Human beings are of four types:

1. A man who knows, and knows that he knows. This is the scholar, so take and patiently learn from him.

2. A man who knows, but does not know that he knows. This one has forgotten, so quietly remind him.

3. A man who does not know, and knows that he does not know. This one is a student, so teach him continuously because he will be a great scholar one day.

4. A man who does not know, and does not know that he does not know and isn't even interested in knowing. This one is an idiot, so reject him".