We possess very few written remnants of the time immediately succeeding the Apostles. The writers are St. Clement of Rome, St. Barnabas, Hermas, St. Ignatius of Antioch, St. Polycarp, Papias, and the writer of the letter to Diognetus. With the exception of the "Pastor," these are all in the form of letters, conveying strong feelings expressed in few words, short and touching exhortations, simple narratives of joys and sorrows. These first Christians were anything but literary; they were only conscious of possessing a divine truth which had incomparable value above all earthly things. Nevertheless it deserves to be remarked, that short as these writings are, we have in them the first outlines of all future learned teaching.[173] In the letter to Diognetus we have a sketch of the course which Christian apology against heathens afterwards took; in the letters of St. Ignatius, the first features of the Church's defence against heretics; in the letter of Barnabas, an approach to speculative theology; in the "Pastor," the first attempt at a Christian science of morals; in the letter of Pope St. Clement, the first development of the government which afterwards produced the Canon Law; and in the Acts of St. Ignatius' martyrdom, the earliest historical production. In these, as it were, infantine movements of His first disciples, the Divine Child was manifesting the future conquests which He would achieve in leading His people through the whole range of the divine science. In the second century the Church vastly increased in the number of her faithful and in her influence; at the same time she was exposed to much severer attacks from within and without. Through the whole century the false Gnosis afflicted her. The Greek and the Oriental philosophy had fully detected the presence of a great enemy, and fought against her with all the arms of learning, the brilliance of Eastern imagination, the fire of religious zeal. It is said that in the first fifteen hundred years no sect has pushed the Church more hardly than Gnosticism, which through the brilliant talent of its leaders in Alexandria, Antioch, Edessa, and other great cities gained many adherents. The attacks from the heathen and the defacements which Christian doctrine received through heretics formed thus the strongest challenge to Christians to defend themselves with the arms of learning and science on their own side.