One day when the blessed Peter was making his way through the country about Milan he happened on two men sowing their fields, of whom one was a Catholic, the other a heretic. The Catholic before beginning his work called on God to help him, but the heretic invoked the devil, whom as the maker of the visible world he believed to have the government of the earth and its crops; and when they heard one another each condemned the other for the perversity of his faith. The blessed Peter who by the will of God was passing that way drew near. . . .’ The outcome is hardly in doubt: St Peter prophesied, and when in time the field of the Catholic bore a plentiful crop and the heretic’s none, the heretic was convinced by the miracle and became a Catholic. But St Peter was not always as confident as on that occasion. Another day he met a heretic who challenged him to a disputation. St Peter, unprepared, was momentarily overwhelmed by his subtleties and went into a church to pray; even there, before the Lady altar, he was visited by doubt and trepidation, and it required the voice of the Blessed Virgin herself to reassure him.