I swear the following story is true, though I don't know if I'd believe it myself, if it came from someone else.

Back when I was a beginning grad student, I was taking a class in automata theory, and during one particular lecture, the instructor was having quite a bit of trouble finishing a proof. One of the students (call him Kurt; I don't remember his name) was repeatedly making corrections and giving helpful hints whenever the instructor got stuck. Finally, the instructor got so flustered that he handed Kurt the chalk and said: "Why don't *you* finish the proof!"

So Kurt took up the chalk, and continued with the proof. And he not only got it all right, he was an absolute model of confidence and clarity! He finished the proof with a flourish and a "QED," and rather than dealing with questions, or turning the chalk back over to the instructor, he began to tell a joke.

And not just any joke, but the old one about the Famous Scientist and his Chauffeur, who had heard the Scientist's lecture so many times that one evening they decide to switch, as a prank. In the joke, the Chauffeur gives the lecture flawlessly, but afterwards there is a question from the audience. Rather than try to answer it, he turns the chalk over to the Scientist, and says, "Sir, that question is so simple that even my Chauffeur can answer it!"

As Kurt delivered this punch line, he handed the chalk back to the instructor, and sat down. The instructor stared at the chalk in his hand for a moment, and then simply dismissed class for the day.

Howard Motteler (motteler@umbc.edu)

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