"There are known knowns" are the most well-known words of a statement to the press made by the former United States Secretary of Defense Donald Rumsfeld in February 2002.[1]
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| “ | [T]here 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 – there are things we do not know we don't know. |
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The above statement was made by Rumsfeld on February 12, 2002 at a press briefing where he addressed the absence of evidence linking the government of Iraq with the supply of weapons of mass destruction to terrorist groups.[1] It was criticised as an abuse of language by, among others, the Plain English Campaign.[2] However, linguist Geoffrey Pullum disagreed, saying the quotation was "completely straightforward" and "impeccable, syntactically, semantically, logically, and rhetorically."[3]
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",[2] 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."[4]
Italian economists Salvatore Modica and Aldo Rustichini provide an introduction to the economic literature on awareness and unawareness:
| “ | A subject is certain of something when he knows that thing; he is uncertain when he does not know it, but he knows he does not: he is consciously uncertain. On the other hand, he is unaware of something when he does not know it, and he does not know he does not know [emphasis added], and so on ad infinitum: he does not perceive, does not have in mind, the object of knowledge. The opposite of unawareness is awareness.[5] | ” |
Psychoanalytic philosopher Slavoj Žižek extrapolates from these three categories a fourth, the unknown known, that which we intentionally refuse to acknowledge that we know:[6]
| “ | 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. | ” |
Žižek also builds the idea of known unknown, and unknown knowns, into a lecture on The Reality of the Virtual.
The term was in use within the United States military establishment long before Rumsfeld's quote to the press in 2002. An early use of the term comes from a paper entitled "Clausewitz and Modern War Gaming: losing can be better than winning" by Raymond B. Furlong, Lieutenant General, USAF (Ret.) in the Air University Review, July–August 1984:
| “ | To those things Clausewitz wrote about uncertainty and chance, I would add a few comments on unknown unknowns – those things that a commander doesn't even know he doesn't know. Participants in a war game would describe an unknown unknown as unfair, beyond the ground rules of the game. But real war does not follow ground rules, and I would urge that games be "unfair" by introducing unknown unknowns.[7] | ” |
| “ | NASA space exploration should largely address a problem class in reliability and risk management stemming primarily from human error, system risk and multi-objective trade-off analysis, by conducting research into system complexity, risk characterization and modeling, and system reasoning. In general, in every mission we can distinguish risk in three possible ways: a) known-known, b) known-unknown, and c)unknown-unknown. It is probable, almost certain, that space exploration will partially experience similar known or unknown risks embedded in the Apollo missions, Shuttle or Station unless something alters how NASA will perceive and manage safety and reliability.[8] | ” |
From the same time, libertarian lawyer Richard Epstein wrote a well known article in the University of Chicago Law Review about the American labour law doctrine of employment at will (the idea that workers can be fired without warning or reason, unless their contract states terms that are better). In giving some of his reasons in defense of the contract at will, he wrote this:
| “ | The contract at will is also a sensible private adaptation to the problem of imperfect information over time. In sharp contrast to the purchase of standard goods, an inspection of the job before acceptance is far less likely to guarantee its quality thereafter. The future is not clearly known. More important, employees, like employers, know what they do not know. They are not faced with a bolt from the blue, with an "unknown unknown." Rather they face a known unknown for which they can plan. The at-will contract is an essential part of that planning because it allows both sides to take a wait-and-see attitude to their relationship so that new and more accurate choices can be made on the strength of improved information.[9] | ” |
In a 2010 Washington Times interview, Admiral James A. Winnefeld, Jr., commander of the United States Northern Command, says he is most worried about "the unknown unknowns."[10]
Rumsfeld used the quote in the title of his autobiography Known and Unknown: A Memoir.
The concept of Unknown Unknowns is also similar to the Relevance paradox where decision makers think they have obtained all relevant information, but are unaware of the existence of certain relevant information, because its relevance is not apparent until they have that information.
A Persian-Tajik thirteenth-century poet Ibn Yamin (Ibn Yamin Faryumadi)(ابن یمین فریومدی), born 1286 in Faryumad near Sabzevar and died 1368, says there are four types of men[11][12]:
آنکس که بداند و بداند که بداند
اسب خرد از گنبد گردون بجهاند
آنکس که بداند و نداند که بداند
بیدار کنیدش که بسی خفته نماند
آنکس که نداند و بداند که نداند
لنگان خرک خویش به منزل برساند
آنکس که نداند و نداند که نداند
در جهل مرکب ابدالدهر بماند
Since Rumsfeld's speech, both the full quote and the term "unknown unknowns" have appeared in popular culture.