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Common Knowledge and Coordination
“Everyone knowing the time may not be enough; they may need to know that others know it too.”
01 / SUMMARY
In short
A fact is common knowledge when it is known, everyone knows that others know it, and so on. Public signals can support coordination by aligning expectations about expectations.
03 / SCENE
In the wild
A room-wide evacuation announcement coordinates better than identical private messages whose receipt nobody can confirm.
04 / LIMIT
The limit
Common knowledge is not popular information, consensus, or an infinite calculation people consciously perform.
FINAL NOTE
What remains
When action depends on others, communicate that the message arrived publicly and jointly.