If you ask a living teacher a question, he will probably answer you. If you are puzzled by what he says, you can save yourself the trouble of thinking by asking him what he means. If, however, you ask a book a question, you must answer it yourself. In this respect a book is like nature or the world. When you question it, it answers you only to the extent that you do the work of thinking an analysis yourself.

Autore: Mortimer J. Adler