Today we're going to talk about common knowledge, not the a little club soda will get that stain out kind.

But awareness of someone else's awareness of something.

As in I see that you have a stop sign, and I know that you see that stop sign, and I know that you know that.

I know there's a stop sign right there so I can drive through this intersection, trusting that we will not crash that kind of common knowledge from KERA in Dallas.

This is think I'm Chris Boyd.

I realize it doesn't exactly feel like we've worked out the relativity of space and time here, but once you start paying attention to the role common knowledge plays in virtually every human interaction, you realize that without this amazing ability, society as we know it could not exist.

Steven Pinker has been paying attention.

He's devoted much of his career to thinking through how we think.

He's the Johnstone Professor of Psychology at Harvard, and his newest book is called When Everyone Knows That Everyone Knows common knowledge and the Mysteries of money, power, and everyday life.

Steven, Stephen, welcome back to thank.

Thank you.

How does the story of the Emperor's New Clothes illustrate how common knowledge works?

When the little boy said the emperor was naked, he wasn't telling them anything they didn't already know.

But he changed the state of their knowledge nonetheless.

Because after he blurted it out with an earshot of the of everyone else, now everyone knew that.

Everyone else knew that.

Everyone else knew that the Emperor was naked.

And that's a different state of knowledge than just knowing it.

Knowing that is knowing that everyone else knows it now.

And of course, the crucial punchline to the story is that changed their relationship with the editor or with the Emperor from.

From from obsequious deference to ridicule and scorn.

And so the the morals of the story of that story, at least as the way that I interpret it is, first of all, that there is a big difference between everyone knowing something and everyone knowing that everyone knows it.

Second, that that mind bending state needn't actually consist in anyone's consciousness of.

I think that he thinks that.

I think that he thinks that.

I think that he thinks because you can start to get dizzy after a few rounds of that.

And technically, in the logicians understanding of common knowledge actually has to be an infinite number of I know that he knows that.

I know that he knows, which is of course can't fit inside a finite head.

So the second moral of the story is that a conspicuous, self-evident event, something that happens when you see everyone else seeing it happen, can generate common knowledge in a stroke.

You don't have to actually go through the thoughts of, I know that she knows.

You just know it instantly by the fact that it is public conspicuous out there.

Then the third moral is that common knowledge matters to our social relationships.

In this case, The deference and respect that the Emperor had previously commanded.

Shattered by the the common knowledge of his of his dignity, that has big ramifications that we will be talking about later in this conversation.

Yes.

Well, more generally in the the academic literature on common knowledge, the, the mathematicians, the logicians, the philosophers, the economists, the understanding is that common knowledge is necessary for coordination, for people being on the same page, acting together in a way that benefits everyone.

You can't do it if you're the only one doing it.

If you don't know that everyone else knows that that's the way to do it.

A very simple example is driving on the right as opposed to driving on the left.

There's no reason to drive on one side over the other, but there's every reason to drive on the same side that everyone else is driving.

And everyone has to know that.

Um, And but what I argue in the book, which is a novel contribution, is that our social relationships, like deference and respect, friendship, communal warmth, love, a sexual relationship, a transactional relationship where you're simply exchanging things.

All of these are cemented by common knowledge, too.

They all involve coordination.

What makes two people friends?

Well, each one knows that.

The other one knows that.

The first one knows that their friends.

It's not as if they sign a contract.

But that's the way our social relationships work as well as our formal relationships, like traffic laws, like using paper currency, like respecting who's the the boss or the president or the king and so on.

So how is common knowledge different from what's called private knowledge, which can be termed private even when it is widely shared among people?

Yes.

Well, well, let's go back to the Emperor's new clothes.

The.

When the Emperor paraded around, there was universal private knowledge.

Everyone knew that the emperor was naked privately.

They couldn't be sure that everyone else knew that, because, of course, everyone.

The story had gone around that only fools could fail to see the Emperor's new clothes.

And so no one wanted to admit they were a fool.

They still had to harbor, at least within the suspension of disbelief in the story.

Had to harbor some doubt as to whether they were the the only one.

But that was exploded when there was the public signal of the little boy blurting it out.

