Carl E. Braaten. Principles of Lutheran Theology 2nd edition. Minneapolis: Fortress Press, 2007 Chapter 3 “The Ecumenical Principle” pp. 53-72
Braaten now turns his attention to the unity of the Church, repeating many times his affirmation of “one holy catholic and apostolic church.” The church is to be one body. How then do we deal with the many groups which claim autonomy and at least some degree of exclusivity? On p. 53 Braaten says that Luther followed Augustine in affirming both a corpus mixtum and some sort of a “true” church, all the believers. Lutherans also accept the idea of a special, ordained clergy as well as a priesthood of all believers. The ministry, and even the very existence, of the Church is based on Word and Sacraments. This, says Braaten, should pull all Christians together, providing common ground. He observes that throughout history Christians have found themselves unified or divided based on faithfulness to Word and Sacrament, as well as four attributes: unity, holiness, catholicity, and apostolicity. He discusses those four attributes in detail, demonstrating in each case that unity can be found. If we took doctrine seriously and pursued those six concepts, we could find unity in the Church. There would remain room for variants in different places and among different groups. But there would be unity.