The teacher means more than what he teaches.
The teacher is the person who reduces your sense of loneliness whenever it is felt in spite of the interrelations you might have with other men.
It is the loneliness caused by the sheer existence into the world. Any kind of ignorance leaves someone in a state in which he has no support and, therefore, he feels lonely. And any unknown fact about which we are taught is one of the parts of world; for instance, the alphabet is that part of the world consisting in the practice of writing and reading.
The teacher achieves his role of diminishing the loneliness of ignorance before the act of teaching, because when the pupil or the disciple possesses the knowledge, he ceases to be lonely. Also, he forgets that he needed a person for moving away his ignorance.
And the pupil believes in teacher without verifying his competency in teaching the unknown matters.
It’s obviously that there is not a final point of learning, or an end of the feeling of loneliness. Every time, we do not know a great amount of the parts of world. Essentially, those parts of world which are represented by our life and death remain always unknown.
For many, God is a teacher for those parts of the world. But he is needed by men especially for moving away their loneliness and not for the doctrines he is supposed to teach. And his competency of teaching them - as much as his existence - is not really verified.
Moreover, any religious doctrine is claimed without a clear conscience of their supposed divine teacher. Therefore, the harsh defenders of religious doctrines are in fact as lonely as they were before to believe in God. The persistence of such loneliness in the world is testified by the fact that the defenders of religious doctrines use them especially for constituting a community. In other words, they search for replacing the acceptance of the inevitable loneliness in the world with the fight against the loneliness among men, though they are never the same thing.
However, it is true that the social life often makes to be forgotten the loneliness in the world. Likely, the friendship between pupils or disciples diminishes the need of a teacher.