St Cyprian, third-century bishop of Carthage, developed a theory of church unity almost universally accepted up to the European Reformation: to be a member of the body of Christ you needed to be in communion with a priest who was in communion with a bishop who in turn was incommunion with all other bishops in the world. But, how could you discern who was a legitimate bishop? And, on what kind of issue would it be right to break off communion? Additionally, could self-authenticating ministries, like those of martyrs and confessors who had suffered for the faith, supersede this order? Finally, did the Church need, and in what form, a universal bishop who could guarantee the integrity of the network of bishops? From back cover.