AI Summary
5 min readCommon knowledge is not what you think it is
In the technical sense used by mathematicians and logicians, common knowledge does not mean something everyone knows. It means something everyone knows that everyone knows — and everyone knows that, and so on, to infinite depth. As Steven Pinker explains in this episode of Instant Genius, this seemingly subtle distinction has profound consequences for how societies coordinate, how norms form and collapse, and why people sometimes act in ways that seem irrational.
The emperor's clothes problem
The classic illustration is Hans Christian Andersen's tale of the Emperor's New Clothes. The little boy who blurts out that the emperor is naked does not tell anyone anything they did not already know — everyone could see the emperor was naked. But he changes their state of knowledge nonetheless. By shouting it within earshot of everyone, he makes it common knowledge. The crowd's relationship to the emperor shifts instantly from obsequious deference to ridicule and scorn.
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What you'll learn
- 1 (03:57) **Defining Common Knowledge** - Steven Pinker distinguishes the everyday term from the technical, logical definition used by mathematicians and economists.
- 2 (04:48) **The Emperor's New Clothes as a Case Study** - The classic fairy tale illustrates the shift from everyone knowing something to everyone knowing that everyone knows it.
- 3 (06:00) **Coordination and Social Relationships** - Pinker explains that social relationships are coordination games, analogous to a rendezvous.
- 4 (06:40) **Common Knowledge Within Groups** - The concept is relative to the specific culture or subculture in which it exists.
- 5 (08:58) **Social Norms and Politeness** - Norms are held up by common knowledge; they exist only as long as everyone knows that everyone else knows they exist.
- 6 (11:18) **The Logic of Public Outrage** - Outrage is a response to a perceived public affront that threatens a group's status or respect.
- 7 (14:28) **Morals and Norms** - Morals are often implemented as social norms, but this can be both beneficial and harmful.
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Guests on this episode
Show Notes
When we know a certain fact about the world or hold a certain belief how do we know that others also know this, how do we base our thoughts and actions on our knowledge of what we assume others know, and what impact does this have on the way that society as a whole functions?
In this episode, we’re joined by Steven Pinker, a professor of psychology at Harvard University, best-selling author and two-time Pulitzer Prize finalist, to talk about his latest book, When Everyone Knows That Everyone Knows – Common Knowledge and the Science of Harmony, Hypocrisy and Outrage.
He tells us about the effects common knowledge has on social norms and the ways in which we all act, the profound effects that the Internet and social media has had on the way that common knowledge is spread and consumed, and how deepening our understanding of the implications common knowledge has on our lives can help us all get along more harmoniously.
Take your curiosity further with a subscription to BBC Science Focus magazine. Every issue is packed with fascinating insights into the science behind everyday life, the latest breakthroughs and expert analysis, delivered straight to your door. Receive an extra £5 when you subscribe using the code SF5OFF, (minimum spend £20, see full terms and conditions on our website).
https://www.ourmediashop.com/bbc-science-focus-magazine-pod30
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