Malcolm Gladwell in The New Yorker:
The national-security expert Gregory Treverton has famously made a distinction between puzzles and mysteries. Osama bin Laden’s whereabouts are a puzzle. We can’t find him because we don’t have enough information. The key to the puzzle will probably come from someone close to bin Laden, and until we can find that source bin Laden will remain at large.
The problem of what would happen in Iraq after the toppling of Saddam Hussein was, by contrast, a mystery. It wasn’t a question that had a simple, factual answer. Mysteries require judgments and the assessment of uncertainty, and the hard part is not that we have too little information but that we have too much. The C.I.A. had a position on what a post-invasion Iraq would look like, and so did the Pentagon and the State Department and Colin Powell and Dick Cheney and any number of political scientists and journalists and think-tank fellows. For that matter, so did every cabdriver in Baghdad.
The distinction is not trivial. If you consider the motivation and methods behind the attacks of September 11th to be mainly a puzzle, for instance, then the logical response is to increase the collection of intelligence, recruit more spies, add to the volume of information we have about Al Qaeda. If you consider September 11th a mystery, though, you’d have to wonder whether adding to the volume of information will only make things worse. You’d want to improve the analysis within the intelligence community; you’d want more thoughtful and skeptical people with the skills to look more closely at what we already know about Al Qaeda. You’d want to send the counterterrorism team from the C.I.A. on a golfing trip twice a month with the counterterrorism teams from the F.B.I. and the N.S.A. and the Defense Department, so they could get to know one another and compare notes.