The Curia called on Luther to appear in Rome to answer for his unorthodox doctrines, threatening excommunication should he fail to do so. Luther preferred to have his case heard by German authorities. In October 1518 he participated in a series of interviews with Cardinal Cajetan, the pope’s personal representative, in Augsburg. The two sides failed to bridge their differences. As Luther gradually rejected important concepts of the Church, his teachings were condemned and he was ordered to recant. He was described as the “new Porphyry,” the philosopher whose work was banned by many Roman emperors. In January 1521 Luther was officially excommunicated.