There are unknown unknowns

Rumsfeld's statement brought attention to the concepts of known knowns, known unknowns, and unknown unknowns, but these were in common use in US defense procurement by the late 1960s.

In a 1968 study sponsored by the Aerospace Industries Association, Hudson Drake from North American Rockwell argued that defence contractors had to solve both known unknowns and "unanticipated unknowns".{{Cite book |title=History of Acquisition in the Department of Defence, Volume 2, Adapting to Flexible Response 1960-1968 |date=2013 |last=Poole |first=Walter S. |chapter=Chapter IV – Innovation: Coping with 'Unanticipated Unkowns' |page=95 |chapter-url=https://archive.org/details/adaptingtoflexib0002walt_i6x8/page/95/mode/1up}}

Also in 1968, Lt. Gen. William B. Bunker noted that when developing complex weapons systems "there are two kinds of technical problems: there are the known unknowns, and the unknown unknowns."{{Cite journal |title=The 'Known Unknowns' And The 'Unknown Unknowns' |journal=Armed Force Journal |date=1968-12-07 |last=Andrews |first=Walter| volume=106| issue=15|pages=14–15 |url=https://archive.org/details/sim_armed-forces-journal_1968-12-14_106_15}}

The usage was common enough for an industry shorthand to have developed where unknown-unknowns were referred to as "unk-unks".{{Cite journal |title=For Lockheed, Everything's Coming Up Unk-Unks |journal=Fortune |date=1969-08-01 |last=Meyers |first=Harald B. |volume=80 |issue=2| page=76}}

The term was commonly used inside NASA.{{Cite web | url=https://books.google.com/books?id=dRMrAAAAMAAJ&q=%22unknown+unknowns%22&pg=PA73 |title = NASA Program Management and Procurement Procedures and Practices: Hearings Before the Subcommittee on Space Science and Applications of the Committee on Science and Technology, U.S. House of Representatives, Ninety-seventh Congress, First Session, June 24, 25, 1981 |year = 1981 |publisher=U.S. Government Printing Office}} Rumsfeld cited NASA administrator William Graham in his memoir; he wrote that he had first heard "a variant of the phrase" from Graham when they served together on the Commission to Assess the Ballistic Missile Threat to the United States during the late 1990s.{{cite book|last1=Rumsfeld|first1=Donald|title=Known and Unknown: A Memoir|date=2011|publisher=Penguin Group|location=New York|isbn=9781101502495|page=xiv|url=https://books.google.com/books?id=_wIcpxMOjD4C&pg=PT15}}

Rumsfeld had previously publicly used the terms himself, stating in a 2000 speech that "There are known knowns, known unknowns and unknown unknowns. Effective intelligence work must consider them all."{{cite book |first=Donald H. |last=Rumsfeld |title= Remarks of the Honorable Donald H. Rumsfeld Prepared for delivery, Community Forum Series: The New National Security Environment |location=Bryn Mawr, Pennsylvania |date=8 February 2000 |pages=194–203 |url=https://books.google.com/books?id=BZYZAAAAIAAJ&dq=%22unknown+unknowns%22+%22known+knowns%22+%22known+unknowns%22&pg=PA200 |series=Nominations Before the Senate Armed Services Committee, First Session, 107th Congress |publisher=U.S. Government Printing Office|isbn=978-0-16-069297-0 }}

The terms "known unknowns" and "unknown unknowns" are often used in project management and strategic planning{{Cite journal | url=https://hbr.org/1997/11/strategy-under-uncertainty | title=Strategy Under Uncertainty| journal=Harvard Business Review| date=November 1997| last1=Courtney| first1=Hugh| last2=Kirkland| first2=Jane| last3=Viguerie| first3=Patrick| volume=75| issue=6| pages=66–79| pmid=10174798}} circles.

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:

{{Blockquote|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 to 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.

Known unknowns result from recognized but poorly understood phenomena. 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.{{cite book |url=http://www.empr.gov.bc.ca/Mining/Geoscience/PublicationsCatalogue/Papers/Pages/1980-7.aspx |title=Statement of Evidence of E. D'Appolonia, D'Appolonia Consulting Engineers, Pittsburgh, Pennsylvania |series= Proceedings of the British Columbia Royal Commission of Inquiry into Uranium Mining |chapter=Phase V: Waste Disposal |year=1979 |id=0005037606 |isbn=978-0-7718-8198-5}}}}

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.{{citation |last= Newhouse |first= J. |date= June 14, 1982 |title= A reporter at large: a sporty game; 1-betting the company |work= New Yorker |url=https://www.newyorker.com/magazine/1982/06/14/a-sporty-game-i-betting-the-company |pages= 48–105}}.

