In 1589 he was summoned to Rome to take part in the great theological battle on grace. The task assigned to him was to prove the orthodoxy of Molina, which he did so effectively and with such consummate skill that both friend and foe awarded him the palm. But the battle was not over, for it was charged that isolated statements taken from Molina's book contradicted St. Augustine. Consequently all of St. Augustine's works had to be examined; a scrutiny which of course called for endless and crushing labor, but he set himself to the task so energetically that when the debates were resumed his health was shattered, and he was allowed to remain seated during the discussions. Thomas de Lemos was his antagonist at this stage. In the ninth session, Gregory's strength gave way and he fainted in his chair. His enemies said it was because the Pope had reproached him with tampering with St. Augustine's text, but as his holiness had decorated him with the title of "Doctor doctorum," the accusation must be put in the same category as the other which charged the Jesuits with poisoning Clement VIII so as to prevent him from condemning their doctrine. According to the "Biographie universelle," Denis Pétau, or Petavius, was one of the most distinguished savants of his time. He was born at Orléans, August 21, 1583, and there made his early studies. Later he went to Paris, and at the end of his philosophical course defended his thesis in Greek. He took no recreation, but haunted the Royal Library, and amused himself collecting ancient manuscripts. It was while making these researches, that he met the famous Casaubon, who urged him to prepare an edition of the works of Synesius. While engaged at this work, he was chosen for the chair of philosophy at Bourges, though he was then only nineteen years old. As soon as he was ordained to the priesthood, he was made canon of the cathedral of his native city. There he met Father Fronton du Duc and entered the Society. After his novitiate, he was sent to the University of Pont-à-Mousson for a course of theology. He then taught rhetoric at La Flèche, and from there went to Paris. His health gave way at this time, and he occupied himself in preparing some of the works which Casaubon had formerly advised him to publish. In 1621, he succeeded Fronton du Duc as professor of positive theology, and continued at the post for twenty-two years with ever increasing distinction.