Little et al. and reported a number of times in the literature since then as a general approach. See also Black swan theory Dunning–Kruger effect 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 "Known Unknowns" Outside Context Problem Russell's teapot Undecidable problem The Unknown Known Wild card (foresight) References External links American phraseology Epistemology Political quotes Unknown content Ignorance 2002 neologisms Donald Rumsfeld