Canadian columnist Mark Steyn called it "in fact a brilliant distillation of quite a complex matter".{{cite news |author=Steyn, Mark |author-link=Mark Steyn |url=https://www.telegraph.co.uk/comment/personal-view/3599959/Rummy-speaks-the-truth-not-gobbledygook.html |title=Rummy speaks the truth, not gobbledygook |publisher=Daily Telegraph |date=December 9, 2003 |access-date=October 30, 2008}} Australian economist and blogger John Quiggin wrote: "Although the language may be tortured, the basic point is both valid and important."{{cite web |last=Quiggin |first=John |author-link=John Quiggin |url=https://johnquiggin.com/2004/02/10/in-defense-of-rumsfeld/ |title=In Defense of Rumsfeld |work=johnquiggin.com |access-date=5 January 2024 |date=February 10, 2004}}

Psychoanalytic philosopher Slavoj Žižek says that beyond these three categories there is a fourth, the unknown known, that which one intentionally refuses to acknowledge that one knows: "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."{{cite web |url=https://www.lacan.com/zizekrumsfeld.htm |date=May 21, 2004 |work=In These Times |via=lacan.com |first=Slavoj |last=Žižek |author-link=Slavoj Žižek |title=What Rumsfeld Doesn't Know That He Knows About Abu Ghraib |access-date=February 23, 2009}}

German sociologists Christopher Daase and Oliver Kessler agreed 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 stated that Rumsfeld left out "what we do not like to know".{{Cite journal |last1=Daase |first1=Christopher |last2=Kessler |first2=Oliver |date=December 2007 |title=Knowns and Unknowns in the 'War on Terror': Uncertainty and the Political Construction of Danger |url=http://journals.sagepub.com/doi/10.1177/0967010607084994 |journal=Security Dialogue |language=en |volume=38 |issue=4 |pages=411–434 |doi=10.1177/0967010607084994 |s2cid=145253344 |issn=0967-0106}}

The event has been used in multiple books to discuss risk assessment.{{cite book|last1=Neve|first1=Geert de|last2=Luetchford|first2=Peter|title=Hidden Hands in the Market: Ethnographies of Fair Trade, Ethical Consumption, and Corporate Social Responsibility |url=https://books.google.com/books?id=M1iYFfhhm8cC&pg=PA252|access-date=February 10, 2014 |year=2008 |publisher=Emerald Group Publishing |isbn=9781848550582|pages=252–}}

Rumsfeld named his 2011 autobiography Known and Unknown: A Memoir. In the author's note at the start of the book, he expressly acknowledges the source of his memoir's title and mentions a few examples of his statement's prominence.{{cite book|last1=Rumsfeld |first1=Donald |title=Known and Unknown: A Memoir|date=2011|publisher=Penguin Group|location=New York|isbn=9781101502495|page=xiii|url=https://books.google.com/books?id=_wIcpxMOjD4C&pg=PR14}} The Unknown Known is the title of Errol Morris's 2013 biographical documentary film about Rumsfeld.{{cite news |author=Scott|title=Not Giving an Inch in a Battle of Wits and Words; Deciphering Donald H. Rumsfeld in 'The Unknown Known'|url=https://www.nytimes.com/2014/04/02/movies/deciphering-donald-h-rumsfeld-in-the-unknown-known.html|access-date=April 4, 2014|year=2014|newspaper=The New York Times}} In it, Rumsfeld initially defines "unknown knowns" as "the things you think you know, that it turns out you did not", and toward the end of the film he defines the term as "things that you know, that you don't know you know".Morris, Errol (Director) (December 13, 2013). The Unknown Known (Motion picture). Los Angeles, CA: The Weinstein Company.

Rumsfeld's comment earned the 2003 Foot in Mouth Award from the British Plain English Campaign.{{cite news |url=http://news.bbc.co.uk/1/hi/3254852.stm |title=Rum remark wins Rumsfeld an award |work=BBC News |date=2 December 2003 |access-date=30 September 2012}}

