When you don't know that you don't know, it's a lot different than when you do know that you don't know.

When you don't know that you don't know, it's a lot different than when you do know that you don't know.

当你不知道你不知道的时候，和你知道你不知道的时候有很大的不同。

-- Bill Parcells 帕索斯