There have been twenty-one universal gatherings--ecumenical councils--of the Catholic Church. The first opened in 325, the last closed in 1965, and the names of many ring out in the history of the church: Nicea, Chalcedon, Trent, Vatican II. Though centuries separate the councils, each occurred when the church faced serious crises, sometimes with doctrinal matters, sometimes with moral or even political matters, and sometimes with discerning the...