As alluded to by Rumsfeld in his autobiography,{{r|Rumsfeld2|p=xv}} over two millenia ago Socrates considered known unknowns and unknown unknowns.{{cite book |title=Dangerous Science: Science Policy and Risk Analysis for Scientists and Engineers |first=Daniel J. |last=Rozell |date=2020 |isbn=9781911529897 |publisher=Ubiquity Press |page=48 |url=https://books.google.com/books?id=9iTUDwAAQBAJ&pg=PA48}}{{cite book |title=The SAGE Handbook of Philosophy of Education |date=March 23, 2010 |page=304 |editor-first1=Christine |editor-last1=McCarthy |editor-first2=David |editor-last2=Carr |editor-first3=Richard |editor-last3=Bailey |editor-first4=Robin |editor-last4=Barrow |url=https://books.google.com/books?id=FI02oTvjkV8C&dq=%22unknown+unknowns%22+%22socrates%22&pg=PA304 |isbn=9781446206973}}

Much later, Thomas Aquinas in his Summa Theologica also emphasized the important difference between recognized ignorance and unconscious ignorance.{{cite encyclopedia |last=Nugent |first=J.B. |date=1967 |title=Ignorance |encyclopedia=New Catholic Encyclopedia |location=New York |publisher= McGraw-Hill Book Company |url=https://archive.org/details/newcatholicencyc0007unse_y2j2/page/356/mode/1up?q=%22unrecognized+ignorance%22 |access-date=2025-03-13}}

Rumsfeld's statement closely parallelled a well-known proverb about knowledge:{{cite book |editor-first=Tom |editor-last=Sumner |first=Geoffrey K. |last=Pullum |author-link=Geoffrey K. Pullum |chapter=No foot in mouth |title=Untidy: The Blogs on Rumsfeld |page=28 |date=2005|publisher=William, James & Co. |location=Wilsonville, Oregon |chapter-url=https://books.google.com/books?id=ITFxygayVrMC&pg=PA28 |isbn=9781590280478}}{{r|Saravanan2021|p=200}} {{Blockquote|

}}

This has been widely quoted{{cite book |url=https://archive.org/details/familiarquotatio00bart/page/754/mode/1up?q=%22he+who+knows+not%2C+and+knows+not%22

|title=Familiar Quotations: a collection of passages, phrases, and proverbs traced to their sources in ancient and modern literature |first=John |last=Bartlett |date=1955 |page=754 |edition=13 |publisher=Little, Brown |location=Boston}} since the 19th century as (for example) an anonymous

Persian,{{cite book |title=The Best Loved Poems of the American People |page=623 |date=1936 |editor-first=Hazel |editor-last=Felleman |publisher=Garden City Books |location=Garden City, New York |url=https://archive.org/details/bestlovedpoemsof0000unse_f7n3/page/623/mode/1up}}{{cite book |title=The American Citizens Handbook|page=371 |date=1951 |editor-first=Joy Elmer |editor-last=Morgan |publisher=National Education Association of the United States |url=https://archive.org/details/americancitizens00morg/page/371/mode/1up?q=%22he+who+knows+not%22}}

Arabic,{{cite news |date= 15 December 1885 |title=A Knowsy Proverb |url=https://www.proquest.com/docview/1537072880/sem-2 |page=6 |work=The Globe |location=Toronto |access-date=19 March 2025}}{{cite book |url=https://archive.org/details/lifeofcaptainsir01burtuoft/page/548/mode/1up |first=Isabel |last=Burton |title=The Life of Sir Richard F. Burton, K.C.M.G., F.R.G.S. |date=1893 |publisher=Chapman & Hall |location=London |page=548 |access-date=19 March 2025}}

African,{{cite book |title=Daily Motivations for African-American Success |first=Dennis |last=Kimbro |publisher=Random House - Fawcett Books |location=New York |date=1993 |chapter= September 4: Sesame Street |isbn=9780449223253 |chapter-url=https://books.google.com/books?id=LhfrupUOQY8C&dq=%22shun+him%22+%C2%A0%22teach+him%22&pg=RA7-PA4}}

Japanese,{{cite news |page=21 |date=6 February 1907 |work=Presbyterian Standard |title=Japanese Proverbs |volume=XLVI |issue=53 |location=Charlotte, N.C.|url=https://archive.org/details/presbyterianstan47pres_1/page/n184/mode/1up}}

