site banner
PaperclipPerfector  1yr ago (text post)   3383 thread views

Small-Scale Question Sunday for August 11, 2024

Do you have a dumb question that you're kind of embarrassed to ask in the main thread? Is there something you're just not sure about?

This is your opportunity to ask questions. No question too simple or too silly.

Culture war topics are accepted, and proposals for a better intro post are appreciated.

3
Top Bottom Old Controversial Comments
Jump in the discussion.

No email address required.

I'm very interested in the idea of common knowledge. It's been talked a lot about by the Scotts here and here

The crucial concept here is common knowledge. We call a fact “common knowledge” if, not only does everyone know it, but everyone knows everyone knows it, and everyone knows everyone knows everyone knows it, and so on.

I sort of understand this but I want to understand it better. Can someone explain this to me? Why is something not common knowledge if everyone knows that everyone knows it? What is the difference between that and the next level (everyone knows that everyone knows that everyone knows it)? I want to get a more intuitive grasp of that.

The concept often comes up in the context of dictatorships, so that's the context I'll use to illustrate it.

Alice, Bob and Carol live in the Soviet Union during Stalin's regime. Alice hates Stalin and wishes him dead. But Alice has never read a column or editorial which was even mildly critical of Stalin (Stalin controls Pravda), and also knows that everyone who criticises Stalin in any capacity immediately vanishes to the gulag, never to be heard from again. For fear of this happening to her, Alice never criticises Stalin in front of Bob and Carol. Unbeknownst to Alice, Bob and Carol also hate Stalin, but have performed exactly the same risk calculus and decided never to publicly criticise Stalin. Hence conversations between Alice, Bob and Carol consist of three people loudly, conspicuously praising Stalin and successfully deceiving the others that they sincerely admire Stalin and think he's the bee's knees - but all three of them hate him and erroneously believe that they're the only one of the three to think so.

There's a sophomoric theory of how dictatorships come to an end: "people admired Stalin, but then a critical mass of people turned against him and the public rose up to overthrow him". The toy example above illustrates why this theory is wrong: a critical mass of people hating the dictator is necessary but not sufficient to effect an overthrow of the dictatorship. It's perfectly possible for a simple or supermajority of the population to hate the dictator, but for the dictator to remain in power if enough of the people who hate him erroneously believe that their opinion is a minority or fringe opinion. It's not enough for Alice, Bob etc. to hate Stalin: Alice must also know that Bob hates Stalin, and Bob likewise - Stalin must be widely despised, and it must be common knowledge that Stalin is widely despised.

Alice, Bob and Carol live in the Soviet Union during Stalin's regime. Alice hates Stalin and wishes him dead. But Alice has never read a column or editorial which was even mildly critical of Stalin (Stalin controls Pravda), and also knows that everyone who criticises Stalin in any capacity immediately vanishes to the gulag, never to be heard from again. For fear of this happening to her, Alice never criticises Stalin in front of Bob and Carol. Unbeknownst to Alice, Bob and Carol also hate Stalin, but have performed exactly the same risk calculus and decided never to publicly criticise Stalin. Hence conversations between Alice, Bob and Carol consist of three people loudly, conspicuously praising Stalin and successfully deceiving the others that they sincerely admire Stalin and think he's the bee's knees - but all three of them hate him and erroneously believe that they're the only one of the three to think so.

This much makes sense to me, but beyond this it gets tough for me. This sounds like "everyone knows Stalin sucks, but everyone doesn't know that everyone knows Stalin sucks". But let's say everyone did know that everyone knows Stalin sucks. Why is that not common knowledge already? Why is it important that everyone knows that everyone knows that everyone knows that Stalin sucks?

To throw another explanation into the arena: Alice, Bob and Carol currently hate Stalin but each thinks they are alone, so they don't rebel. If Alice found a credible note saying "Bob hates Stalin. Carol hates Stalin." Then she has learned a little, but her options don't increase all that much.

  • She can't try to convince Bob to form a rebellion. Since Bob hasn't gotten a note, he will just assume Alice is an agent trying to catch Bob doing something bad. (Haven't dictatorial regimes employed snitches? Sounds familiar right?)
  • She can't really tell Bob: "I know you hate Stalin." Like before, Bob will assume she is an agent. After all, Bob thinks he's the only one opposing Stalin! (Don't governments deploy sting operations to catch detractors? Glowies etc.)
  • She could try to be honest and vulnerable with Bob and say "I hate Stalin." This is actually risky. I can't search for it now and probably couldn't find it - a blog post about how these scenarios, and expectations, affect friendships. Since the social norm is to report your friends who hate Stalin, then Alice's admission is like saying: "Report me." Bob can maybe reason that Alice expects to be safe telling her friend Bob this. Or in other words, Alice has accused Bob of hating Stalin. This would freak Bob the fuck out. I know I would freak out if one of my friends said they were into ISIS or some kind of terrorist group.

Anyways, the above bullet points are just Alice's thought process. In reality, Bob also got a note saying "Alice hates Stalin. Carol hates Stalin." And Carol also got a similar note. The problem, hopefully you see, is that the notes are secret.

What is this place?

This website is a place for people who want to move past shady thinking and test their ideas in a court of people who don't all share the same biases. Our goal is to optimize for light, not heat; this is a group effort, and all commentators are asked to do their part.

The weekly Culture War threads host the most controversial topics and are the most visible aspect of The Motte. However, many other topics are appropriate here. We encourage people to post anything related to science, politics, or philosophy; if in doubt, post!

Check out The Vault for an archive of old quality posts. You are encouraged to crosspost these elsewhere.


Why are you called The Motte?

A motte is a stone keep on a raised earthwork common in early medieval fortifications. More pertinently, it's an element in a rhetorical move called a "Motte-and-Bailey", originally identified by philosopher Nicholas Shackel. It describes the tendency in discourse for people to move from a controversial but high value claim to a defensible but less exciting one upon any resistance to the former. He likens this to the medieval fortification, where a desirable land (the bailey) is abandoned when in danger for the more easily defended motte. In Shackel's words, "The Motte represents the defensible but undesired propositions to which one retreats when hard pressed."

On The Motte, always attempt to remain inside your defensible territory, even if you are not being pressed.


New post guidelines

If you're posting something that isn't related to the culture war, we encourage you to post a thread for it. A submission statement is highly appreciated, but isn't necessary for text posts or links to largely-text posts such as blogs or news articles; if we're unsure of the value of your post, we might remove it until you add a submission statement. A submission statement is required for non-text sources (videos, podcasts, images).

Culture war posts go in the culture war thread; all links must either include a submission statement or significant commentary. Bare links without those will be removed.

If in doubt, please post it!


Rules


Recommended Posts And Communities

Recommended Realtime Chats