The unknown unknowns
“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, 12 February 2002 At the time, Rumsfeld’s quote, made in response to a reporter’s question about evidence of weapons of mass destruction in Iraq, was seen as a gaffe or else a