One way to think about risks is in terms of uncertainty.
Donald Rumsfeld, United States Secretary of Defense, explains the limitations of intelligence reports and issues surrounding risk-based decisions.
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.Donald Rumsfeld