Life consists of three states of knowledge: the known, which is usual, like a familiar story; the unknown, like a fresh or novel insight in a story; or an unknown unknown, where you can’t grasp what the story is about. 

Language is rich with ways to describe states in time. Tenses are provided that are deeply placed in the structure of sentences. There are sentences in the present, past and future tense and there are also the historical past tense and the subjunctive tense. There are combinations of words to elaborate even further as when it is said that something “could have been”, which is to say something that might have occurred in the past but did not. Which is a subtle description of a condition in time. On the other hand, language has simpler and unelaborated ways of describing kinds of being which are not inflected by time. What is relied on are straightforward assertions, as when Donald Rumsfeld, rhapsodizing about the war on Iraq before it was discovered that there were no weapons of mass destruction, said there were knowns, unknowns and unknown unknowns, the last of the three meaning categories which themselves are unknown. I want to elaborate this obvious three part and well known distinction to apply to a number of actual cases so as to illuminate the actual subject matters that are encountered in everyday life.