So I've been in conferences where I've been a little bit bored by whatever's taking place on the dais, and assumed that I was the only one, because we're all sort of leaning forward and performing our attention.

That's private knowledge, even if we all sort of share the same observation.

Yes, and sometimes there can be a combination of private knowledge and public misconception, sometimes called a spiral of silence or pluralistic ignorance, where everyone mistakenly thinks that everyone else believes something and no one actually believes it.

It was, I think, the first study of it was done in a fraternity, where it turned out that none of the the the frat bros.

Actually thought it was cool to to to drink until you pass out, but each one felt they had to do it because they mistakenly thought all the others thought it was cool.

Um, and there are many other examples in Saudi Arabia.

It turned out that none of the men actually thought that women should be kept in the home and forbidden to work or drive, but none of them would allow their wives to work or drive, because they mistakenly thought that all the other men thought that that all the other men thought it was unacceptable.

Wow.

You mentioned cooperation and the fact that common knowledge is really important for this, or rather coordination.

I wanted to ask you if we need to make a distinction here between cooperation and coordination, when we consider the role of common knowledge.

Well, I make the distinction.

It's not a technical one.

It's not common knowledge, you might say, but cooperation, as it's been discussed in, in biology, in sociology, in books like The Selfish Gene by Richard Dawkins, referred to the case in which someone or several people pay a cost in order to benefit someone else.

So animals that take turns grooming each other or feeding each other, people who trade favors are raising the question of how can you be sure that you'll be paid back?

And if you aren't, why are people nice to each other?

Why do they give blood, give to charity, and so on?

And it's a fascinating problem.

But it's not the only problem of people working together, because sometimes people work together and for everyone's benefit and no one pays a cost.

In the animal kingdom, we sometimes call it mutualism.

So when an ox or bird picks ticks off the back of a of a zebra, um, it's not a it's not as if the speaker is doing the zebra favor and expects to be repaid.

It's that it's for the speaker's own good.

It gets a meal for the ticks.

The zebra gets something out of it.

It's tormented by by fewer pests.

And as we say, everybody wins except the chicks.

But the.

So that's a case of coordination or mutualism in the animal kingdom.

Namely you deliver a benefit to another organism at the same time as you are enjoying a benefit yourself.

So it's in everyone wins type of situation where it doesn't raise the puzzle of why would anyone bother?

Why is it everyone selfish?

But it is a question of coordination, of information.

Being on the same page.

Avoiding clashes.

Avoiding too many cooks.

Avoiding things.

Falling through the cracks.

Each one has to know that.

The other one knows that they know that the other one knows.

In order for them to be on the same page and act together.

If we didn't have this somewhat miraculous ability to instantaneously work out what is common knowledge in many situations, we could just establish this using language, right?

Do you see that stop stop sign?

I see that stop sign.

That's less efficient in a lot of situations.

Is that the problem?

Well, I think language, the reason that we, even our species has language is to in large part to generate common knowledge.

So, so that we can coordinate.

Um, you, um, you guys fan out on the East?

We'll fan out on the west.

We will trap the animals at the edge of a cliff where we can easily dispatch them.

Uh, you can't do that if each one is marching to the beat of his own drummer.

And, um, it's even hard to do with with gestures, but with language, uh, you know that the other person has understood what you said, and they know it, and it allows you to act together so language can generate common knowledge.

It's not the only thing.

There's also eye contact.

There's also laughter.

There's also blushing.

There's also tears.

Uh, but it is a way of generating many, many different kinds of common knowledge very, very effectively.

So I think it's not a coincidence that we are the species that has language.

We're also the species that does big, impressive things.

We build things.

And perhaps the story of the Tower of Babel is a story about the common knowledge generating power of language that as long as everyone spoke the same language, they could build a tower that would reach up to the heavens and threaten God himself once they lost that ability to coordinate by the.

Each speaking a different language, they lost the ability to coordinate.

We're learning more and more as time goes by.

About at least rudimentary capacity for something like language in other species.

But as far as we know, how common is it for social animals to verify and demonstrate common knowledge?

