The much-maligned Donald
Rumsfeld, former U.S. Secretary of Defense under President George W. Bush, once
said this: “There are known knowns. These are things we know that we know.
There are known unknowns. That is to say, there are things that we know we don’t
know. But there are also unknown unknowns. There are things we don’t know we
don’t know.”
That may sound like bafflegab, but it’s actually a fairly lucid breakdown of the possibilities.