In the long and unresolved drama of nuclear diplomacy, the United States and Iran have once again chosen conversation over silence. Secretary of State Marco Rubio announced this week that American negotiators have resumed talks with Tehran over its nuclear program, though he was careful to note that no common ground has yet been found. The reopening of channels suggests both sides have concluded that the cost of disengagement outweighs the discomfort of the table — a calculation that is itself a form of progress, however fragile.