Speaker 1: Why do people speak in innuendo when they're on a date.
Speaker 1: Why do dictators try to squelch protests, Why do we
Speaker 1: join up with bullies to gang up on an outcast.
Speaker 1: Why do humans stand out from the rest of the
Speaker 1: animal kingdom by blushing and laughing and crying? And what
Speaker 1: does any of this have to do with George Costanza
Speaker 1: or when Harry met Sally, or anonymity on social media
Speaker 1: or cancel culture, or why we generally don't say everything
Speaker 1: we mean. Welcome to Intercosmos with me David Eagleman. I'm
Speaker 1: a neuroscientist and author at Stanford and in these episodes
Speaker 1: we sail deeply into our three pound universe to understand
Speaker 1: why and how our lives looks the way they do.
Speaker 1: Today's episode is about a phenomenon known as common knowledge,
Speaker 1: which is something that I know and you know, and
Speaker 1: we both know that we know it. Now, this could
Speaker 1: seem like a very particular sort of thing to pay
Speaker 1: attention to, but many psychologists and economists over the past
Speaker 1: decades have started to think that a deeper understanding of
Speaker 1: common knowledge could explain all kinds of things about human
Speaker 1: nature and behavior and societies, and for a very long time.
Speaker 1: This has grabbed the attention of my friend and colleague
Speaker 1: Stephen Pinker, who just this week has a new book
Speaker 1: coming out on common knowledge called When Everyone Knows That
Speaker 1: Everyone Knows, And so I called him up to discuss
Speaker 1: this topic. I'll take just a moment to frame this
Speaker 1: before I begin the interview. At the heart of the
Speaker 1: issue is that we are a massively social species. We
Speaker 1: form lifelong relationships, and we join clubs, and we're parts
Speaker 1: of tribes, and we're citizens of countries. And we're also
Speaker 1: a highly intelligent species, and we spend a lot of
Speaker 1: our time, usually unconsciously, figuring out who knows what and
Speaker 1: what we know in common, and for that matter, thinking
Speaker 1: about how we can expand common knowledge with the right signals,
Speaker 1: and often how we could hide things from becoming common knowledge.
Speaker 1: The key thing to understand for today's conversation is that
Speaker 1: common knowledge is not just about a bunch of individuals
Speaker 1: each knowing something. It's that each person knows it and
Speaker 1: knows that everyone else knows it, and knows that everyone
Speaker 1: else knows that they know it, and so on. And
Speaker 1: the argument is that it's this ladder of shared awareness
Speaker 1: that allows societies to coordinate. Think about something like the
Speaker 1: game of chicken, where two drivers speed towards each other.
Speaker 1: Each knows the situation, but the critical factor is whether
Speaker 1: both drivers know what the other is willing to do,
Speaker 1: and whether both know that the other knows. And the
Speaker 1: effects of common knowledge stretch from two people all the
Speaker 1: way up to countries. For example, history is filled with
Speaker 1: moments when private thoughts turned into common knowledge and changed
Speaker 1: the world. So, for example, in nineteen eighty nine, East
Speaker 1: Germans had long doubted the regime, but it was only
Speaker 1: when tens of thousands gathered in the streets when everyone
Speaker 1: could see that everyone else had the same doubts. That's
Speaker 1: when the Berlin Wall fell. Stock Market bubbles and crashes
Speaker 1: run on the same sort of principle. Investors don't care
Speaker 1: only about the value of a stock, but about what
Speaker 1: everyone else believes everyone else believes about its value. So
Speaker 1: this is the type of thing that Pinker's book explores,
Speaker 1: all all the ways in which common knowledge permeates everyday life.
Speaker 1: Common knowledge, for example, is why etiquette works. You don't
Speaker 1: just know the rules, you know that others know them too.
Speaker 1: It's why red lights function not because you fear the police,
Speaker 1: but because you know that everyone else knows the rule
Speaker 1: and is going to stop. It's why children learn to
Speaker 1: play Peek a boo, because the delight comes from that
Speaker 1: shared loop of I know that, you know that I'm here.
Speaker 1: So today we'll explore the phenomenon of common knowledge. Stephen
Speaker 1: Pinker is a cognitive scientist and linguist at Harvard and
Speaker 1: he's a longtime bestselling author who is famous for illuminating
Speaker 1: the hidden structures of human thought and society. His new
Speaker 1: book dives into the puzzle of common knowledge, how it arises,
Speaker 1: why it matters, and what it reveals about the architecture
Speaker 1: of our social minds. Stephen joins me, Now, so, Steve,
Speaker 1: we are an intensely social species and there's a lot
Speaker 1: that has to happen in order to get us to
Speaker 1: coordinate as a result. And this is the thing you've
Speaker 1: been thinking about, So tell us how do we coordinate
Speaker 1: as a species.
Speaker 2: Well, any two agents who need to coordinate need common knowledge.
Speaker 2: The theme of the book, common knowledge, being the state
Speaker 2: where I know something, you know it, I know that
Speaker 2: you know it, you know that I know it, I
Speaker 2: know that you know that I know that you know it,
Speaker 2: ad infinitum. Why Because it isn't enough for each party
Speaker 2: to know what the other one is going to do,
Speaker 2: because the other party guessing what the first one is
Speaker 2: going to do may do something complete different. So just
Speaker 2: be concrete. If we're going to rendezvous and we don't
Speaker 2: generate common knowledge by a conversationalist, and my cell phone
Speaker 2: goes dead, so each of us asked to guess where
Speaker 2: the other one is going to go. It's not enough
Speaker 2: for me to know that you like to go to Starbucks,
Speaker 2: because you may know that I like to go to Pete's.
