Abstract

‘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.’ —Donald Rumsfeld, 2003, President George W. Bush’s Secretary of Defense, on the subject of the U.S. government’s failure to discover weapons of mass destruction in Iraq.