Gregory enjoyed an unrivaled reputation during the Middle Ages as a writer. He is reckoned with Augustine, Ambrose, and Jerome as one of the four great Latin "fathers" of the Church. His works show, however, how much less cultivated his period was than that of his predecessors. His most popular book was his _Dialogues_, a collection of accounts of miracles and popular legends. It is hard to believe that it could have been composed by the greatest man of the time and that it was designed for adults. In his commentary on Job, Gregory warns the reader that he need not be surprised to find mistakes in grammar, since in dealing with so high a theme a writer should not stop to make sure whether his cases and tenses are right.[30] [Illustration: The Castle San Angelo, formerly the Tomb of the Emperor Hadrian] [Sidenote: Gregory as a statesman.] Gregory's letters show clearly what the papacy was coming to mean for Europe when in the hands of a really great man. While he assumed the humble title of "Servant of the servants of God," which the popes still use, Gregory was a statesman whose influence extended far and wide. It devolved upon him to govern the city of Rome,--as it did upon his successors down to the year 1870,--for the eastern emperor's control had become merely nominal. He had also to keep the Lombards out of central Italy, which they failed to conquer largely on account of the valiant defense of the popes. These duties were functions of the civil power, and in assuming them Gregory may be said to have founded the temporal power of the popes. [Sidenote: Gregory's missionary undertakings.] Beyond the borders of Italy, Gregory was in constant communication with the emperor, with the rulers of Austrasia, Neustria, and Burgundy. Everywhere he used his influence to have good clergymen chosen as bishops, and everywhere he watched over the interests of the monasteries. But his chief importance in the history of the papacy is attributable to the missionary enterprises which he undertook, through which the great countries which were one day to be called England, France, and Germany were brought under the sway of the Roman Church and its head, the pope. Gregory was, as we have seen, an enthusiastic monk, and he naturally relied chiefly upon the monks in his great work of converting the heathen. Consequently, before considering his missionary achievements, we must glance at the origin and character of the monks, who are so conspicuous throughout the Middle Ages.