The Judaizing party not only tried to inoculate the Church with Judaism, but strained every nerve to undermine the authority of St. Paul. They said that he had no authority to preach Christ unless it was derived through the Twelve, and they showed "letters of commendation" (Gal. ii. 12; 2 Cor. iii. 1), to the effect that they represented the first apostles and came to supply the defects of St. Paul's teaching. With these opponents he was in conflict during his third missionary journey, which began about August, A.D. 52. On this journey he revisited Galatia and Phrygia, made a long stay at Ephesus, and went to Macedonia and Greece. During this third missionary journey he wrote 1 and 2 Corinthians, Galatians, and Romans. It is hard to determine the exact order in which they were written, as Galatians may have been written before 1 Corinthians. These Epistles are the noblest work of St. Paul. The persistent efforts of his opponents compel him to defend both his principles and his character. Amid the perplexity of the time, his clear and clarifying mind formulated Christian doctrine so perfectly that he compels his readers to see what he sees. This group of Epistles is mainly devoted to _soteriology_, or the method by which God saves man. It contains abundant teaching about God's purpose of saving us, the use of the Jewish law, the struggle between our flesh and our spirit, the work of Jesus Christ in dying and rising for us, the work of the Holy Spirit, and the morals and worship of the Church. St. Paul's arguments are mainly addressed to believing Christians, whom he wishes to preserve from Jewish or heathen error. They are marked by the strongest light and shade. Nowhere does sin appear more awful, and the love of God to undeserving man appear more generous. At one moment the apostle writes as a logician, at another as a mystic. Now he is stern, and now he is pathetic. In compass, in variety, in depth, these four Epistles are great works of art, and all the greater {123} because the writer esteems his intellectual powers as nothing in comparison with the story of the Cross.