In the early 16th century , movements were begun by two theologians , Martin Luther and Ulrich Zwingli , that aimed to reform the Church ; these reformers are distinguished from previous ones in that they considered the root of corruptions to be doctrinal ( rather than simply a matter of moral weakness or lack of ecclesiastical discipline ) and thus they aimed to change contemporary doctrines to accord with what they perceived to be the `` true gospel '' . In the early 16th century , movements were begun by two theologians , Martin Luther and Huldrych Zwingli , that aimed to reform the Church ; these reformers are distinguished from previous ones in that they considered the root of corruptions to be doctrinal ( rather than simply a matter of moral weakness or lack of ecclesiastical discipline ) and thus they aimed to change contemporary doctrines to accord with what they perceived to be the `` true gospel . ''