Rational Ritual

Coordination and Common Knowledge

When you want to do something with other people, you may face “coordination problems.” You want to participate only if you know others are participating as well. Communicating with others addresses your immediate decision, but just sending or receiving messages isn’t enough. You also need to know what others know. You need “common knowledge.”

Coordination problems differ from the “free rider problem.” In that situation, no one wants to join with others: Each person would rather be the free rider who takes advantage of others’ actions, like the person who rides the city bus without paying the fare. To solve free rider problems, you have to shift people’s motivations so they support the common good. However, all those who take part in an event don’t have to share the same motive. You might join a demonstration because you want to overturn the government, but your friend might only want to observe a big protest.

“Public Rituals”

To understand common knowledge, consider how societies create it. For one, public rituals such as “ceremonies, rallies and media events” are “social practices that generate common knowledge.” Public...