Be on the lookout for those 'unknown unknowns'!
Rumsfeld baffles press with 'unknown unknowns'
The United States Defence Secretary, Donald Rumsfeld, has baffled journalists in Brussels by explaining the greatest threat to Western civilisation may lurk in what he has termed "unknown unknowns".
Mr Rumsfeld says he told a meeting of North Atlantic Treaty Organisation (NATO) defence ministers that even US intelligence agencies can often only see the tip of the iceberg when looking for terrorist threats.
But this is how he explained it at a media conference.
"There are no knowns," Mr Rumsfeld.
"There are things we know that we know. There are known unknowns - that is to say, there are things that we now know we don't know but there are also unknown unknowns. There are things we do not know we don't know," Mr Rumsfeld said.
"So when we do the best we can and we pull all this information together, and we then say well that's basically what we see as the situation, that is really only the known knowns and the known unknowns.
"And each year we discover a few more of those unknown unknowns."