Speaker 2: And so if I go to Starbucks, that's where you're
Speaker 2: going to go. You might go to pizza because you
Speaker 2: think that's where I'm going to go. And well, I
Speaker 2: know that, okay, so I'll go to Pietz because Dave
Speaker 2: knows that I like to go to pizza. But wait
Speaker 2: a sec Dave knows that I know they likes to
Speaker 2: go to Starbucks, so he's going to go to Starbucks
Speaker 2: after all, and so on. Nothing short of actually blurting
Speaker 2: it out in each other's presence will get you on
Speaker 2: the same page. Some kind of public perceptible self evidence signal.
Speaker 2: That's what is needed for coordination.
Speaker 1: You've, of course spent much of your career studying language,
Speaker 1: and so you see language as one way of establishing
Speaker 1: that common knowledge give us a sense of that, Yeah,
Speaker 1: you know that.
Speaker 2: I'm trying to get you to believe something because you
Speaker 2: know that I'm saying something with the intent that you
Speaker 2: believe it. That's kind of what language is. So it's
Speaker 2: a common knowledge generator when it is something is blurted out.
Speaker 2: What got me interested in this whole topic is actually
Speaker 2: almost the converse cases in which we try to avoid
Speaker 2: common knowledge when we don't say something in so many words,
Speaker 2: but we put our meaning between the lines. We count
Speaker 2: on our reader to connect the dots. We use euphemism
Speaker 2: or innuendo or hinting or beating around the bush or
Speaker 2: hilly shallowing, which is a lot of language. That's one
Speaker 2: of the reasons it took so long to get computers
Speaker 2: to understand language. If you simply parse who did what
Speaker 2: to whom based on the subject of the verb and
Speaker 2: the object, you're really not going to understand what people
Speaker 2: actually meant, such as if you could pass a salt,
Speaker 2: that would be awesome. Okay, now think about that. I mean,
Speaker 2: that doesn't make it much sense. It would literally be awesome,
Speaker 2: And you know, it's not like you're just pondering possible worlds.
Speaker 2: That's not the meaning. Everyone knows what the meaning is.
Speaker 2: It's give me the salt, and a lot of languages
Speaker 2: like that, and linguists have long known it. But the
Speaker 2: question is why what do we try to accomplish when
Speaker 2: we avoid blurting something what we want out? In so
Speaker 2: many words, what I suggest is that the we're avoiding
Speaker 2: common knowledge. That is, each one knows what the other
Speaker 2: one is doing, but you may not know that the
Speaker 2: other one knows that you know that they know, and
Speaker 2: that allows you to preserve a certain relationship, relationships being
Speaker 2: coordination problems, as we mentioned at the top of the conversation,
Speaker 2: a relationship like being friends, being lovers, being a supervisor
Speaker 2: in supervisory, being transaction partners. Those are all matters of
Speaker 2: common knowledge. We're friends not because we signed a contract,
Speaker 2: but because each one knows that the other one knows
Speaker 2: that there we're friends, and that can be threatened by
Speaker 2: certain things that could become a common knowledge that contradict
Speaker 2: the basis of the friendship, like a sexual proposition. So
Speaker 2: why do people say things like I want to come
Speaker 2: up for Netflix and show, or you want to come
Speaker 2: up for coffee when you know, though you know, let's
Speaker 2: say it's a man saying it to a woman. You know,
Speaker 2: she wasn't born yesterday. She's a grown up, she knows
Speaker 2: what it means. But it's still way better than Hey,
Speaker 2: you want to come up and have sex, which would
Speaker 2: be you know, both parties. You are pretty uncomfortable, even
Speaker 2: though would you like to come up for coffee? Doesn't
Speaker 2: make them uncomfortable? How come that was the problem that
Speaker 2: I took up in a previous book, The Stuff of Thought.
Speaker 2: Language is a Window into human nature, which had a
Speaker 2: chapter called games People play on language as a window
Speaker 2: into social relationships and in trying to figure out why
Speaker 2: we don't just blurt out what we mean. Other examples
Speaker 2: being say a failed bribe. Let's see you trying to
Speaker 2: jump the queue in a restaurant and you slip the
Speaker 2: major DA twenty dollars bill and say, I just wondering
Speaker 2: if you might have a cancelation, or this is an
Speaker 2: important night from you. Is there any way to shorten
Speaker 2: my weight? Why don't people just say if I give
Speaker 2: you twenty dollars, will you see me? Right? Away or fundraising.
