There are known knowns

"Known unknown" and "Known unknowns" redirect here. For the House episode, see Known Unknowns.

"Unknown known" and "Unknown knowns" redirect here. For the 2013 documentary film, see The Unknown Known.

"There are known knowns" is a phrase from a response United States Secretary of Defense Donald Rumsfeld gave to a question at a U.S. Department of Defense (DoD) news briefing on February 12, 2002 about the lack of evidence linking the government of Iraq with the supply of weapons of mass destruction to terrorist groups.

Rumsfeld stated:

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 tend to be the difficult ones.

The statement became the subject of much commentary.

Origin

Rumsfeld is often given credit for the phrase, but the idea of unknown unknowns was actually commonly used inside NASA from much earlier. Rumsfeld himself cites NASA administrator William Graham in his memoir. Kirk Borne, an astrophysicist who was employed as a data scientist at NASA Goddard Space Flight Center at the time, notes that he used the phrase "unknown unknowns" in a talk to personnel at the Homeland Security Transition Planning Office a few days prior to Rumsfeld's remarks, and speculates that the term may have percolated up to Rumsfeld and other high-ranking officials in the defense department. The terms "known unknowns" and "unknown unknowns" are current in project management circles. Known unknowns refers to "risks you are aware of, such as cancelled flights...." Unknown unknowns are risks that "come from situations that are so out of this world that they never occur to you. For example, prior to the invention of the personal computer, manufacturers of typewriters probably didn't foresee the risks to their business." Contemporary usage is largely consistent with the earliest known usages. For example, the term was used in evidence given to the British Columbia Royal Commission of Inquiry into Uranium Mining in 1979:

Site conditions always pose unknowns, or uncertainties, which may become known during construction or operation to the detriment of the facility and possibly lead to damage of the environment or endanger public health and safety. The risk posed by unknowns is somewhat dependent on the nature of the unknown relative to past experience. This has led me classify unknowns into one of the following two types: 1. known unknowns (expected or foreseeable conditions), which can be reasonably anticipated but not quantified based on past experience as exemplified by case histories (in Appendix A and 2). Unknown unknowns (unexpected or unforeseeable conditions), which pose a potentially greater risk simply because they cannot be anticipated based on past experience or investigation.

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Known unknowns result from phenomena which are recognized, but poorly understood. On the other hand, unknown unknowns are phenomena which cannot be expected because there has been no prior experience or theoretical basis for expecting the phenomena.

The term also appeared in a 1982 New Yorker article on the aerospace industry, which cites the example of metal fatigue, the cause of crashes in de Havilland Comet airliners in the 1950s.

Reaction

As for the substance of his statement, Rumsfeld's defenders have included Canadian columnist Mark Steyn, who called it "in fact a brilliant distillation of quite a complex matter", and Australian economist and blogger John Quiggin, who wrote, "Although the language may be tortured, the basic point is both valid and important ... Having defended Rumsfeld, I'd point out that the considerations he refers to provide the case for being very cautious in going to war."

Psychoanalytic philosopher Slavoj Žižek says that beyond these three categories there is a fourth, the unknown known, that which we intentionally refuse to acknowledge that we know: "If Rumsfeld thinks that the main dangers in the confrontation with Iraq were the 'unknown unknowns', that is, the threats from Saddam whose nature we cannot even suspect, then the Abu Ghraib scandal shows that the main dangers lie in the "unknown knowns"—the disavowed beliefs, suppositions and obscene practices we pretend not to know about, even though they form the background of our public values."

German sociologists Daase and Kessler (2007) agree with a basic point of Rumsfeld in stating that the cognitive frame for political practice may be determined by the relationship between what we know, what we do not know, what we cannot know, but Rumsfeld left out what we do not like to know.

The event has been used in multiple books to discuss risk assessment.

Rumsfeld named his autobiography Known and Unknown: A Memoir, and The Unknown Known is the title of Errol Morris's 2013 biographical documentary about Rumsfeld.

See also

• Epistemic modal logic
• Dunning–Kruger effect
• I know that I know nothing
• Ignoramus et ignorabimus
• Ignotum per ignotius
• Johari window
• List of political catch phrases
• Ludic fallacy
• Outside Context Problem

External links

• February 12, 2002, Press conference – The reporter asks the question that leads to the "known unknowns" response at approx. 37:19
• DoD News Briefing – Secretary Rumsfeld and Gen. Myer, February 12, 2002 11:30 AM EDT Transcript of the briefing