From the late 1520s, another dimension developed in the task of defending Luther's cause. The doctrinal rift with the Zwinglians and the continuing threat of civil disobedience showed up the necessity to clarify and delineate Luther's cause ever more sharply. As Melanchthon grappled with these problems, he continued his educational reforms at Wittenberg. He also began working on natural philosophy from the early 1530s. In this chapter I shall discuss Melanchthon's first natural philosophy textbook, the Commentarius de anima, which closely reflected the issues of his time.

DEFENDING LUTHER'S CAUSE

In the autumn of 1529 a conference was held at Marburg to resolve doctrinal differences among the Evangelicals concerning the Lord's Supper. This conference was called by Philip of Hesse whose ambition was to form a political alliance among the Evangelical Swiss, the southern German cities and upper Germany, and thus challenge the house of Habsburg. Doctrinal differences between Zwingli and Luther had to be resolved in order to clear the way for such an Evangelical political alliance. Zwingli and Oecolampadius attended from Zurich; Jacob Sturm, Caspar Hedio, Martin Bucer from Strasburg; Luther, Melanchthon and Justus Jonas from Wittenberg; and several others such as Myconius, Gruciger and Osiander convened at Marburg. The conference took place but no agreement was reached on the interpretation of the Lord's Supper. Luther adhered to the real presence of the body and blood of Christ while Zwingli advocated a ‘commemorative’ interpretation of the Eucharist.