Speaker 2: I've seen this a lot at Harvard. I'm sure you've
Speaker 2: seen a similar thing where the dean will say to
Speaker 2: the rich people in the audience, we're counting on you
Speaker 2: to show leadership, to be a friend to the university
Speaker 2: instead of the reason we're all here is you're going
Speaker 2: to open your checkbook and write, you know, a check
Speaker 2: for five million dollars. That's another case where people don't
Speaker 2: say what they mean. Why not? And here's the answer
Speaker 2: that got me interested in common knowledge. And I've done
Speaker 2: studies to back this up that if it's do you
Speaker 2: want to come up for coffee? Well, you know, she
Speaker 2: knows what he means, and you know obviously he knows
Speaker 2: what he means. But does she know that he knows
Speaker 2: that she knows? With an innuendo like would you like
Speaker 2: to come up for coffee, she could think, well, maybe
Speaker 2: he thinks I'm naive, and if I said no, maybe
Speaker 2: he thinks, you know, caffeine would keep me up. Even
Speaker 2: though she knows that she's turned down a sexual overture,
Speaker 2: he knows it as well, but he could not know
Speaker 2: why because she knows that he knows. And likewise he
Speaker 2: could think, well, you know, maybe she thinks I'm dead,
Speaker 2: Maybe she thinks that I think that she's just turned
Speaker 2: down coffee. Uh. They can maintain their platonic friendship with
Speaker 2: the common knowledge that it's just about companionship. Whereas he
Speaker 2: said you want to come up for half sex and
Speaker 2: she said no, they can never be platonic friends in
Speaker 2: the same way. Again, the intuition is it's out there,
Speaker 2: you can't take it back, And I suggest that technically
Speaker 2: what's happening is that the blurted out speech generates common knowledge.
Speaker 2: Common knowledge is the basis of our relationships. Their coordination, games,
Speaker 2: euphemism and innuendo get a message across without generating common knowledge,
Speaker 2: and that's why we fall back on it so often.
Speaker 1: Okay, so that's how we sometimes try to mask common knowledge.
Speaker 1: Tell us about how common knowledge is useful in society,
Speaker 1: society wide, let's say, with public demonstrations and politics and economics.
Speaker 2: Yeah, a lot of our large scale coordination, not just
Speaker 2: two friends or Roande going for coffee or agreeing to
Speaker 2: be platonic friends, but large scale things like everyone recognizing money,
Speaker 2: Like why do I accept a green piece of paper
Speaker 2: in exchange for something of value? Well, because I know
Speaker 2: that other people will accept it and give me something
Speaker 2: of value. Why would they do that, Well, they know
Speaker 2: that still other people would accept it. So the value
Speaker 2: of currency depends on common knowledge. Everyone knows it's worth something,
Speaker 2: and that's what makes it worth something. The fact that
Speaker 2: everyone knows that everyone knows it. A lot of power
Speaker 2: depends on common knowledge. There are laws, there's courts, there's
Speaker 2: a police force, there's a jail. But most of the
Speaker 2: time people just follow the law, even though big brothers
Speaker 2: watching them twenty four to seven. However, these things can change.
Speaker 2: It's not easy to change them when the basis of
Speaker 2: power or money is just common knowledge, because everyone has
Speaker 2: an interest in keeping up the common assumption. But sometimes
Speaker 2: it can unravel. In the case of power, if there
Speaker 2: is a public protest, everyone shows up at a public
Speaker 2: square at the same time, the same place, everyone sees
Speaker 2: everyone else there. Previously, maybe that everyone was resentful of
Speaker 2: the system, thought it was inefficient and oppressive. They may
Speaker 2: even have suspected that everyone else had the same feeling,
Speaker 2: but they didn't know that other people knew that. They
Speaker 2: knew they couldn't coordinate by all rising at the same time,
Speaker 2: and so the regime could keep them in their place
Speaker 2: by preventing common knowledge. And that's why dictators don't allow
Speaker 2: freedom of assembly, freedom of the press, freedom of speech,
Speaker 2: precisely because they're afraid that people coordinating which they could
Speaker 2: only do with common knowledge, could acting together overpower a regime. Likewise,
Speaker 2: in the case of going back to money again, if
Speaker 2: the value of money depends on common knowledge, then when
Speaker 2: the common knowledge is threatened, the value of money can disappear.
Speaker 2: And that's what happens when you get hyperinflation, people taking
Speaker 2: home their wages in a wheelbarrow because no one will
Speaker 2: accept it anymore, or a bank run where people withdraw
Speaker 2: their savings, not necessarily because they think that there's anything
Speaker 2: wrong with a bank, but as long as there's a
Speaker 2: rumor that other people think that there's a problem with
Speaker 2: the bank, and they're withdrawing their money out of fear
Speaker 2: that still other people will withdraw their money, it suddenly
Speaker 2: becomes rational to withdraw your money while the bank still
Speaker 2: has money to withdraw. And that can cause a bank
Speaker 2: to fail, that can cause the whole economy to fail.
Speaker 2: That's what happened in nineteen twenty nine. And so when
Speaker 2: Roosevelt said the only thing we have to fear is
Speaker 2: fear itself. He was stating a theorem of common knowledge
Speaker 2: that was quite literally true, that what people had to
Speaker 2: fear was fear itself, and the fear of fear, the
Speaker 2: recursive fear, the common knowledge, could actually change the value
Speaker 2: of those financial institutions.
Speaker 1: So here's something I wanted to dig in with you
Speaker 1: about after reading your book. How do we think about
Speaker 1: false common knowledge? By which I mean, let's imagine that
Speaker 1: you and I engage in a public protest and we
Speaker 1: look around and we see a thousand people around us.
Speaker 1: We say, look, everybody clear feels this way, but we're
Speaker 1: not aware of that across town there's a larger protest
Speaker 1: with ten thousand people in it, and we have the
Speaker 1: impression that everyone feels the same way we do about something.
Speaker 2: I mean that technically be common belief rather than common knowledge,
Speaker 2: But different pools of people can have different common beliefs,
Speaker 2: and there can also be common misconceptions where prior to
Speaker 2: the protest, there are cases where people think that everyone
Speaker 2: else believes something. In fact, everyone could believe that everyone
Speaker 2: else believes someone something and no one actually believes it,
Speaker 2: sometimes called a pluralistic ignorance. Or a spiral of silence.
