Imam Ali (as) in one of his categorizations of people,
They are of four types:
1. One who knows and he knows that he knows, he is a scholar, take from him.
2. One who knows but he does not know that he knows, he is in a slumber, awaken him.
3. One who does not know but he knows that he does not know, that is a student, teach him.
4. One who does not know but he does not know that he does not know, he is ignorant, stay away from him.