Let me give credits to US Defense Secretary Rumsfield before anyone accuses me of stealing the word - "unknown unknowns" ----------------------------------------------------------------------------------------------------- As we know, 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. - Feb. 12, 2002, Department of Defense news briefing