The scene is a lecture room in a Medical Faculty of a University. The eminent Professor of Medicine is addressing the students at the end of the last lecture before their final exams.
“Ladies and gentlemen,” he says, “I congratulate you all on completing my course of lectures. I wish you all well in your future honorable profession. That leaves only two more thing to say.
“The first is this. Half of the things I have taught you as medical facts are, in fact, false!
“The second is that neither I nor anyone else today knows which half!”