When the Schmalkaldic League was defeated at the Battle of M hlberg and the Elector Johann Frederick was captured, the Lutheran Reformation's future seemed precarious at best. In order to avoid persecution or further hardship, some theologians were willing to assent to compromise formulas intended to placate the Roman Catholic emperor and princes. A few others, however, especially those gathered in Magdeburg, a city under siege, refused to do so. With Matthias Flacius, they held that "in the situation of confession and incitement to sin, nothing is an adiaphoron." This book includes translations of four of the important works Flacius wrote to buoy his fellow believers in their resistance and to explain what he and his coreligionists considered to be the proper biblical teaching regarding adiaphora.