Speaker 1: What's an example of that.
Speaker 2: A classic case study of pluralistic ignorance in social psychology
Speaker 2: was when some psychologists interviewed the guys in the fraternity.
Speaker 2: They found that every one of them thought that it
Speaker 2: was really stupid to drink so much that you pass out,
Speaker 2: but everyone thought that all the other frat bros thought
Speaker 2: it was cool. No one actually thought it was cool,
Speaker 2: but that all the others thought it was cool. And
Speaker 2: there are probably a lot of cases like that. I mean,
Speaker 2: an extreme case would be The Emperor's New Clothes, where
Speaker 2: everyone thought that everyone else thought that who were seeing clothes,
Speaker 2: no one actually saw clothes, And it took the little
Speaker 2: boy blurting it out generating common knowledge, for the common
Speaker 2: misconception to flip into common knowledge. The Emperor's New Clothes
Speaker 2: is a story about common knowledge. The boy wasn't telling
Speaker 2: anyone anything they didn't already know, but it was changing
Speaker 2: the state of their knowledge because now everyone knew that
Speaker 2: everyone else knew, and that changed their relationship with the
Speaker 2: Emperor from a deference to scorn and ridicule.
Speaker 1: I do worry a little bit, though, about people assuming
Speaker 1: politically common knowledge and saying, Hey, if I just make
Speaker 1: some innuendo, everyone will understand what I mean by this,
Speaker 1: because that often doesn't work, especially now.
Speaker 2: Well, the thing about innuendo is that it has to
Speaker 2: be calibrated so that it is recognized by a kind
Speaker 2: of willing recipient, but can be denied by an unwilling recipient.
Speaker 2: So it has to be calibrated in that zone, and
Speaker 2: there can be errors in either direction. Where there's an
Speaker 2: episode of Seinfeld where George Costanza is invited up for
Speaker 2: coffee and says no because he's got to get to
Speaker 2: work early the next morning, and then as he's walking out,
Speaker 2: he says, oh, my god, coffee doesn't mean coffee. Coffee
Speaker 2: in sex. So there's the Costanza problem that it could
Speaker 2: be so subtle that it goes over the head, or
Speaker 2: there could be conversely, it's so blatant that the the
Speaker 2: unwilling hearer calls you on it again. You know, all
Speaker 2: of these things, by the way, are worked out in fiction,
Speaker 2: in comedies, comedies of manners, situation comedies. They kind of
Speaker 2: allow us to exercise our facility for recursive mentalizing, that is,
Speaker 2: getting inside the head of other people, getting inside the
Speaker 2: head of other people and so they're often worked out
Speaker 2: that so often were drives fictional plots. But the opposite
Speaker 2: is when when Harry met Sally, and Harry, you know,
Speaker 2: early on, is kind of complimenting Sally and they just
Speaker 2: met kind of a little too insistently, and then she
Speaker 2: blows the listle. She says, you're coming on to me,
Speaker 2: which leads to a wonderful discussion of common knowledge. I mean,
Speaker 2: not not in those words where he says, okay, let's
Speaker 2: say I was coming on to you. What are we
Speaker 2: going to do? I take it back? Okay, I take
Speaker 2: it back, and she says, you can't take it back.
Speaker 2: He says, what do you mean you can't take it back?
Speaker 2: You know, what are we going to do? Call the
Speaker 2: cop and she says, it's out there. It's too late,
Speaker 2: So it's out there. That is a metaphor for common knowledge.
Speaker 2: That is something that's out there, is something that you
Speaker 2: see other people see, you see them see it. And
Speaker 2: direct speech or even in this case, indirect speech that
Speaker 2: was not indirect enough. It kind of exceeded that. The
Speaker 2: cutoff is out there, and when it's out there, it
Speaker 2: changes the nature of the relationship. They were no longer
Speaker 2: just near strangers, platonic friends. He had turned it into
Speaker 2: a sexual relationship, which you rebuffed.
Speaker 1: Great, So I want to return for just a second
Speaker 1: to literature, which you mentioned fictions, because I made the
Speaker 1: argument on this podcast little while ago that I'm not
Speaker 1: so worried about AI completely taking the job of writers.
Speaker 1: And I listened five different reasons, but one of them
Speaker 1: had to do with the fact that we could all
Speaker 1: generate totally bespoke literature, just like Kings of Yesteryear would do.
Speaker 1: But we lose something there, which is that a big
Speaker 1: part of literature is the social glue, the fact that
Speaker 1: everyone else has read the same story. I don't want
Speaker 1: my Game of Thrones to have a different outcome than
Speaker 1: your Game of Thrones. So my question to you is,
Speaker 1: what is the reason we desire common knowledge so much?
Speaker 2: I think it's a great example, and people may not
Speaker 2: remember that back in the nineties, when the internet first
Speaker 2: became a thing, there was the idea that you could
Speaker 2: dial in whatever ending to a story you wanted. That
Speaker 2: fiction would be, movies would be the same. Everyone could
Speaker 2: watch that movie. Maybe let's they didn't take off. And
Speaker 2: I think it's the reason that you identified, namely part
Speaker 2: of the experience of art is that it's common knowledge.
Speaker 2: You know about something at the same time you know
Speaker 2: that everyone else knows about it, and that's what gives
Speaker 2: you something in common that can reinforce a social relationship.