There are certain hardwired ways in which they can do it, where there is some public signal that they can all perceive at the same time, that can get them all on the same page.

So I give the example of what what a marine biologists call the Great Barrier Reef Annual Sex Fest, which is less racy than it sounds because it doesn't pertain to people.

It pertains to coral.

Now, the coral have this problem.

They they're stuck to the the ocean floor.

They can't get around.

And so how do they how do they mate?

The answer is they spew eggs and sperm into the water.

As if hoping that they will meet their counterparts spewed up by some other coral.

But they can't spew their gametes 24 over seven.

That would be, you know, expensive, exhausting.

Ideally, they would all agree on what day of the month, what day of the year to, to, to to spread the gametes.

And they do they coordinate on the full moon.

They fixed number of days after the full moon.

They all spew simultaneously.

And in a sense, in a kind of metaphorical sense.

They have common knowledge that that the five day say after the full moon is the day to do it.

Now they don't literally have knowledge because they don't even have brains to have knowledge with, but they have the implicit equivalent.

Now, what makes humans different is that we do actually think about what other people think, about what we think about what they think.

And so we're much more flexible.

It's not just a question of of having sex five days after the full moon, but there's no limit to the number of ways in which we can coordinate.

We can use pieces of paper as sources of value, namely currency.

We can all respect the same leader, chairman or president or king.

We can drive on the right or drive on the left.

We can stay home on Sunday.

All of these things where there's no particular reason to do it that way, other than that everyone else is doing it that way, which is reason enough as long as everyone knows that everyone knows it.

And even the most fractious and disagreeable among us engages in a lot of common knowledge activity every day.

Yes, when we whenever we use direct language, whenever we make eye contact, whenever we use some understanding to show up at a particular time, whether it's for a bee, for a rendezvous, or showing up for work.

Whenever we recognize people as, say, committed versus available, that's why we have weddings.

It's a common knowledge generator.

When you're at a wedding, you.

That's the moment everyone knows.

That's the moment you see other people witnessing the event and witnessing you witnessing it.

Many of our ceremonies are rituals.

Our symbols are arbitrary, but not kind of random.

They are arbitrary, but they have a logic to them in that everyone recognizing the same arbitrary point allows you to coordinate.

Why does the week have seven days?

There's nothing about seven that corresponds to any astronomical event or any natural cycle.

But once seven days got locked in with the Babylonians, you have to have some sort of cycle.

As long as everyone agrees that it's seven, it works for everyone.

Stephen, you've referred to currency a couple of minutes ago.

You write in the book that common knowledge can create nonphysical realities.

So how did common knowledge free us all from having to walk around if we wanted to go to the market with pockets full of silver and gold?

Yes.

Right.

And or bartering chickens for.

For wool or pockets full of chickens.

Right.

So what makes it is a fact that a dollar is a carries value.

But where is that fact?

I think some people might think, well, don't they have like a bunch of gold in Fort Knox?

But you know, we're not on the gold standard anymore.

The reason that money is indeed valuable is that everyone knows that it's valuable, but more important, everyone knows that everyone knows.

So I can give up something of value for a green piece of paper, because I know that other people will accept it because they know that still other people will accept it.

Conversely, if that common knowledge Evaporates.

If people no longer trust in the currency, then you can very quickly get hyperinflation and the currency can become worthless.

So realities like institutions, corporations, governments, universities, non-profits, um, entities like days of the week, um, are exist even though they're not made of stuff.

Uh, you know, there's no such.

You can't go looking to find where Tuesday is.

Uh, but Tuesday is real because everyone knows what what Tuesday is.

And everyone knows that.

Everyone knows.

So common knowledge can generate social realities which can govern, govern our lives.

And they can, especially when it comes to things like authority.

Who has, uh, who has power?

Uh, it's you might think, oh, well, the people with guns, but it's not exactly right, because no regime has enough, uh, firepower to intimidate every last member of the of the population.

If everyone decided to storm the palace palace at once, no government on earth could stop them.

Or if they all decided to stop working on the same day until they the the, the government left.

That's why you often have regime changes when there is a public demonstration where everyone shows up and everyone sees everyone else showing up, that can give you the safety in numbers.

