There are four types of people in this world who enter a conversation/ discussion:
1) One who knows not, and himself knows he knows not, is a student. Teach that person.
2) One who knows, and others know he knows, is a teacher. Learn from that person.
3) One who knows, and himself knows not that he knows, is humble. Encourage him.
4) One who knows not, and himself knows not that he knows not, is stupid. Avoid that person. (Note a person who himself thinks he knows, but does not know that he does not know – usually due to arrogance mixed with ignorance)
In any dialogue keep these in mind and you shall be guided to productive discourses.