The unofficial poet laureate of the Bush administration, Donald Rumsfeld, wrote a stirring piece on this very idea in 2002:
The Unknown, by Donald Rumsfeld (2002)
As we know,
There are known knowns.
There are things we know we know.
We also know
There are known unknowns.
That is to say
We know there are some things
We do not know.
But there are also unknown unknowns,
The ones we don’t know
We don’t know.
I have always been a fan of Don Rumsfeld’s poetry. If the English language still exists 500 years from now, people will still be studying his poems. In addition to his work with the English language, he has also been a pioneer in the field of martial arts and has developed a variety of innovative fighting techniques.