"Reports that say that something hasn't happened are always interesting to me, because 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."The quote won a "Foot in Mouth" award in 2003 as the most "truly baffling comment" made a public official. The runner-up was Arnold Schwarzenegger saying "I think that gay marriage is something that should be between a man and a woman," meaning that apparently a distinguished panel of judges was more baffled by Rumsfeld's quote than that.
Can I just say: every time I read the Rumsfeld quote, I think, I understand exactly what this is saying, I think it's basically correct*, and not even especially poorly put. I mean, he could have just said, "Things that haven't happened often call attention to matters about which we haven't appreciated our ignorance," but then that wouldn't provide the little set of terms for thinking about it. If anything, I fault him for not completing the 2x2 table and discussing "unknown knowns."
* At least as an epistemological matter, I don't know what concretely about our military situation it was made in reference to.**
** An economist I know upbraided me for using a fancy word when the two of us were talking, saying that she tries to avoid fancy words because she thinks they are just ways academics speak obscurely on purpose as a way of excluding the common masses from discourse. Of course, being an economist, she readily drops "elasticisties" and "externalities" into conversations, as well as using the word "efficiency" in a way that would wildly confuse an untutored member of the common masses. She justifies these words because she says she needs them for precision, a matter about which I would agree (the language of economists is infectious after you start hanging around them precisely because it's precisely useful--or at least that, and the whole economists-run-the-interface-between-social-science-and-any-hope-of-affecting-social-policy thing.) Anyway, the offending "fancy word" prompting this complaint from her was "epistemological."