"A bad instructor can go through the entire quarter leaving absolutely nothing memorable in the minds of the students, curve out the scores on an irrelevant test, and leave the impression that some have learned and others have not. But if grades are removed, the class is forced to wonder each day what it’s really learning. The questions, ‘what’s being taught?’ ‘What’s the goal?’ ‘How do the lectures and assignments accomplish the goal?’ Become ominous. The removal of grades exposes a huge and frightening vacuum."
— Robert Pirsig