Enrico Ferni, the famous atomic physicist, was once giving a lecture on the principles of quantum physics to a lay audience. At the end, he was keen to know how his lecture had gone and whether it had been simple enough to be understood. He collared a student as he was leaving, and asked him.
The student, slightly embarrassed, is said to have replied, ‘Professor Ferni, to be honest, after our lecture, I’m confused. But I’m confused at a higher level’!
Many thanks to Paul who sent me this story on a card some years ago.