As long as there is coordination, which you can only have through common knowledge.

In this case, people who might privately have been discontent with the regime, each one fearing either they might be the only one, or even suspecting that other people were discontent.

Discontented, they may not know that the others knew that others were like them.

That can change if you've got either a public media like like a printing press.

That's why dictatorships don't have freedom of the press or a public turnout in a in a public place where everyone can see everyone else.

And that's why dictatorships don't have freedom of assembly.

The story of the Emperor's New Clothes demonstrates that common knowledge isn't necessarily always accurate or true fact.

How do our affiliations and relationships shape our perception of common knowledge?

Just take the two main political parties in this country.

They seem to be looking at very different realities, but within those parties, those realities are agreed upon.

Yes.

So common knowledge is often generated by salient public signals, things that everyone can see while knowing, seeing that everyone else sees them.

And it's possible that we had less polarization in the past because we had more nationwide media.

Everyone watching Walter Cronkite on the on the CBS news, or everyone even listening to Johnny Carson or reading USA today or listening to to watching CNN.

With the rise of cable news networks like Fox News, which appeal to an audience of, um, uh, a subculture where, uh, everyone gets their information from the same source, which might be completely walled off from other sources of information, social media.

It has been shown that people tweet and retweet or post and a repost or link and relink within interconnected networks that may have very few links to other interconnected networks that connected within themselves.

But there are not very many bridges from one to the other, and that can lead to separate pools of common knowledge.

More accurately common belief.

Because technically something has to be true for it to be knowledge.

So if different communities believe different things, they can't both be right.

So you might call it common belief, but it's the same kind of phenomenon.

How does common knowledge play into the modern day phenomenon of cancel culture?

Well, in cancel culture, where you can get a mob falling over each other to denounce some, um, some some sinner, some miscreant, I think in the case where norms are propped up by common knowledge, that is what, um, uh, norms like, which can change.

Like you don't tell ethnic jokes in public anymore.

You pick up after your dog.

Uh, you don't smoke indoors.

Uh, they exist because everyone knows they exist, and therefore if someone flouts them in a public manner where you fear that everyone sees them floating it, then the norm itself can unravel.

Unless the norm breaker is publicly punished.

And again, it has to be public.

Now, in the old days, punishments were public, yet public hangings.

You had pillars and stalks in the town square.

You had burnings of the stake and crucifixions and and so on.

Now we do it through, through the media.

But the general dynamic that to hold up a norm, the norm breaker has to be publicly punished.

Is something that we see, I think, playing out in shaming mobs in cancel culture, where someone who is thought to break a norm, they make a remark that other people interpret as as racist or as condoning violence against their side.

Aside, the people feel the urge to rise up and punish them publicly.

Or better still, silence them deeply for them, as we say.

An interesting metaphor because a platform generates common knowledge, someone on a platform can be seen by a crowd, each of whom sees the other.

And so, to prevent the dangerous idea or the flouting of the norm for becoming common knowledge, you take them off the platform.

Any sense of why?

Some people seem very motivated to sort of perform this excoriation of people who have broken norms, and other people may silently disagree but not feel the need to say pile on on X or some other platform.

Well, there are some of it as individual differences in just in terms of how sadistic people are.

And it has been shown that the social media mobs often tend to be by independent measures, Uh, people who are who take enjoyment in other people's pain.

Sadists.

Um, there's also, though, um, the a general problem is when when something has to be done for the public good and whoever does it take some risk at paying a price.

Who's going to volunteer?

There's the old story of who will build a cat, where the mice will all be better off if someone puts a bell around the cat while it's sleeping, so that when the cat approaches, they bring you the bell alerts the mice.

But of course, whichever mouse tries to put the bell around the cat's neck has some chance of being eaten if the cat awakens.

So the who will bell the cat problem, sometimes called the volunteers dilemma uh sometimes is solved by showering praise kudos rewards on the the person who, um publicly makes the sacrifice on behalf of the group, and indeed, people who publicly punish are sometimes rewarded in esteem and opportunities for cooperation by the rest of the community.

Why are we so good at noticing the hypocrisies and the inaccuracies of people outside our own group?

