purpose of teaching

In this interview, along other things, Noam Chomsky explains that a teacher should not try to convince the students that he/she is right but to motivate them to think about the subject in order to find the truth themselves which sometimes is that he/she is wrong. And if a teacher or speaker has this talent of being persuasive by appealing to people's emotions they should avoid using it because it undermines their capacity for independent thinking.

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Later edit:

Also, here's a quote from Dead Poets Society movie:

"I always thought the idea of education was to learn to think for yourself."

Here are others from the same movie.