Yea, that's a titillating one.

My favorite is the "You know what you don't know" in that it implies the expressor as having the humility to admit ignorance; which of course, is the beginning of wisdom (imho).

The scariest is the last one, "You don't know what you don't know". This one twists my head just a tad - it kind of humbling also in that, when expressed honestly, shows an acceptance of what hasn't been conceived or even thought of.

Good stuffs...

How can you know what you don't know if you don't know it?

I would amend it as such
You know what you think you know
You think know what you don't know
You don't know what you think you know
and You might know what you think you don't know

Well that would be put under the category of you don't know what you don't know. Personally, I know that I don't know how to play chinese checkers, if that helps you any.

Okay I'll go so far as to amend it some more:

You know what you know (like how to turn on the T.V. (hopefully)
You know what you think you know (Math (yeah it's a problem for me, but Ill admit it)
You know what you don't know (Chinese checkers )
You think you know what you don't know (nuclear physics)
You don't know what you know (recently I found out I was a mediocre drawer)
You don't know what you don't know(recently I found out I know nothing about Nuclear Physic, but now I know I don't know it) lol

I can't help but ask, what do we mean by "know"?

Ahhh, the epistemologist has finally arrived in this thread. It had to happen eventually, chandler ;-) Philosopherqueen, your updated definition seems pretty all-encompassing, good job! I'd split what you don't know you don't know into what you don't know that you don't know (nuclear physics) and what you don't know even exists to be known (the fourth attribute of circuits, for example, was recently proved to exist, and apart from the scientists working on it, very few people even knew to look for it).

God bless iff==> if and only if!