Almost exactly 5 months after the Sept. 11, 2001, attacks on the United States, then-Secretary of Defense Donald Rumsfeld began advocating for military action against Iraq, alleging that Saddam Hussein was stockpiling “weapons of mass destruction,” or WMDs—an acronym that quickly became ubiquitous. President George W. Bush supported this justification, arguing explicitly by early 2002 that action was necessary to prevent Middle Eastern regimes from potentially transferring WMDs to terrorist groups.
A reporter asked Rumsfeld at a Feb. 12, 2002, press conference if there was “any evidence to indicate that Iraq has attempted to or is willing to supply terrorists with weapons of mass destruction?” Rumsfeld’s response introduced the concept of “unknown unknowns” when he replied, “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. And if one looks throughout the history of our country and other free countries, it is the latter category that tends to be the difficult ones” (https://web.archive.org/web/20160406235718/http:/archive.defense.gov/Transcripts/Transcript.aspx?TranscriptID=2636).
This struck the national zeitgeist with an unexpected force, possibly for a few reasons:
1. It was great fodder for late-night talk shows. The jokes practically wrote themselves.
2. It’s an interesting idea. The op-eds practically wrote themselves.
3. The category of unknown unknowns gives us an excuse for some of our own mistakes: Your restaurant should have a contingency plan in case its soft ice cream machine breaks down, but no one can fault you if aliens turn all dairy products into shampoo. The concept of unknown unknowns provides us with some cover for not anticipating changes that are impossible to predict.
But does it actually provide cover? Rumsfeld’s implication seems to be that you can’t hold him responsible for not knowing if there are secret alliances among governments and terrorist groups, but is this ignorance enough to justify invading a country? What a dangerous precedent that usage of unknown unknowns would set: “We can’t know, so ... let loose the dogs of war!”
In fact, as the reporter who asked the question immediately responded, not knowing if governments are supplying terrorists with WMDs doesn’t sound like an unknown unknown at all: Since Rumsfeld knows he doesn’t know about these secret alliances, aren’t they known unknowns? Rumsfeld responded by saying, "i'm not going to say which it is,” thus generating yet another known unknown.
What Truly Is an Unknown Unknown?
So, what constitutes a truly unknown unknown? Alien mutation of dairy products, for sure. But more realistically, the nature of gravity as a force correlated with mass was an unknown unknown until Newton came along. Before then, we didn’t know that we didn’t know that. Maybe germ theory in the 19th century counts. Maybe the success of impressionism in the 19th and early 20th centuries. These were all massively significant transformations that could not be predicted until they occurred. These ways of seeing the world—scientifically and aesthetically—were unknown unknowns until they happened because we didn’t suspect there was anything there to know.