"There was allegedly an exception when one German professor praised the habit of asking Ph.D. students “unsolvable question” at their oral exams. If the student instantly said, “That's unsolvable”, he was deemed to have the right sharp set of mind. The professor put his favorite unsolvable equations on the blackboard as an illustration. Johnny muttered at the ceiling for a few minutes, and then solved some of them. A more typical occasion was when one professor propounded a new discovery that was actually quite wrong. This wrongdoer handled all the questions at the seminar devastatingly well, and there was discussion of his discovery at a private dinner that night. Johnny demolished the whole discovery by saying that he should have been asked a, b, and c . “Why didn't you ask that?” said the seminar organizer desperately. Johnny intimated that he did not like to be publicly rude."