Although provoked by the indulgences peddled by Johannes Tetzel, the very first proposition which Luther offered for public debate in his Ninety Five Theses put the axe to the root of the tree of medieval theology: "When our Lord and Master, Jesus Christ, said 'Repent,' he meant that the entire life of believers should be one of repentance." From Erasmus' Greek New Testament, Luther had come to realize that the Vulgate's rendering of Matthew 4:17 by penitentiam agite ("do penance") completely misinterpreted Jesus' meaning. The gospel called not for an act of penance but for a radical change of mind-set...