"When Everyone Knows That Everyone Knows" is Steven Pinker's worst book, but it's still fascinating, especially if you're into logic and puzzles.

Disclosure: I've read all of Pinker's books, and I gave them all five stars. I graduated from Harvard, where Pinker teaches. I received a free advanced copy of Everyone Knows That Everyone Knows from the publisher. None of these factors biases my judgment: I give this book 3.5 stars.

When Everyone Knows That Everyone Knows is about common knowledge.

What is common knowledge?

Other terms for common knowledge include open knowledge, conspicuous knowledge, public knowledge, interactive knowledge, shared reality, shared awareness, collective consciousness, and common ground.

Why is common knowledge important?

Many of our tensions, personal and political, arise from the desire to propagate or suppress common knowledge.

What answers does Pinker's book answer?

Pinker's book 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?
Where Pinker disagrees with Yuval Harari

Yuval Harari and Stephen Pinker are among my top 3 authors (I also love Bill Bryson). Therefore, my ears paid attention when Pinker disagreed with a minor point Harari made about humans creating fictions. I quoted one of those fictions when I explained Why is Bitcoin Worth Anything?

Pinker says Harari is too extreme when he categorizes many human inventions as "fictions." Pinker partially agrees, but points out a nuance: 

Our world is built on conventions that allow us to coordinate effectively and are self-reinforcing because they are common knowledge. Conventions like the English language, Christianity, the United States of America, the euro, and Microsoft are not exactly “fictions.” They are very real, even if they are not made out of physical stuff. Common knowledge creates nonphysical realities.

If you have 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, then this is your book.

Funny story

As usual, Pinker litters his book with humor, including comic strips. One of my favorite parts is when he tells this joke:

A defendant was on trial for murder. There was strong evidence indicating his guilt, but there was no corpse. In his closing statement, the defense attorney resorted to a trick.

“Ladies and gentlemen of the jury,” he said. “I have a surprise for you all—within one minute, the person presumed dead will walk into this courtroom.”

He looked toward the courtroom door. The jurors, stunned, all looked eagerly.

A minute passed.

Nothing happened.

Finally the lawyer said, “Actually, I made up the business about the dead man walking in. But you all looked at the door with anticipation. I therefore put it to you that there is reasonable doubt in this case as to whether anyone was killed, and I must insist that you return a verdict of ‘not guilty.’”

The jury retired to deliberate.

A few minutes later, they returned and pronounced a verdict of “guilty.”

“But how could you do that?” bellowed the lawyer. “You must have had some doubt. I saw all of you stare at the door.”

The jury foreman replied, “Oh, we looked, but your client didn’t.”

Social paradox

I learned about a social paradox, a term suggested by the psychologist David Pinsof for phenomena like these:

1. We try to gain status by not caring about status.

2. We rebel against conformity in the same way as everyone else.

3. We show humility to prove we’re better than other people.

4. We don’t care what people think, and we want them to think this.

5. We make anonymous donations to get credit for not caring about getting credit.

6. We bravely defy social norms so that people will praise us.

7. We avoid being manipulative to get people to do what we want them to do.

8. We compete to be less competitive than our rivals.

9. We help those in need, regardless of self-interest, because being seen as the type of person who helps those in need, regardless of self-interest, is in our self-interest.

10. We make subversive art that only high-status people appreciate.

11. We make fun of ourselves for being uncool to prove we’re cool.

12. We self-righteously defend false beliefs to prove we care more about the truth than virtue-signaling.

13. We help our friends without expecting anything in return, because we know they would do the same for us.

14. We show everyone our true, authentic self—not who society wants us to be—because that is who society wants us to be.

Chapter against wokeism

One of the things I admire most about Pinker is that he's a moderate, unlike most of the leftists at Harvard. Pinker spends a chapter destroying the woke ideology and the cancel culture, which is contrary to the open discourse that universities must have.

Conclusion

With so many good passages, why only 3.5 stars? It's because the first 100 pages are filled with tedious logic exercises that disinterested me. In all the other Pinker books, I savor every word. In When Everyone Knows That Everyone Knows, I skipped pages, exhausted by Pinker's nonstop discussion about how John knows what Sally thinks about John knowing about Sally's kid (and far more layered than that!). My eyes rolled.

Still, When Everyone Knows That Everyone Knows is another worthwhile book, even if it's Pinker's worst. Pinker's worst is among the top 1% of all nonfiction books of 2025.

This was a thought-provoking read. Steven Pinker looks at the idea of “common knowledge”—what happens when everyone knows that everyone else knows something—and how it shapes everything from social movements to stock market panics. With clear examples (like the run on toilet paper during COVID), Pinker explains how shared understanding helps people coordinate their behavior in surprising ways. Drawing on psychology and economics, he breaks down big ideas in an accessible way that’s great for readers interested in how group behavior works, even when it seems irrational.

A fine book. Pinker's books are always a hit or miss for me. I liked aspects of it and didn't like other aspects.

Wow. It’s like who’s on first, what’s on second…. The mind trip of trying to read this took some getting over but Steven Pinker is at his best. Best to take it in small bites, but his thinking is amazing as always.

The style of the book is similar to another of Pinker’s books (I’ve read The Stuff of Thought) in the sense that he covers intriguing topics that can be dense but sneaks in humor and plenty of anecdotes to keep it readable. I did find this one to be mildly repetitive, but it didn’t take much away from the overall enjoyment. With how much I enjoyed his other book and with this one also being a great read, I find myself wanting to read through all of Pinker’s works. I could see this potentially boring some people who aren’t particularly interested in human relationships or psych, but I found it quite enjoyable. This would be a 4.5/5 star read for me, but I’ll round up for the lack of half star rating ability. I will definitely want to add this book to my physical library!

Steven Pinker does it again! He’s such a masterful storyteller, weaving illustrations and facts to relay powerful messages to the audience. I’m more surprised that common knowledge is not so common but yet its value is actually beyond what I can imagine. Pinker does such a good job of conveying its importance.

A wonderful read!
This novel drew me in from the very first page and kept me hooked until the end. The characters were vibrant and relatable, the writing was engaging, and the story had just the right balance of heart and humor. Highly recommend!
Many thanks to NetGalley, the author, and the publisher for my ARC. All opinions are my own.

It’s all about how we understand what other people are thinking—and how we think about what they think we’re thinking. Sounds tricky, right? But Pinker makes it super interesting and easy to follow. I did t realize how understanding this affects everything from money and power to everyday life.

If you’ve enjoyed Steven Pinker’s other books, like The Sense of Style or The Stuff of Thought, you’re going to love this one. He’s amazing at teaching about language and how we communicate, and this book takes it to a whole new level. It’s packed with cool examples, like why we blush or laugh, and how we use signals to connect with others. You’ll start noticing these things everywhere once you read it. It’s a fun and eye-opening book that’ll make you see the world in a totally new way!

To be fair, I only made it through two chapters. I read Pinker's "The Language Instinct" a long time ago and liked it a lot. This book was very difficult going -- muddy, confusing, and to me felt like he was having trouble defining what felt like a pretty basic concept. I lost interest. It could very well be that I'm just not up to the task, so your mileage may vary!

A fascinating exploration of thinking and common knowledge. It is a dense read but the author deftly incorporates anecdotes, illustrations, and humor to help convey his points. If you enjoy thinking about thinking, and you wonder why people are so often unable to clearly communicate their thoughts, give this a read!

Thank you to Scribner and NetGalley for the opportunity to read a copy.