Where is Donald Rumsfeld when you need him? Here is a page of ‘known unknowns’ and ‘unknown unknowns’, which, on the basis of nothing, I believe to originate in the great country of Brazil. If you know anything about any of them let me know.
As Confucius may, or may not, have said; ”to know that we know what we know, and that we do not know what we do not know, that is true knowledge”. I find that it often helps to drink a strong, flavourful, beer at this point.