From my desk calendar at work:There are known knowns. There are things we know that we know.
There are known unknowns. That is to say, there are things that we know we don't know.
But there are also unknown unknowns. There are things we don't know that we don't know.
Defense Secretary Donald Rumsfeld, trying to clarify the war on terrorism, during a Pentagon briefing.
posted by Laurie Kay Ransonette Anderson at 10/17/2005 07:01:00 PM