Assuming that those people don't have any logic, they don't apply reason to their values and therefore at the same time rather so blind to the ways that our own group may have similar flaws in our thinking.

Yes.

And I think there's there a biblical passage that you.

Note the mote in someone else's eyewall, ignoring the plank in your own right.

Um, yeah.

So it is a widespread human bias, sometimes called the my side bias to assume that your own code.

You yourself and your own coalition, your tribe, your political party, your religion are wise, knowledgeable, rational, noble.

And the other side is ignorant, stupid, selfish, evil.

Now, not everyone could be right.

And and the polarization is largely a phenomenon of negative polarization.

It's the my side bias going out of control.

Um, the one of the reasons that, uh, exchange bringing people together diversity of viewpoints, free speech is essential is that it is one way to push back against the my side bias.

If someone can say something and someone else has the freedom to say what's wrong with it, then there's at least some chance of breaking out of your bubble of misconceptions.

So this is why authoritarian leaders really don't care for free speech.

They don't care for it.

Indeed you might.

It is something to to think about.

You might think, well, you know, why doesn't an autocrat just let the people bitch and moan all they want?

I mean, he's got the guns, but the reason is that when people with free speech, um, freedom of the press, even even more so, there is the means to generate common knowledge that people can coordinate on their opposition to the regime.

If they act together, they can sometimes bring about regime change in a way that if they acted at separate times, the regime could pick each one of them off individually.

So I tell I recount the joke from the Soviet Union, of course, a totalitarian state of man distributing leaflets in Red square.

And of course, the KGB immediately arrest him, bring him back to the police headquarters, only to discover that he's been handing out blank sheets of paper.

They confront him, they say, what's the meaning of this?

And he says, what's there to say?

It's so obvious.

So that's a joke about common knowledge.

He wasn't conveying any particular content.

But as with the little boy in the story The Emperor's New Clothes, he was changing people's state of knowledge, namely everyone who saw him and accepted the piece of paper and saw other people accepting the paper knew that the source of disgruntlement, the grievance was common knowledge, and that could allow people to coordinate their opposition, which is far more effective than opposing the regime individually.

And the reason?

Oh please continue.

Sorry.

The reason it works to to take another allusion from popular culture in the movie Gandhi, the Gandhi character at one point says to a British colonial officer, in the end you will leave because there is no way that 100,000 Englishmen can control 350 million Indians if the Indians refuse to cooperate.

He might have said, unable to coordinate.

I think what's so interesting about the, you know, anecdotes about an autocrat not wanting people to speak freely about their discontent is that presumably those autocrats are aware that people may not love every policy.

Some of them, you know, they have the ability to sort of suss out common knowledge as well as anybody else.

They're okay with people thinking it as long as they don't dare say it.

Yes, as long as they well, as long as they don't say it within earshot of everyone else.

Right, right.

They, um.

And I cite a study done by my colleague at Harvard, Gary King, on censorship in China, where they got a trove of millions of social media posts and also were able to figure out which ones were being censored.

And it turns out that, um, complaining about a government official, uh, is not necessarily, um, censored.

Uh, in fact, the Chinese government kind of values that as a source of information about which government officials aren't doing their jobs.

They're kind of modifying the masses.

But anything that hints at coordination a meet up, a new bulletin board, a new social media group where someone might share their discontent in a way that other people can find out about it, or where people can form some group, some organization.

Chinese government clamp comes down on that like a ton of bricks.

It's the coordination that they are afraid of.

You note in the book that we don't come into the world with the ability to figure out what is common knowledge.

This ability develops around age 7 or 8.

So is this something we learn or something that is a product of our brain development at a particular time?

Well, what happens at 7 or 8 is that is the ability to think about thoughts, about thoughts that starting around 3 or 4 kids can appreciate that other people have beliefs and desires, but the idea that they might have beliefs and desires about other people's beliefs and desires come, comes a bit later.

And in general, the more layers of thinking about other people, thinking about your thinking about their thinking, about your thinking and so on, it is mentally strenuous for, for, for.

For the best of us.

The most mature of us.

And it, uh, it matures through, through life and it varies among people.

