonah Berger, New York Times bestselling author of Contagious and The Catalyst

“An expository masterpiece. Steven Pinker explains, with beautiful clarity, how common knowledge is critical to successful human interaction.”
—Eric Maskin, Nobel Laureate in Economics and Professor at Harvard University

“A masterful look behind the curtain at the calculations that propel us forward. With his brilliant knack for exposing what we take for granted, celebrated cognitive psychologist Steven Pinker explores, among many phenomena, our very human tendency to reveal information strategically, only letting others see what we want them to see. It is a game we all play, wagering bets on how much of what a person is saying tallies with what they’re thinking. Sometimes our bets help us capture what we seek; at other times, we’re proven disastrously wrong. In holding up a mirror to our mental workings, Pinker teaches us how to better turn the odds in our favor.”
—Annie Duke, bestselling author of Thinking in Bets and How to Decide

“A lively exposition of one of the most important and basic concepts in game theory, and the surprising ways it plays out in human affairs.”
—Robert Aumann, Nobel Laureate in Economics and Professor Emeritus at the Hebrew University of Jerusalem

“Insight packed. With brisk authority, Pinker shows that a key aspect of being human, sociality, depends on a mutual understanding of intentions, which allows us to make sense of responses like laughing and blushing and phenomena as various as myth-making and online cancel culture.”
—Daron Acemoglu, Nobel Laureate in Economics and New York Times bestselling author of Why Nations Fail

“With his characteristic wit and clarity, Steven Pinker has written a brilliant exploration of common knowledge as the glue that holds society together—and how its lack can tear the social fabric apart...Essential reading for anyone who wants to understand the rules of the world in which we live—and how to extract maximum value from them to make it a world worth living in.”
—Maria Konnikova, New York Times bestselling author of The Biggest Bluff

From the Publisher

One of the most insightful books I’ve read about what makes us human and how we understand each other. It changed how I think about the interactions I have, and I bet it will do the same for you.”

Bill Gates

2025-05-30
Pinker continues his explorations of the hidden social functions of language and thought with this look at common knowledge.

Common knowledge, as cognitive science Pinker lays it out here, lends itself to the game theory beloved of economists and strategists: Do I know something that you don’t? Can we agree, in order to produce best outcomes, thatX meansX andY meansY? Pinker explains at the outset that “withprivate knowledge, person A knows something, and person B knows it. Withcommon knowledge, A knows something, and B knows it, but in addition, Aknows that B knows it, and B knows that A knows it”—a shared set of data, facts, and assumptions that enable not only cooperation but also coordination. That coordination, Pinker holds, is essential to the functioning of society: Our shared visions allow us to build economies, polities, communities, for which reason he adds that a better term for “common knowledge” would be “mutual knowledge,” which more easily accommodates agreeing on “nonphysical realities.” Pinker offers a vivid example when he notes that people don’t rise up against dictators easily because of the unspoken assumption that everyone else supports the regime, but things can get rolling when a public demonstration yields “the common knowledge needed to coordinate resistance.” Timely, that. Common knowledge has its negative aspects, he adds, as when people come to consensus about some point or another by way of shared media and then move together to punish transgressors. The swiftest way to be misunderstood, he notes, is to use irony or indirect speech, much as they help disguise our intentions. Pinker writes fluently, though there’s plenty of arcana from neuroscience, linguistics, and other fields floating around here. While it’s not necessary to have read Noam Chomsky, Antonio Damasio, Daniel Kahneman, and other cognitive scientists to follow Pinker’s arguments, it helps.

A revelatory, if sometimes challenging, look at the traps and rewards that lie within our words.

Kirkus Reviews