A person who doesn't know, but knows he doesn't know is a student; teach him.
A person who knows but who doesn't know he knows is asleep; awaken him.
But a person who knows and knows that he knows is wise; follow him.
-Old Asian Proverb.

More importantly, a person who doesn't know and doesn't know he doesn't know is a pain in the ass; avoid him at all costs.
-Personal Commentary of Greg Mote on the Old Asian Proverb.