George Polya, eminent Hungarian mathematician:

“A teacher of mathematics has a great opportunity. If he fills his alloted time with drilling his students in routine operations he kills their interest, hampers their intellectual development, and misusues his opportunity. But if he callenges the curiosity of his students by setting them problmes proportionate to their knowledge, and helps them to solve their problems with stimulating questions, he may give them a taste for, and some means of, independent thinking.”