Donald Rumsfeld on US policy on the war on terror, 3/07/2003

"There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know and there things that we don't know. But there are also unknown unknowns. There are things we don't know we don't know."
-- Donald Rumsfeld, clarifying U.S. policy on the war on terror at a Pentagon briefing.