“[T]here 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—there are things we do not know we don’t know.” —Donald Rumsfeld
“Rumsfeld’s famous line about “unknown unknowns,” delivered in a 2002 press conference in response to a reporter’s question about the presence of weapons of mass destruction in Iraq, is a corollary to Schelling’s concern about mistaking the unfamiliar for the unlikely.
If we ask ourselves a question and can come up with an exact answer, that is a known known. If we ask ourselves a question and can’t come up with a very precise answer, that is a known unknown. An unknown unknown is when we haven’t really thought to ask the question in the first place. “They are gaps in our knowledge, but gaps that we don’t know exist,””
“Still, as the 9/11 Commission deduced, the most important source of failure in advance of the attacks was our lack of imagination.”
The point being, the signals were there, but we either didn’t see them or didn’t have the will to overcome the organizational inertia to deal with the signal’s implications.
and to Schelling’s point:
“There is a tendency in our planning to confuse the unfamiliar with the improbable. The contingency we have not considered seriously looks strange; what looks strange is thought improbable; what is improbable need not be considered seriously.”
From Nate Silver, The Signal and the Noise