People with more social skills, more savoir faire, more social insight.

Less likely not.

Not not along the spectrum, as we now say, have more of an ability to think about thoughts, about thoughts.

But the just the ability to leap to the state of common knowledge.

Sometimes we can leapfrog all of the.

I think that the thing that she thinks if there is a Conspicuous public signal and kids earlier on are um.

Do have common knowledge of some conspicuous events like, um, as joint attention.

If you're looking at something that your parent is looking at and you, each of you can see the other looking at it, that is a kind of common knowledge.

It's necessary for kids to learn words, because words only work because they're common knowledge.

Uh, what makes the word rows refer to arose?

Shakespeare said by any other name, it would smell just as sweet.

Rose means rose because everyone knows that.

Everyone knows that it means rose and kids, early on, if you teach them a new word, they'll immediately use it with third and fourth and fifth parties, even though they don't have any direct evidence that other people use the word the same way.

That just built in that words are conventions that work through common knowledge without having to think through all the layers.

Likewise, laughter kids don't like being if everyone starts laughing at them eye contact, they a misbehaving child, will avoid making eye contact with their parents so that even if they're misbehaving, they're not misbehaving and defying their parents, which is two infractions rather than one.

So they must have some sense that eye contact can generate common knowledge.

Namely, you know that you're being a bad kid and define your parents when you make eye contact.

Stephen, this ability to think about thoughts, about thoughts, this is what's called recursive mental izing.

Well that's the jargon term.

Yes.

So mental izing means getting inside someone else's head, trying to figure out what they're thinking.

Recursive mental izing is recursive means contains an example of itself, or you're taking it to the next level where recursive mental ising was thinking about what someone else thinks about what someone else thinks.

How did recursive mentalism deliver us a toilet paper shortage during the pandemic?

Yes.

So, uh, one of the indignities the Covid pandemic was that, uh, toilet paper was, uh, in short supply, largely because, uh, and it wasn't actually in short supply until people thought it was in short supply.

The the manufacturers of toilet paper quickly stepped up the manufacturing when people started staying home and were using the big jumbo rolls at schools and offices.

But there was no problem to generate more, um, bundles of Charmin.

Uh, but people started to worry that other people were worrying that other people were worrying.

And so no one wanted to be left going to the supermarket or drugstore and finding the shelves bare.

It's just like what happens during a bank run, where as soon as there's a rumor that the bank might be in trouble, whether or not it is in trouble, people might withdraw their savings out of fear here.

They do really do engage in recursive mental izing.

They think, oh geez.

Well, it seems to me the bank is okay.

But you know what if what if the other guy thinks that the bank is in trouble and he may not even think the bank is in trouble, except that he's thinking that someone else will think that the bank is in trouble.

And in fact, if everyone were to withdraw their savings at once, the bank couldn't cover everyone's deposits and the bank could fail taking the economy down with it.

And that's what happened during the Great Depression.

So when Franklin Roosevelt said, the only thing we have to fear is fear itself, he was stating a truth about common knowledge that was really true, that the fear caused the fear caused the Great Depression, which is why these panics can sometimes be nipped in the bud by some signal that no one can act on their fear.

In the case of Roosevelt, it was the bank holiday for a weekend or in a couple of days.

The banks were known to withdraw their money, and that meant that no one had to worry about other people withdrawing withdrawing their money.

In the case of the toilet paper shortage.

Grocers started to post signs saying limit three rolls per customer.

And that ended the shortage.

Not so much because people couldn't buy more than three rules.

But people no longer had to worry about other people by hoarding.

And according to one story, this all began with an act of generating common knowledge, which was a comedy monologue by Johnny Carson in the era in which The Tonight Show was watched by a huge segment of the American population.

There are only three commercial networks.

Carson was the king of late night, and if he said something, you had reason to believe that a lot of other Americans were listening to him, and that they knew that a lot of Americans were listening to him.

So one night in I think 73.

The, um, after the, uh, the, the Arab oil embargo, there were some shortages of meat.

And, uh, Carson quipped, you know, we've had all kinds of shortages these days, but here the latest I read it in the papers.

