Only months after Luther's death in 1546, a colleague, Caspar Cruciger, Sr., published his magnum opus, an 879-page commentary on the Gospel of John, In Evangelium Iohannis Apostoli Enarratio. Cruciger's Enarratio provides an excellent angle from which scholars may examine an important shift in Wittenberg's exegesis and theology during the crucial decade of the 1540s. To be sure, this work has few of the characteristics of other treatments of the fourth Gospel produced near the same time. The exposition of the four Gospels by Cologne's Franciscan theologian, von Konigstein, underwent far more printings. The works on John by Calvin and Bullinger have attracted more attention in our own day. However, when set into the context of continued sharp debate over ecclesiology, Cruciger's commentary on John provides a critical reshaping of Philip Melanchthon's exegetical method to meet the continuing challenge of defining the church in line with an emerging Lutheran orthodoxy and against Roman Catholicism. Unlike later Protestant commentaries, which often roll ponderously from one unrelated locus in theology to the next, Cruciger's work, though massive, focuses almost singlemindedly on the doctrine of the church. The commentary represents part of Wittenberg's response to failed discussions over the nature of the church and its authority which began in 1520, nearly halted in 1541 at the Colloquy of Regensburg which Cruciger attended, and collapsed with the outbreak of hostilities during the Smalcald War of 1547. It also demonstrates the farreaching effect of Philip Melanchthon's exegetical method in shaping that response among his own students.