There are known knowns; there are things we know we know. We also know there are known unknowns; that is to say, we know there are some things we do not know. But there are also unknown unknowns — the ones we don't know we don't know.
+14 Vote for this quoteVote against this quote 0
+ add attribution

submitted by purpleparrot, December 27, 2010
Donald Rumsfeld
This quote was added November 29, 2007.