The Unknown:

"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." [Department of Defense news briefing Feb. 12, 2002]

Now, imagine it set to music and sung aloud by a classically trained female singer with a beautiful voice.More info and downloads. Found at www.metafilter.com