There are known knowns

"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:

The statement became the subject of much commentary, including a documentary by Academy Award winning director Errol Morris.

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: