'..something is wrong but you will never know what it is..'

I am reading Errol Morris's article in the NYT and he quoted Donald Rumsfeld about “unknown unknowns.”

           'It goes something like this: “There are things we know we know about terrorism.  There are things we know we don’t know.  And there are things that are unknown unknowns.  We don’t know that we don’t know.”

he then goes on to say

         Rumsfeld’s famous “unknown unknowns” quote occurred in a Q&A session at the end of a NATO press conference. A reporter asked him, “Regarding terrorism and weapons of mass destruction, you said something to the effect that the real situation is worse than the facts show…”  Rumsfeld replied, “Sure.  All of us in this business read intelligence information.  And we read it daily and we think about it, and it becomes in our minds essentially what exists.  And that’s wrong.  It is not what exists.”

As Errol Morris himself says, 'what will it cost me to know less?'