Counterintelligence 101

From Peter Ustinov’s Romanoff and Juliet:

In the play Ustinov, as the Prime Minister of a small, neutral country squeezed between the giants of East and West, calls on the American ambassador and learns that the Americans know about a secret Soviet maneuver in the contest to dominate his country. After a bit of reflection the Prime Minister- crossing the stage- calls on the Soviet Ambassador. After some preliminaries he says to the Soviet Ambassador, “They know.” The Soviet Ambassador replies calmly, “We know they know.” Back to the American ambassador goes Ustinov, “”They know you know,” he says conspiratorially. The American Ambassador smiles confidently. “We know they know we know,” he answers. Ustinov returns to the Soviet Ambassador. “They know you know they know,” he says. To this the Soviet Ambassador replies, triumphantly, “We know they know we know they know.” Once again the Prime Minister calls on the American Ambassador. ” They know you know they know you know,” he says, weary and curious at the same time. The American Ambassador repeats it after him, counting on his fingers. “WHAT?!?” he suddenly cries in horror.