Speaker 2: With friendship, a movie with friends, you talk about it
Speaker 2: with friends, and the common experience is one of those
Speaker 2: things that kind of go makes friends friends. They go
Speaker 2: through things together, they share common interests. The basis, the
Speaker 2: common knowledge, that's the tacit basis of friendship is that
Speaker 2: we're kind of there's a kind of a mind mild,
Speaker 2: even a you know, a body meld, where that we
Speaker 2: are in physical proximity, We hug, we shake hands, all
Speaker 2: the more intense and romantic relationship.
Speaker 1: Okay, So I want to return and dig in just
Speaker 1: a little on this point because I'm fascinated by this
Speaker 1: about false common knowledge what I'm calling that or a
Speaker 1: misconception about it. So, for example, recently, Charlie Kirk was
Speaker 1: assassinated in broad daylight, and if you look on X
Speaker 1: and if you look on blue Sky, you find very
Speaker 1: different stories about that. And presumably the people who are
Speaker 1: tweeting or blue skying are thinking, hey, this is great.
Speaker 1: We have shared common knowledge. But you in fact have
Speaker 1: two groups of people. I'm exaggerating a little bit the difference,
Speaker 1: but you have different groups that have beliefs that they
Speaker 1: believe are shared by everybody. Just one second example. This
Speaker 1: My grandmother I remember many years ago in Florida said
Speaker 1: I can't believe that so and so just one governor,
Speaker 1: because I don't know anybody that voted for him. And
Speaker 1: it was true, of course she didn't know anybody, but
Speaker 1: it doesn't mean that the majority of the state didn't
Speaker 1: vote for him.
Speaker 2: Nonetheless, Yeah, I mean common knowledge, or more accurately, in
Speaker 2: a lot of these cases, is common belief, That is,
Speaker 2: you believe something, you believe that other people believe that
Speaker 2: you believe it, and so on. Is relative to a network,
Speaker 2: a community which can be disconnected from another network, and
Speaker 2: the common knowledge is often generated since none of us
Speaker 2: experience everything firsthand. In fact, on for politics, we experience
Speaker 2: almost nothing firsthand, and we read about it, we hear
Speaker 2: about it. If the sources are disjoint, then the pools
Speaker 2: of common knowledge within each of these networks could be disjoined.
Speaker 2: And that happens partly from social media, as even feeds
Speaker 2: within a platform, but even more so when they're different
Speaker 2: platforms like X versus Blue Sky, or in the case
Speaker 2: of cable news, do you watch Fox News or do
Speaker 2: you watch CNN or do you watch MSNBC. So one
Speaker 2: of the users I take up in the book, and
Speaker 2: this intersects with my interest in academic freedom and freedom
Speaker 2: of speech in another part of my life where I
Speaker 2: co founded and I'm the co president of the Council
Speaker 2: and Academic Freedom at Harvard. Why is free speech so
Speaker 2: important and all the more so in a country? Why
Speaker 2: is freedom of speech enshrined in the First Amendment to
Speaker 2: the American Constitution, Freedom of the press, freedom of assembly.
Speaker 2: So what is it about speech that can be so
Speaker 2: threatening to a dictator? You might think, Well, the dictator
Speaker 2: would be tend to let people bitch and moan all
Speaker 2: they want. He's what with the guns, And as Mao said,
Speaker 2: power comes out of the barrel of a gun. So
Speaker 2: why should a public protest or a critical editorial be
Speaker 2: so threatening to a dictator? Well, the reason is, as
Speaker 2: Gandhi said in the eponymous movie, he says to a
Speaker 2: British officer in the end, you will leave because there's
Speaker 2: simply no way that one hundred thousand Englishmen can control
Speaker 2: three hundred and fifteen million Indians if the Indians refuse
Speaker 2: to cooperate. So that's just a truth about numbers then,
Speaker 2: But it raises the question, how do you get three
Speaker 2: hundred and fifteen million people cooperating or in this case coordinating. Well,
Speaker 2: some public event demonstration where you're protesting, you can see
Speaker 2: everyone else protesting, and everyone can see everyone else. You know,
Speaker 2: the time is now a prominent public uh declaration you know,
Speaker 2: Jacques or an article. Everyone knows now that it's public
Speaker 2: that everyone hates the regime and people can, you know,
Speaker 2: either storm the palace or just refuse to work or
Speaker 2: to cooperate. And so dictators don't want that to happen.
Speaker 2: They want to prevent the generation of common knowledge, which
Speaker 2: is why police states control both public assembly and public media.
Speaker 2: I give a joke. I recount a joke from the
Speaker 2: era of the Soviet Union in which a man is
Speaker 2: handing out leaflets in Red Square and of course they're
Speaker 2: sure enough the KGB arrested. They take them back to headquarters,
Speaker 2: only to discover that these leaflets are blank sheets of paper,
Speaker 2: and they think, what is the meaning of this? And
Speaker 2: he says, what's there to say, it's so obvious. So
Speaker 2: that's a joke about common knowledge. Namely, he was being
Speaker 2: subversive because by the very act just handing out leaflets
Speaker 2: didn't matter what they said. That now everyone who accepted
Speaker 2: the leaflets accepting seeing everyone else except the belief that
Speaker 2: they all knew that there was something to protest, and
Speaker 2: they didn't have to be told what it was because
Speaker 2: they knew privately what it was. The act of communication
Speaker 2: was that giving it out in a public square made
Speaker 2: the private knowledge common, and that was threatening to the regime,
Speaker 2: which is why, in a case of life imitating a joke,
Speaker 2: Putin's regime has arrested people for carrying blank science.
