"There are unknown unknowns" 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. In The Decision Book (2013), author Mikael Krogerus refers to it as the "Rumsfeld matrix". The statement also features in a 2013 documentary film, The Unknown Known, directed by Errol Morris.
