American mythology loves nothing more than the reluctant hero: the man -- it is usually a man -- whose natural talents have destined him for more than obliging obscurity. George Washington, we are told, was a leader who would have preferred to have been a farmer. Thomas Jefferson, a writer. Martin Luther King, Jr., a preacher. These men were roused from lives of perfunctory achievement, our legends have it, not because they chose their own exceptionalism, but because we, the people, chose it for them. We -- seeing greatness in them that they were too humble to observe themselves -- conferred on them uncommon paths. Historical circumstance became its own call of duty, and the logic of democracy proved itself through the answer.NeilArmstrong was a hero of this stripe: constitutionally humble, circumstantially noble. Nearly every obituary written for him has made a point of emphasizing his sense of privacy, his sense of humility, his sense of the ironic ordinary.And yet every aspect ofArmstrong’s life made clear: On that day in 1969, he acted on our behalf, out of a sense of mission that was communal rather than personal. The reluctant hero is also the self-sacrificing hero.