Speaker 1: I'm sorry to return to this point, but if you
Speaker 1: stood on a street corner and said I'm protesting, and
Speaker 1: you handed out blank sheets of paper, the lefties would
Speaker 1: think one thing from the blank sheet, and the right's
Speaker 1: would think another thing. And so in an ideal sitution,
Speaker 1: I mean, we look at the Soviet regime as a failure,
Speaker 1: and so we say, okay, it was obvious what he
Speaker 1: meant by that. But I'm interested in the fact that
Speaker 1: we each have very different internal models. Let's say, with
Speaker 1: politics and so the transmission of common knowledge isn't so
Speaker 1: easy in a sense.
Speaker 2: Well, yes, I mean it depends on a conspicuous public
Speaker 2: signal and in general from a trusted source and who
Speaker 2: trusts who can vary between interconnected but disjoint networks of people.
Speaker 2: But it's not, you know, it's not the case that
Speaker 2: everyone goes that own way. Otherwise we wouldn't have society,
Speaker 2: we wouldn't have science, we wouldn't have markets, we wouldn't
Speaker 2: have currency.
Speaker 1: But we do have parties. We do have two different
Speaker 1: parties that increasingly disagree more and more we do.
Speaker 2: Yes, I mean that, As I said, there can be
Speaker 2: the common belief within semi disconnected networks, within each of
Speaker 2: which you have common belief, but not necessarily in the
Speaker 2: the entire group. The general phenomena are that common knowledge
Speaker 2: is generated by public signals that people see when they
Speaker 2: know that everyone else sees sees themselves seeing it. And
Speaker 2: again that can be relative to pop the population and
Speaker 2: the connected network that sees each other seeing something at
Speaker 2: the same time.
Speaker 1: So tell us about cancel culture and also why cancel
Speaker 1: culture is more possible in a world where people can
Speaker 1: hide behind keyboards.
Speaker 2: Yes, I have a chapter in the book called the
Speaker 2: Canceling Instinct, and it does touch on my interest in
Speaker 2: academic freedom, but the point of the chapter isn't so
Speaker 2: much to make the case for academic freedom, though I
Speaker 2: do reprise that, but as a psychologist, to ask, why
Speaker 2: is there an urge to censor, to cancel, to punish
Speaker 2: people for their opinions. Now, of course that's been true
Speaker 2: for all of human history, or heretics have been burned
Speaker 2: at the stake or crucified. But you think that in
Speaker 2: universities of all places, for the arena where we ought
Speaker 2: to be, not treat beliefs as sinful. May be mistaken,
Speaker 2: maybe illogical, but then you point it out, why do
Speaker 2: you try to destroy the person who's ventured that opinion.
Speaker 2: That's the phenomenon of cancel culture, and I suggest it's
Speaker 2: because a combination of two psychological phenomena. One of them
Speaker 2: is that even though the whole basis of science and
Speaker 2: scholarship is there is a truth, we have means to
Speaker 2: try to approach it. We may be mistaken, but we're
Speaker 2: not bad people because we're mistaken. That you believe things
Speaker 2: to the extent that there's good evidence for, good arguments
Speaker 2: for it, that whole complex of beliefs is kind of
Speaker 2: weird in human history. And the more common attitude is
Speaker 2: for most people most of the time, is your beliefs
Speaker 2: are a reflection of who you are, whether in particular
Speaker 2: what tribe you belong to, and whether you're a good person,
Speaker 2: who usually means upholding the sacred beliefs of your tribe.
Speaker 2: Now that is poison for science and for scholarship and
Speaker 2: for academia. But it is the way that people think
Speaker 2: that the beliefs I mean putting aside beliefs about here
Speaker 2: and now, I mean there are you know, people don't hallucinate.
Speaker 2: They know, you know there's food in the fridge. There
Speaker 2: isn't food in the fridge. But when it comes to
Speaker 2: more bigger questions, where did humans come from? Why is
Speaker 2: their disease? Why are their revolutions? Why is their wealth
Speaker 2: and inequality? Things that we academics tend to think can
Speaker 2: be answered by the methods of science and scholarship. But
Speaker 2: most people is what you believe signals what tribe, what
Speaker 2: coalition you belong to, And you're bad if you have
Speaker 2: the wrong belief So if you have that kind of
Speaker 2: built in flaw in human belief, then there can be
Speaker 2: norms as to what you believe in what you don't believe.
Speaker 2: And norms are matters of common knowledge. They exist because
Speaker 2: people believe they exist. They can be threatened if people
Speaker 2: flout them and get away with it. So and we
Speaker 2: have everyday social norms. You don't go around naked, you
Speaker 2: don't make you pass gas in public, you don't tell
Speaker 2: ethnic jokes anymore, you don't insult people's appearance to their face.
Speaker 2: All these norms are held up just because it isn't done,
Speaker 2: and everyone knows that it isn't done. Conversely, if it
Speaker 2: is done, the norm can unravel. So people often feel
Speaker 2: the need to prop up norms by if noting when
Speaker 2: they're flouted in public and then punishing the violator in public.
Speaker 2: And the punishment has to be public for it to
Speaker 2: prop up the norm, which is why we used to
Speaker 2: have public hangings and pillories and stocks and crucifixions. Only
Speaker 2: if you have everyone seeing that the person is punished,
Speaker 2: could the norm survive well. I think we now have
Speaker 2: an equivalent, often an electronic equivalent, in social media, where
Speaker 2: if someone does flow a norm, that is, they express
Speaker 2: an opinion that goes against what you take to be
Speaker 2: the moral convictions of your tribe. People feel the urge
Speaker 2: to punish it in public, and that's really easy to
Speaker 2: do on social.