There's a shortage of toilet paper.

Now, it turned out there wasn't a shortage of toilet paper, but then there was a shortage of toilet paper.

When everyone who watched Johnny Carson or knew that a lot of other people were watching Johnny Carson, worried about a toilet paper shortage, ran out to get toilet paper, creating a toilet paper shortage.

The man did not know his own power to create.

He may not have known.

Indeed.

Well, and some people who do know their own power, such as the chairman of the Fed Federal Reserve Board, know that.

Financial panics, bank runs, currency attacks.

Recessions can happen when there is the fear of fear itself.

And so they watch their words very carefully.

Anything think indication from the fed that there may be a possibility of a recession can cause a recession as people put off purchases, as manufacturers cut back on manufacturing or refrain from hiring people.

Which is why I quote from Alan Greenspan.

Greenspan.

Since I become a chair of the fed, I've learned to mumble with great incoherence.

If you think that I've been clear, you misunderstood what I said.

I remember people used to watch even Alan Greenspan's briefcase, and whether he carried a thin briefcase or a fat briefcase into meetings to try to predict what he was going to say.

Now, the chair of the Federal Reserve does have real and consequential power.

How does common knowledge grant power to entities that really have only soft power and frankly, no teeth like the International Criminal Court?

Yes.

So sometimes there are many, um, court systems, like rabbinical courts and sharia courts and councils that have no teeth.

But that can be very effective because they generate, uh, common knowledge focal points.

So and in fact, even, um, the, the, uh, the law of the land and the court system, they just aren't enough, you know, informants and security cameras and police officers and court time to haul everyone who breaks a law into court.

Uh, the reason that the law can be effective is that everyone knows that that that, uh, what it is.

And so in certain confrontations, one person will back down and the other will get his way.

Why?

Well, the person who backs down backs down because he knows the other will stand his ground.

And the guy who stands his ground stands his ground because he knows the other will back down and so on and so on and so on.

How do they get to that state?

Well, if there is a public rule or law.

That's where they can agree who stands as ground and who who backs down.

It's sometimes called the expressive power of the law.

And I give the example of a transition that I lived through in college, where the people used to smoke in classrooms, professors which would chain smoke through lectures, even in small seminar rooms, students would would light up next to each other in an electron.

It was really awful for a nonsmoker like me, but I always had to be afraid in asking someone to put out their cigarette.

What if they made a scene?

What do they said?

I have the right to smoke.

Who are you to tell me not to smoke?

Uh, as soon as university started to post no smoking signs and made it be known that that was the policy, even though I don't think, you know, there was no, you know, smoking snitch ER's hotline, there were no smoking police.

But when I tapped someone on the shoulder, I could point to the the no smoking sign.

And what it meant was, if one of us has to back down, it's the smoker.

How does common knowledge play into the esteem we give someone who has made a charitable gift, depending on whether or not they make this very publicly or very privately.

It's the the way that I first became aware of the phenomenon of states of mutual knowledge and how potent they could be in human affairs.

So in charitable giving, there's a, a paradox that, um, the, uh, a donor who, uh, someone who very generously gives money if it is known that he, he, uh, he money people sort of suspect him as maybe being in it for the reputation as having the ulterior motive.

Um, on the other hand, you know, a lot of people probably wouldn't give unless they were incentivized by a reputation for generosity.

And I learned about it in Sunday school when I learned about the great Rabbi Maimonides, Moses Ben Maimon, who in the in 12th century Islamic Spain came up with a hierarchy, a ladder of charity, or more accurately, a ladder of righteousness.

Tzedakah, where the righteousness of a gift did not just depend on the size of the gift, but on the status of knowledge of the giver and the recipient.

So high up in the ladder was a double blind donation.

The rich person gives money in a community chest.

The poor person retrieves the money from the chest.

The beneficiary doesn't know the donor or vice versa.

That was very close to the the highest level.

The lowest level was common knowledge.

The donor puts money into the hand of the recipient.

Each one knows who the other is.

Then there are intermediate rungs like the donor knows the beneficiary, but not vice versa.

Like you leave some food on the doorstep of a poor person in the dead of night.

