C. Wright Mills, in The Sociological Imagination:
Teaching, by the way, I do not regard as altogether in the same case as writing. When one publishes a book it becomes a public property; the author's only responsibility to his reading public, if any, is to make it as good a book as he can and he is the final judge of that. But the teacher has further responsibilities. To some extent, students are a captive audience; and to some extent they are dependent upon their teacher, who is something of a model to them. His foremost job is to reveal to them as fully as he can just how a supposedly self-disciplined mind works. The art of teaching is in considerable part the art of thinking out loud but intelligibly. In a book the writer is often trying to persuade others of the result of his thinking; in a classroom the teacher ought to be trying to show others how one man thinks—and at the same time reveal what a fine feeling he gets when he does it well. The teacher ought then, it seems to me, to make very explicit the assumptions, the facts, the methods, the judgments. He ought not to hold back anything, but ought to take it very slowly and at all times repeatedly make clear the full range of moral alternatives before he gives his own choice. To write that way would be enormously dull, and impossibly self-conscious. That is one reason why very successful lectures usually do not print well.
Published in 1959, which goes to explain the gender-specific language, but, but... such a great quote, otherwise. Exactly one week until the start of classes, and very much looking forward to it.