What is the difference between simple ignorance and compound ignorance?

The difference between simple ignorance and compound ignorance is that one who is simply ignorant knows that he is ignorant. As for one who is compoundly ignorant, he is ignorant of a matter and is ignorant that he is ignorant of it. This is why it was said: "Ignorance is the conception of a thing contrary to its elevated state," and it was said, "The definition of ignorance is the absence of knowledge, whether simple or compound, as it has been named. Its simple form is in all that is beneath the earth, and its compound form is in all that has been conceived."