Again was Albert sent back to Cologne, and Thomas was made his assistant professor. He at once attracted attention, was ordained priest, and became as famous for his sermons as for his lectures. After four years at Cologne Thomas was ordered back to Paris, travelling on foot, and begging his way, yet stopping to preach in the large cities. He was still magister and Albert professor, but had greatly distinguished himself by his lectures. His appearance at this time was marked. His body was tall and massive, but spare and lean from fasting and labor. His eyes were bright, but their expression was most modest. His face was oblong, his complexion sallow; his forehead depressed, his head large, his person erect. His first great work was a commentary of about twelve hundred pages on the "Book of Sentences," in the Parma edition, which was received with great admiration for its logical precision, and its opposition to the rationalistic tendencies of the times. In it are discussed all the great theological questions treated by Saint Augustine,--God, Christ, the Holy Spirit, grace, predestination, faith, free-will, Providence, and the like,--blended with metaphysical discussions on the soul, the existence of evil, the nature of angels, and other subjects which interested the Middle Ages. Such was his fame and dialectical skill that he was taken away from his teachings and sent to Rome to defend his Order and the cause of orthodoxy against the slanders of William of Saint Amour, an aristocratic doctor, who hated the Mendicant Friars and their wandering and begging habits. William had written a book called "Perils," in which he exposed the dangers to be apprehended from the new order of monks, in which he proved himself a true prophet, for ultimately the Mendicant Friars became subjects of ridicule and reproach. But the Pope came to the rescue of his best supporters. On the return of Thomas to Paris he was made doctor of theology, at the same time with Bonaventura the Franciscan, called "the seraphic doctor," between whom and Thomas were intimate ties of friendship. He had now reached the highest honor that the university could bestow, which was conferred with such extraordinary ceremony that it would seem to have been a great event in Paris at that time.