Book excerpt: There is today a dramatic reexamination of structure, authority, dogma -- indeed, every aspect of the life of the Church is held up to scrutiny. Welcoming this as a sign of vitality, Avery Dulles has carefully studied the writings of contemporary Protestant and Catholic ecclesiologists and sifted out six major approaches, or "models," through which the Church's character can be understood: as Institution, Mystical Communion, Sacrament, Herald, Servant, and, in a recent addition to the book, as Community of Disciples. A balanced theology, he concludes, must incorporate the major affirmations of each. "The method of models or types," observes Cardinal Dulles, "can have great value in helping people to get beyond the limitations of their own particular outlook and to enter into fruitful conversation with others... Such conversation is obviously essential if ecumenism is to get beyond its present impasses." This new edition includes a new Appendix and Preface by the author.