共有知識と共同知識について、ここに記述してください。

「世界でもっとも奇妙な数学パズル」：　IMPOSSIBLE

http://www.amazon.co.jp　で買ったもの。

共有知識（と共同知識）を題材にしたパズル

https://ja.wikipedia.org/wiki/%E5%85%B1%E6%9C%89%E7%9F%A5%E8%AD%98


共有知識: common knowledge　　http://plato.stanford.edu/entries/common-knowledge/

mutual knowledge を共同知識を訳しているが、適当ではなさそう。

mutual knowledge は individual knowledge の対語として現れる。

https://en.wikipedia.org/wiki/Mutual_knowledge_%28logic%29
{{{
Mutual knowledge is a fundamental concept about information
in game theory, (epistemic) logic and epistemology.

An event is mutual knowledge if all agents know that the event occurred [1]:73.

However, mutual knowledge by itself implies nothing about what agents know about other agents' knowledge: 
i.e. it is possible that an event is mutual knowledge but that each agent is unaware that
the other agents know it has occurred.[2]

Common knowledge is a related but stronger notion; any event that is common knowledge is also mutual knowledge.

The philosopher Stephen Schiffer, in his book Meaning, developed a notion he called "mutual knowledge" 
which functions quite similarly to David K. Lewis's "common knowledge".[3]
}}}

http://www.gametheory.net/dictionary/MutualKnowledge.html