The really distinctive achievement of Paul, however, does not consist in the mere geographical extension of the frontiers of the Church, important as that work was; it lies in a totally different sphere--in the hidden realm of thought.[6] What was really standing in the way of the Gentile mission was not the physical barriers presented by sea and mountain, it was rather the great barrier of religious principle. Particularism was written plain upon the pages of the Old Testament; in emphatic language the Scriptures imposed upon the true Israelite the duty of separateness from the Gentile world. Gentiles might indeed be brought in, but only when they acknowledged the prerogatives of Israel and united themselves with the Jewish nation. If premonitions of a different doctrine were to be found, they were couched in the mysterious language of prophecy; what seemed to be fundamental for the present was the doctrine of the special covenant between Jehovah and His chosen people. [6] For what follows, compare the article cited in _Biblical and Theological Studies_, pp. 555-557. This particularism of the Old Testament might have been overcome by practical considerations, especially by the consideration that since as a matter of fact the Gentiles would never accept circumcision and submit to the Law the only way to carry on the broader work was quietly to keep the more burdensome requirements of the Law in abeyance. This method would have been the method of "liberalism." And it would have been utterly futile. It would have meant an irreparable injury to the religious conscience; it would have sacrificed the good conscience of the missionary and the authoritativeness of his proclamation. Liberalism would never have conquered the world. Fortunately liberalism was not the method of Paul. Paul was not a practical Christian who regarded life as superior to doctrine, and practice as superior to principle. On the contrary, he overcame the principle of Jewish particularism in the only way in which it could be overcome; he overcame principle by principle. It was not Paul the practical missionary, but Paul the theologian, who was the real apostle to the Gentiles.