St. Augustine, who had led a free life as a teacher of rhetoric in Carthage and Rome, came in his later years to believe, as he struggled to overcome his youthful temptations, that sexual desire was the most devilish of man's enemies and the chief sign of his degradation. He could imagine no such unruly urgence in man's perfect estate, when Adam and Eve still dwelt in Paradise. But with man's fall sexual desire appeared as the sign and seal of human debasement. This theory is poignantly set forth in Augustine's _City of God_. He furnished therein a philosophy for the monks, and doubtless his fourteenth book was well thumbed by those who were wont to ponder somewhat wistfully on one of the sins they had fled the world to escape. Christian monasticism was spreading in western Europe in Augustine's time, and the monkist vows included "chastity". There followed a long struggle to force the whole priesthood to adopt a celibate life, and this finally succeeded so far as repeated decrees of the Church could effect it. Marriage was proper for the laity, but both the monastic and secular clergy aspired to a superior holiness which should banish all thoughts of fervent earthly love. Thus a highly unnatural life was accepted by men and women of the most varied temperament and often with slight success. The result of Augustine's theories and of the efforts to frustrate one of man's most vehement impulses was to give sex a conscious importance it had never possessed before. The devil was thrust out of the door only to come in at all the windows. In due time the Protestant sects abolished monasteries, and the Catholic countries later followed their example. The Protestant clergy were permitted to marry, and the old asceticism has visibly declined. But it has done much to determine our whole attitude toward sex, and there is no class of questions still so difficult to discuss with full honesty or to deal with critically and with an open mind as those relating to the intimate relations of men and women.