In bed that night I invented a special drain that would be underneath every pillow in New York, and would connect to the reservoir. Whenever people cried themselves to sleep, the tears would all go to the same place.... And when something really terrible happened—like a nuclear bomb, or at least a biological weapons attack—an extremely loud siren would go off, telling everyone to get to Central Park to put sandbags around the reservoir. What assumption does the narrator make in this excerpt?