Scurry away.

They next morning they opened the door and they have the food package.

The donor knows the beneficiary, but not vice versa.

That's not as good as the double blind gift in a community chest.

And one rung down from that is when it's the other way around.

So a wealthy person walks around with cash in a backpack.

The poor person can pick it out with the.

Scent, but not the knowledge of the donor.

So the beneficiary knows the donor, but not vice versa.

And even as a child, I wondered, why does that?

Why should that make a difference if you're a poor person?

You know, money is money.

Food is food.

Who cares whether the donor is known or not?

Or the beneficiaries know the the analysis that.

That we came up with.

Me and some students researching the phenomenon is that with a that we're always on the lookout for who is just intrinsically dispositional in the marrow, generous, who gives what they more than what they have to.

Um, we want to hang out with people like that.

Those are those are those are people who might be good for us.

Someone who gives and could call in the favor, could enjoy a reputation for giving, probably isn't quite as generous as someone who is willing to give anonymously.

They must be truly generous if there's nothing in it for them.

And the.

I note that the.

This paradox was explored later by another great Jewish thinker, Larry David, in an episode of Curb Your Enthusiasm, which works at The Paradox, where Larry Larry's character donates money for the wing of a nonprofit which is named after him.

The other wing, uh, there's an inscription donated by anonymous, but it leaks out that the donor was his rival, Ted Danson.

And everyone is gushing over what a great guy dancing is.

He gave all this money, and he didn't even care about the credit.

Of course he was getting the credit, but the credit wasn't common knowledge.

Everyone knew, but everyone did.

No one knew that.

Everyone else knew.

And so he got the, uh, both the, uh, reputational boost from the gift and, paradoxically, from the anonymity.

How does common knowledge play into plausible deniability?

Like if we get pulled over and we're tempted to bribe a police officer rather than get a ticket on our credit, on our our driving record?

I think what happens there.

This is the phenomenon that got me interested in this common knowledge in the first place, through my interest in language where we use euphemism and innuendo and hints and winks and we beat around the bush, and we surely shall be kind of hoping that the listener will catch our drift is that it's not so much plausible deniability.

So if you, uh, if someone says, do you want to come up for Netflix and Netflix and chill?

Um, you know, I think the plausibility isn't that deniable.

I think any grown woman knows what that means or gee, officer, or is there some way we could settle the ticket here without doing a lot of paperwork?

You know, how plausible is the deniability?

And we've done the studies.

And the answer is not not plausible at all.

However, what is plausible is deniability of common knowledge.

That is, she could think, well, maybe he you know, I know that he's just, you know, invited me up for sex and I've said no, but does he know that?

I know, maybe maybe he thinks I'm naive.

And he could think, well, does she know that?

I know, maybe she thinks I'm dense.

So even if there's no deniability that a sexual proposition was tendered and refused, there could be deniability of the common knowledge.

And, crucially, the reason that people go through this ritual is that that can preserve their relationship.

They can continue on as if they were platonic friends, as if they were supervisor and supervisor, by denying that each one knows that they know, allowing them to carry on the fiction of their former previous relationship.

Stephen, before I let you go, is there anything we can do with what you've taught us today about common knowledge that will help us interrogate our own beliefs about the world?

Well, we can become aware of when we are deliberately keeping some fact out of common knowledge.

We're relying on innuendo or hypocrisy or politeness because it preserves a relationship.

And perhaps sometimes a relationship has to be changed.

One person is always getting the short end of the stick, and they have to say that, uh, you know, perhaps rudely, uh, object the way they're treated.

I think that sometimes our relationships are really valuable and it is worth the art, the social skill, the tact of conveying something without generating common knowledge.

Steven Pinker is the Johnstone professor of psychology at Harvard University.

His newest book is When Everyone Knows That Everyone Knows Common knowledge and the mysteries of money, power, and everyday life.

Steven, thanks so much for making time to talk.

Thanks for having me.

Thank you.

Distributed by PRX, the Public Radio Exchange.

You can find us on Facebook, Instagram, anywhere you get podcasts and at Think Again, I'm Chris Boyd.

Thanks for listening.

Have a great day.