Who said this?
	文章来源: 屋漏痕 于 2007-10-11 10:15:03

… because 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.