Former Defence Secretary of the United States, Donald Rumsfeld’s most famous quote is about knowing what you know, and knowing what you don’t know…and then not knowing other things you don’t know. A lot of people made fun of it, but it’s an accurate and smart comment.
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.