What is "church"? What makes the church one? While these questions may seem innocuous, church has become conflicted territory recently, with internal factions, external pressures, and ecumenical turmoil all calling for a more positive, studier, more resilient notion of Christian community. Wengert approaches the questions as a Reformation historian. He shows how the New Testament notion of "marks" of the church was taken up by Luther and developed by Melanchthon not as descriptive tag but as a criterion for authenticity in Christian community. Lathrop, the liturgical theologian, shows...