Oriental{{cite book |page=55 |title=Learning support : a guide for mature students |first=Elizabeth |last=Hoult |date=2006 |publisher=Sage Publications |isbn=9781412902946 |url=https://archive.org/details/learningsupportg0000houl/page/55/mode/1up}}

or simply an old{{cite magazine |first=Margaret Sutton |last=Driscoe |date= 22 December 1894 |volume=27 |issue=51 |title=The Days We Live In |url=https://archive.org/details/sim_harpers-bazaar_1894-12-22_27_51/page/n10/mode/1up?q=%22he+who+knows+not%2C+and+knows+not+that+he+knows+not%22 |page=6 |magazine=Harper's Bazaar |access-date=19 March 2025}} proverb, or

attributed to authors ranging from Confucius {{cite news |last=Dixon |first=Michael |date= 16 April 1993 |title=A case of the worst sort of ignorance |url=https://archive.org/details/FinancialTimes1993UKEnglish/Apr%2016%201993%2C%20Financial%20Times%2C%20%231013%2C%20UK%20%28en%29/page/n21/mode/1up |page=22 |work=Financial Times |location=London |access-date=19 March 2025}}

to Bruce Lee.{{cite magazine |date= 1993 |issue=Fall/Winter |title=Bruce Lee: A Visit to the Grave |url=https://archive.org/details/grand-royal-01-1993-dregs-ia/page/n46/mode/1up |page=50 |magazine=Grand Royal Magazine |location=Los Angeles |access-date=19 March 2025}}

The proverb is actually a close translation (with line order reversed) of al-Khalil ibn Ahmad al-Farahidi's medieval epigram about the "four kinds of men", as reported by Al-Ghazali (1058-1111 CE),{{cite book |language=arabic |author-link=Al-Ghazali |first=Muhammad Hamid |last=Al=Ghazali |pages=87–88 |chapter=الباب السادس في آفات العلم وبيان علامات علماء الآخرة والعلماء السو |title=كتاب: إحياء علوم الدين کتاب العلم |date=June 25, 2013 |chapter-url=https://archive.org/details/KitabAhyaaUloomuddinKitabulIlmLiImamMuhammadHamidAlGhazaliArabicTextBookOfKnowledge/page/n85/mode/2up}}{{cite book |title=Revival of the Religion's Sciences |translator-first=Mohammad Mahdi |translator-last=al-Sharif |first=Abu Hamed |last=Al-Ghazali |date=2011 |author-link=Al-Ghazali |publisher=Dar Al-Kotob Al-ilmiyah |location=Beirut, Lebanon |url=https://archive.org/details/imam-abu-hamid-al-ghazali-ulum-al-din-revivication-of-the-islamic-sciences-vol-1/Imam%20abu%20Hamid%20al-Ghazali%20-%20Ulum%20al-Din%20-%20Revivication%20of%20the%20Islamic%20Sciences%20-%20vol%201%20of%204%20%282011%2C%20Dar%20ul-Kutub%20al-Ilmiyah%29/page/115/mode/1up |page=115|isbn=978-2-7451-5945-8}}

which was later echoed in poems by Nasir al-Din al-Tusi{{cite book |url=https://archive.org/details/historyofiranemp0000axwo/page/n14/mode/1up?q=%22knows+that+he+knows%22 |title=A history of Iran : empire of the mind |last=Axworthy |first=Michael |date=2008 |publisher=Basic Books |location=New York |isbn=978-0-465-00888-9}} and Ibn Yamin.{{cite book |page=315 |url=https://archive.org/details/classicalpersian0000ajar_t8t6/page/315/mode/1up?q=%22knows+not+and+knows+not%22 |title=Classical Persian Literature |first=A.J. |last=Arberry |date=1958 |publisher=George Allen & Unwin Ltd. |location=London |isbn=9780203985434}}

"Unknown unknowns" were occasionally mentioned in the 1950s and 60s.

In 1950, it was noted that sociology research was full of "unknown unknowns".{{Cite journal | url=https://www.jstor.org/stable/23705367 | title=The research project: Its educational value and its contribution to social work knowledge| journal=Social Work Journal| date=July 1950| last=Gordon| first=William E| volume=31| issue=3| pages=110–116| jstor=23705367}} In a 1962 commencement address, Nobel laureate biochemist Melvin Calvin discussed how humanity "must grapple not only with the known and the 'known unknown', but also with the vastness of the 'unknown unknown'."{{Cite news |url=https://archive.org/details/ucladailybruin40losa/page/n484/mode/1up |date=15 June 1962 |title=University Responding to Challenges |work=UCLA Summer Bruin |page=2}}

A related 2x2 grid was created in 1955 by two American psychologists, Joseph Luft and Harrington Ingham in their development of the Johari window, a "graphic model of interpersonal behaviour"{{cite book |url=https://archive.org/details/ofhumaninteracti00jose/page/5/mode/1up |first=Joseph |last=Luft |title=Of human interaction |date=1969 |publisher=National Press Book|isbn=978-0-87484-134-3 }} that classifies knowledge about your behavior and motivations in terms of whether you or others are aware of those behaviours or motivations. For example, your motivation might be (un)known by you and (un)known by others.

