The trouble is that many people regard disagreement as unrelated to either teaching or being taught. They think that everything is just a matter of opinion. I have mine, and you have yours; and our right to our opinions is as inviolable as our right to private property. On such a view, communication cannot be profitable if the profit to be gained is an increase in knowledge. Conversation is hardly better than a ping-pong game of opposed opinions, a game in which no one keeps score, no one wins, and everyone is satisfied because he does not lose - that is, he ends up holding the same opinions he started with.
Mortimer J. Adler, How to Read a Book: The Classic Guide to Intelligent Reading
conversation, opinions