This common opinion, moreover, was strongly reinforced by pedagogical needs. The sweep of the new religion and its gathering in converts from all sorts of curious moral highways and hedges had created a situation that taxed to the uttermost the powers of the Christian teachers. Multitudes of neophytes were constantly demanding instruction, and to teach each one of them how to apply Christ’s deeper principles to involved special problems seemed utterly impracticable; why engage in so intricate a task when a succinct Old Testament precept could settle the matter instantly? So catechetical moral training was usually given by means of short digests based on Old Testament laws, some of these digests being undoubtedly of Jewish origin.[11] But it is interesting to note that the most authoritative brief digest of Jewish morality—the Decalogue—does not appear as a whole in the Christian teaching.[12] In Gentile Christianity concrete rules were taken likewise from Greek ethical works, whose standard was usually high. Only the learned, of course, could appreciate the moral treatises of the great philosophers, but a long succession of teachers—chiefly Stoics—had devoted themselves to bringing an understanding of good conduct within the reach of all. Among other means, these teachers achieved their purpose by requiring their pupils to memorize short gnomic formulas, or—the ultimate extremity of simplification—bare lists of virtues to be imitated or vices to be avoided.[13] This last device was so convenient that even Greek-speaking Jews adopted it,[14] and Christians found it invaluable. In fact they did not hesitate to take ready-made lists from Stoic and other sources,[15] so giving Greek ethical concepts an unnoticed but authoritative entrance into Christianity. Less formal but very real was the influence of established customs and conventions—on occasion, even superstitions—in contemporary life, whether Jewish or Gentile. St Paul, for instance, in 1 Corinthians 11. 4 holds it to be obvious that men should pray with their heads uncovered, and this passage has influenced all subsequent Christian practice. Yet the ruling rests on nothing more profound than the religious habits of the particular Jews among whom St Paul was brought up; other Jews in his day believed that God should be approached only when the head was covered, and this came to be the accepted Jewish practice. If St Paul had lived elsewhere—or if he had been born somewhat later—the declaration in 1 Corinthians 11. 4 would have shocked him.