"Professor Eddington," Silberstein declared, "you must be one of three persons in the world who understands general relativity." When Eddington demurred, Silberstein continued: "Don't be modest, Eddington."
"On the contrary," Eddington replied. "I am trying to think who the third person is!"
[Eddington was once asked how many people could really understand his theory of the expanding universe. He paused for a moment before replying: "Perhaps seven."]