Mutual Knowledge
Updated 2026-08-13
INTRODUCTION
English translation pending.
CORE DEFINITION
Mutual knowledge exists when A knows X and B knows X, and each knows that the other knows, up to a finite number of levels. Common knowledge is the limiting case in which this recursion holds to unlimited depth. The core proposition is that coordination requires not only that each party knows something but that each party knows the others know it, because otherwise each must guess whether the others will act. The qualification is that the distinction matters only when the information itself is already shared.
SCAFFOLDING EFFECT
Reduce cognitive load
- Level check: ask how many levels of knowing the situation actually requires. - Public signal: create a shared announcement so that everyone knows the others received it. - Coordination design: verify the recursion rather than assuming shared information produces coordination.
Anchor fast decisions
Acting on shared information requires anticipating whether others will act on it too, and that anticipation requires knowing that they know. Without the recursion, each party is uncertain about the others' response and may rationally wait, so coordination fails even though everyone holds the same information. A public signal creates the recursion because each party observes the others receiving it.
MINIMUM ACTION
In progress 0/1Practice this model in one real situation:
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Source support: Explicit
- en.wikipedia.orghttps://en.wikipedia.org/wiki/Mutual_knowledgeverified
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