Speaker 1: Media and the anonymity of being behind the keyboard. I think,
Speaker 1: you know, it's just like the trolley dilemma, where if
Speaker 1: you have to push the person with your hands, it's different.
Speaker 1: You activate these motional networks and you're less likely to
Speaker 1: do that. But if you have to pull the lever
Speaker 1: so that only one person gets killed instead of five people,
Speaker 1: then most people are perfectly willing to do that at
Speaker 1: a distance. And it strikes me it's the same thing
Speaker 1: with the anonymity.
Speaker 2: Well, that's right. And it also and this does relate
Speaker 2: to another common knowledge phenomenon, that is that our social relationships.
Speaker 2: Are we friends? Are we lovers? Are we boss and subordinate?
Speaker 2: Are we neighbors, members of a civil society? A lot
Speaker 2: of these are reinforced by common knowledge generators. Eye contact, handshakes, laughter, blushing,
Speaker 2: eye contact, things that can't be denied. That is, you
Speaker 2: look someone in the eye, you're looking at the part
Speaker 2: of them that's looking at the part of you that's
Speaker 2: looking at the part of them that's looking at the
Speaker 2: part of you, ad infinitum. So it's an eye contact
Speaker 2: is a common knowledge generator, and the common knowledge that
Speaker 2: these signals generate tend to be things like, well, we're
Speaker 2: all acting like we're members of a community. So indeed,
Speaker 2: when those signals are present because you're face to face,
Speaker 2: then that can restore the norms of how you deal
Speaker 2: with a person in a peer group, namely, you don't
Speaker 2: insult them to your face. Without those common knowledge generators,
Speaker 2: such as in the anonymity of a keyboard, then you
Speaker 2: can insult people, you can denigrate them, you can try
Speaker 2: to destroy the reputations in a way that would be
Speaker 2: kind of unthinkable in a face to face situation.
Speaker 1: There's one piece I want to return to about cancel culture,
Speaker 1: which is why everybody jumps on the bandwagon. You had
Speaker 1: a section in your book about moral condemnation and why
Speaker 1: it's better to join the bullies than to take the
Speaker 1: risk of being bullied.
Speaker 2: Yeah, yeah, give us a sense exactly. I mean, it's
Speaker 2: a kind of a playground dynamic that many of us
Speaker 2: remember sometimes with shame, when we may have joined the
Speaker 2: bullying mob and out of fear of becoming the kid
Speaker 2: that everyone picks on and there is there's an equivalent
Speaker 2: in academias. I had to say where I mean, it
Speaker 2: has no place because we're all in it together trying
Speaker 2: to find the truth. But you get the instant petition
Speaker 2: with six hundred signatures, which can usually gin up on
Speaker 2: social media. There are enough grad students in the country
Speaker 2: that you can get get this is to sign some
Speaker 2: condemnatory petition. But I think it is some of the
Speaker 2: same dynamic, and there is a dynamics. Sorry to keep
Speaker 2: relating things to common knowledge, because it is the theme
Speaker 2: of the book, the theme of our conversation, but I
Speaker 2: do think that it governs many human interactions. There's a
Speaker 2: theory from a former post doc online Peter to Sholey
Speaker 2: and his former advisor Rob Kurzband that we know no
Speaker 2: one is an island. We really want to be part
Speaker 2: of some group, some posse, some band of brothers, because
Speaker 2: you know we're sitting ducks. If we're isolated, how do
Speaker 2: you know which group to join? You don't want to
Speaker 2: be on the losing side. If you can find some
Speaker 2: sin that someone has committed and you all jointly recognize
Speaker 2: that they are a sinner, they've broken some norm some law,
Speaker 2: you gang up on them. That's a and it's common
Speaker 2: knowledge as you know that the other people recognize that
Speaker 2: same violation. It is a basis for forming a coalition,
Speaker 2: and people often will band together and to single out
Speaker 2: some victim as and there's something that feels right about
Speaker 2: being in that band, and it is the basis that
Speaker 2: the coalitions could form and the target suffers their kind
Speaker 2: of collateral damage. Probably the episode from fiction that kind
Speaker 2: of draws that out of the most is the famous
Speaker 2: story by Shirley Jackson called The Lottery, came out in
Speaker 2: the late forties, often assigned in high school and debated
Speaker 2: ever since, where the town folk of a Bucolic village
Speaker 2: every year choose someone by lottery and stone to death
Speaker 2: as a person, suggesting that there is some kind of
Speaker 2: human urge to simply gang up on a victim and
Speaker 2: they in this case. What makes the story so chilling
Speaker 2: and so kind of absurd is the victim didn't actually
Speaker 2: do something other than being the loser in the lottery.
Speaker 2: But what it kind of played out, what continues to
Speaker 2: make it fascinating is this dynamic of being part of
Speaker 2: a mob united in its victimization of a victim.
Speaker 1: Yeah, so it doesn't only have to do with the violation,
Speaker 1: It has to do with the social bonding that results. Okay, great,
Speaker 1: what else should everybody know about common knowledge?
