VATICAN CITY - Fifty years ago this October, Blessed John XXIII and more than 2,500 bishops and heads of religious orders from around the world gathered in St. Peter's Basilica for the opening session of the Second Vatican Council.

Over the following three years, Vatican II would issue 16 major "pronouncements" on such fundamental questions as the authority of the church's hierarchy, the interpretation of Scripture, and the proper roles of clergy and laity. Those documents, and the deliberations that produced them, have transformed how the Catholic Church understands and presents itself within the context of modern secular culture and society.