Another similar{{cite journal |title=COVID-19: a knowledge and learning perspective |first1=Nicole |last1=Tovstiga |first2=George |last2=Tovstiga |journal=Knowledge Management Research & Practice |volume=19 |issue=4 |date=2021 |pages=427–432|doi=10.1080/14778238.2020.1806749

|url=https://www.researchgate.net/publication/343874359}} classification scheme is the conscious competence learning model published in 1960, where a person's knowledge and skills are classified according to how (un)conscious and (in)competent they are.{{cite book |page=69 |title=Management of Training Programs |date=1960 |last1=DePhillips |first1=Frank A. |last2=Berliner |first2=William M. |last3=Cribbin |first3=James J. |publisher=Richard C. Erwin, Inc. |location=Homewood, Illinois}}

The term "known unknowns" has been applied to the identification of chemical substances using analytical chemistry approaches, specifically mass spectrometry. In many cases, an unknown to an investigator that is detected in an experiment is actually known in the chemical literature, a reference database, or an Internet resource. These types of compounds are termed "known unknowns". The term was originally coined by Little et al.{{cite journal |last1=Little |first1=J.L. |last2=Cleven |first2=C.D. |last3=Brown |first3=S.D. |year=2011 |title=Identification of "Known Unknowns" utilizing accurate mass data and chemical abstracts service databases |journal=J. Am. Soc. Mass Spectrom. |volume=22 |issue=2 |pages=348–359 |doi=10.1007/s13361-010-0034-3 |pmid=21472594 |bibcode=2011JASMS..22..348L |doi-access=free }} and reported a number of times in the literature since then as a general approach.{{cite journal |title=Identification of "known unknowns" utilizing accurate mass data and ChemSpider |doi=10.1007/s13361-011-0265-y |pmid=22069037 |volume=23 |issue=1 |journal=Journal of the American Society for Mass Spectrometry |pages=179–185 |year=2011 |last1=Little |first1=James L. |doi-access=free }}{{cite journal |last1=Stein |first1=S. |year=2012 |title=Mass Spectral Reference Libraries: An Ever-Expanding Resource for Chemical Identification |journal=Analytical Chemistry |volume=84 |issue=17 |pages=7274–7282 |doi=10.1021/ac301205z |pmid=22803687 }}{{cite journal |title=Identifying known unknowns using the US EPA's CompTox Chemistry Dashboard |doi=10.1007/s00216-016-0139-z |pmid=27987027 |volume=409 |issue=7 |journal=Analytical and Bioanalytical Chemistry |pages=1729–1735 |year=2016 |last1=McEachran |first1=Andrew D. |last2=Sobus |first2=Jon R. |last3=Williams |first3=Antony J. |s2cid=31754962 }}{{cite journal |last1=Schymanski |first1=Emma L. |author-link=Emma Schymanski |last2=Williams |first2=Antony J. |year=2017 |title=Open Science for Identifying "Known Unknown" Chemicals |journal=Environmental Science and Technology |volume=51 |issue=10 |pages=5357–5359 |bibcode=2017EnST...51.5357S |doi=10.1021/acs.est.7b01908 |pmc=6260822 |pmid=28475325}}

{{div col|colwidth=22em}}

• Black swan theory
• Cynefin framework
• Dunning–Kruger effect
• Emic and etic
• Epistemic modal logic
• Four stages of competence
• I know that I know nothing
• Ignoramus et ignorabimus
• Ignotum per ignotius
• Johari window
• Knightian uncertainty
• Known and Unknown: A Memoir
• Outside Context Problem
• Russell's teapot
• Undecidable problem
• The Unknown Known
• Wild card (foresight)
• Argument from ignorance

{{div col end}}

{{Reflist|30em}}

• {{cite web |url=https://www.c-span.org/video/?168646-1/defense-department-briefing |date= February 12, 2002 |title= Defense Department Briefing |quote=
  Reporter:^37:19 ...Because there are reports that there is no evidence of a direct link between Baghdad and some of these terrorist organizations.
  Rumsfeld: Reports that say that something hasn't happened are always interesting to me... |publisher= C-SPAN}}
• {{cite journal |title= Known knowns, known unknowns, unknown unknowns and the propagation of scientific enquiry |first=David C.|last= Logan|journal= Journal of Experimental Botany |volume= 60 |issue= 3 |pages= 712–4|date=March 1, 2009|doi= 10.1093/jxb/erp043 |pmid = 19269994|doi-access= free}}

{{Iraq War}}

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