Where did Jean Piaget fit in when, in 1929, he agreed to lead the young International Bureau of Education (IBE) in Geneva? How did a psychologist famous for studying children’s moral reasoning end up running the first intergovernmental organization built to secure peace through education? What tools from his own theories – reciprocity, self-government, the “ascent from the individual to the universal” – did he quietly bring into rooms full of ministers and diplomats? And what did it mean for one of his own students, decades later, to recognize his teacher’s fingerprints on every recommendation the IBE ever produced?