Speaker 2: Yes? Well, one of my favorite chapters, the one that
Speaker 2: I had one of the most fun writing, was the
Speaker 2: one on body language social signals laughing, crying, blushing, staring,
Speaker 2: glaring on signals that I think we fall because they
Speaker 2: were common knowledge generators. So in case, you know, why
Speaker 2: do we blush? The mark twains and men is the
Speaker 2: only animal that blushes or needs to and he was
Speaker 2: he is right that men are. You know, humanity is
Speaker 2: the only animal that plushes. There are other things that
Speaker 2: also that make humans unique. We're the only species that
Speaker 2: that weeps. We're the only species that laughs. There's a
Speaker 2: kind of precursor in chimpanzees in a kind of panting
Speaker 2: that a companies play fighting. But you know, it's not
Speaker 2: like are exactly the same as our laughter. We are.
Speaker 2: Eye contact is really important to humans, and that's probably
Speaker 2: why we evolved a white sclera, the whites of our
Speaker 2: eyes that other primates don't have. Why we have elongated
Speaker 2: eyes so that our position of our eyes can easily
Speaker 2: be discerned. So all of these I suggest are effective
Speaker 2: because they when you express them, the perceiver knows that
Speaker 2: you know that you're expressing them. So in the case
Speaker 2: of blushing, you feel the heat of your cheeks from
Speaker 2: the inside at the same time that you know that
Speaker 2: other people can see them redden from the outside and
Speaker 2: they know that you're feeling it. Because what makes blushing
Speaker 2: so painful is knowing that other people know that you're blushing,
Speaker 2: as when people say you're blushing, which makes people blush
Speaker 2: all the more and can even make them blush if
Speaker 2: they're not blushing, you know, or or tearing up weeping.
Speaker 2: You're seeing the world through the kind of the scrim
Speaker 2: of your own tears, and other people can see the
Speaker 2: glisten or the trickle of your tears. So these are
Speaker 2: cases where I think you're establishing something about your relationship
Speaker 2: with the person in a involuntary, unfakable, and undeniable way.
Speaker 2: In the case of blushing, it's I know that I've
Speaker 2: screwed up by the norms that you hold, and so
Speaker 2: even though I've screwed up, better that I know that
Speaker 2: I've screwed up than that I just blow off your
Speaker 2: norms as if I was some kind of loose cannon
Speaker 2: or weirdo or psychopath. In the case of crying, it's
Speaker 2: I acknowledge, defeat, surrender, helplessness. I'm not going to fight back.
Speaker 2: It's going to be bodily equivalent of raising a white
Speaker 2: flag or throwing in the towel in a boxing match. Anyway,
Speaker 2: I talk about each one of these displays and why
Speaker 2: I think they evolved as a common knowledge generator in
Speaker 2: order to ratify a certain kind of social relationship.
Speaker 1: Excellent, Yeah, I love that chapter. Okay, any closing thoughts
Speaker 1: about common knowledge?
Speaker 2: Yeah, just is. I think it's a missing piece of
Speaker 2: the puzzle of a lot of human life that a
Speaker 2: lot of would seem to be arbitrary. Rituals, conventions, hypocrisy
Speaker 2: do have a hidden rationale in terms of either generating
Speaker 2: or denying common knowledge, including all of the ways in
Speaker 2: which we are systematically hypocritical, genteel, polite, dainty. We don't
Speaker 2: blurt out things that all of us know privately but
Speaker 2: we don't know commonly, and there's a reason for that.
Speaker 2: It's necessary to preserve and retain certain social relationships on
Speaker 2: which social life depends, and that, as certain comedies point
Speaker 2: out where they envision a world in which someone or
Speaker 2: everyone is forced to be honest. It quickly becomes a dystopia,
Speaker 2: and the characters are glad to go back to a
Speaker 2: state in which you don't say everything that you need.
Speaker 1: That was my interview with Stephen Pinker. His new book
Speaker 1: is called When Everyone Knows That Everyone Knows, Common Knowledge
Speaker 1: and the Mysteries of Money, Power, and Everyday Life. The
Speaker 1: book tackles many mysteries of life and psychology centered on
Speaker 1: this question of how humans manage to coordinate on scales
Speaker 1: that range from two drivers in a game of chicken
Speaker 1: to millions of people in a nation. A lot of
Speaker 1: the answers lie in this recursive loop of awareness that
Speaker 1: we call common knowledge. Pinker shows us in the book
Speaker 1: that common knowledge is at least some of the engine
Speaker 1: behind laughter, applause, etiquette, trust, diplomacy, and financial markets. And
Speaker 1: common knowledge is the difference between a thousand private doubts
Speaker 1: and a public turning point in history. Private knowledge lives
Speaker 1: in our skulls, but common knowledge spills into the shared
Speaker 1: spaces between us, and it's what transforms isolated individuals into
Speaker 1: a civilization. In our daily lives, we hardly notice it,
Speaker 1: but every time that we have on the correct side
Speaker 1: of the road, or laugh at the same moment in
Speaker 1: the theater, or rise to our feet in a standing ovation.
Speaker 1: We're participating in a recursive dance of shared awareness. The
Speaker 1: thing that's so striking is how invisible it generally.
Speaker 2: Is to us.
Speaker 1: But common knowledge is the thread that binds strangers into
Speaker 1: this mad, wild, beautiful collective that we call society. Go
Speaker 1: to eagleman dot com slash podcast for more information and
Speaker 1: find further reading. Join the weekly discussions on my substack
Speaker 1: and check out Subscribe to Inner Cosmos on YouTube for
Speaker 1: videos of each episode and to leave comments until next time.
Speaker 1: I'm David Eagleman, and this is Inner Cosmos.