“Very unlikely people, you know, will share confidences with each other if they think the other person understands. A prisoner who won’t tell a guard anything will thaw immediately if he’s put in a cell with another man in for the same crime. And doctors who would bite off their own tongues before showing indecision to a patient will tell another doctor about how little they know and how frightened they are. I’ve seen it happen many times. It’s how spies work.”