The Occasion of the Work. -- Luther did not impose himself as reformer upon the Church. In the course of a conscientious performance of the duties of his office, to which he had been regularly and divinely called, and without any urging on his part, he attained to this position by inward necessity. In 1515 he received his appointment as the standing substitute for the sickly city pastor, Simon Heinse, from the city council of Wittenberg.