After his return from Rome, Luther received at the University of Wittenberg the degree of Doctor of Divinity. Now he was at liberty to devote himself, as never before, to the Scriptures that he loved. He had taken a solemn vow to study carefully and to preach with fidelity the word of God, not the sayings and doctrines of the popes, all the days of his life. He was no longer the mere monk or professor, but the authorized herald of the Bible. He had been called as a shepherd to feed the flock of God, that were hungering and thirsting for the truth. He firmly declared that Christians should receive no other doctrines than those which rest on the authority of the Sacred Scriptures. These words struck at the very foundation of papal supremacy. They contained the vital principle of the Reformation. Luther saw the danger of exalting human theories above the word of God. He fearlessly attacked the speculative infidelity of the schoolmen, and opposed the philosophy and theology which had so long held a controlling influence upon the people. He denounced such studies as not only worthless but pernicious, and sought to turn the minds of his hearers from the sophistries of philosophers and theologians to the eternal truths set forth by prophets and apostles. Precious was the message which he bore to the eager crowds that hung upon his words. Never before had such teachings fallen upon their ears. The glad tidings of a Saviour’s love, the assurance of pardon and peace through His atoning blood, rejoiced their hearts, and inspired within them an immortal hope. At Wittenberg a light was kindled whose rays should extend to the uttermost parts of the earth, and which was to increase in brightness to the close of time. But light and darkness cannot harmonize. Between truth and error there is an irrepressible conflict. To uphold and defend the one is to attack and overthrow the other. Our Saviour Himself declared, “I came not to send peace, but a sword,”(166) Said Luther, a few years after the opening of the Reformation: “God does not guide me, He pushes me forward, He carries me away. I am not master of myself. I desire to live in repose; but I am thrown into the midst of tumults and revolutions.”(167) He was now about to be urged into the contest.