Cyan comments on Teachable Rationality Skills - Less Wrong

52 Post author: Eliezer_Yudkowsky 27 May 2011 09:57PM

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Comment author: Cyan 30 May 2011 04:08:24PM *  0 points [-]

2 . Interpreting Aumann’s theorem to mean what Aumann said it means... That is a fine semantic error buried deep within the English interpretation, but it makes the entire theorem worthless.

That was way too densely packed for my sleep-deprived brain to parse. Would you be willing to write a post (possibly Discussion post) spelling this out less succinctly? It seems important to get this idea out into the LW-sphere given how much cred the agreement theorem has around here.

Comment author: PhilGoetz 30 May 2011 06:46:07PM 0 points [-]

It's not just densely packed - it makes no sense unless you read the paper first, and read some other things necessary to understand that paper. I'd like to write a post - but not right now.

Comment author: Will_Sawin 30 May 2011 06:56:31PM 0 points [-]

I know enough game theory to prove versions of Aumann's theorem, but I have not read the paper, and your point in (2) makes no sense, period.

The correct game-theoretic statement of 1 knows that 2 knows that E is that E includes P1(P2(w)).

The meet of X and Y is about common knowledge. Saying that E is common knowledge is stronger than saying that 1 knows that 2 knows it. It also implies, for instance, that 2 knows that 1 knows that 2 knows it.