If, during the second century, the church appeared not to be fully conscious of the theological task facing her, at the same time she was laying a foundation for the more specifically doctrinal development that lay ahead of her. The task of apologists like Theophilus and Justin, Athenagoras and Aristides and the rest, was to enter into dialogue with pagan detractors of the faith, a philosophical rather than a strictly theological exercise. The task of pastors like Ignatius, Irenaeus, and to a lesser extent Melito, was to proclaim the gospel to the faithful and to protect them from gnostic perversions of the faith. By the end of the century St John's Gospel had established its position within the church; it gave to the church a terminology which had points of contact with pagan thought and at the same time placed in her hand a weapon with which to defeat the syncretising forces of gnosticism.

This double stimulus—the necessity to defend her gospel on two points, against pagan attack from without and gnostic subversion from within—continued during the third century. In the west, Hippolytus and Tertullian continued the battle against gnosticism so ably begun by Irenaeus, using the same weapons of scripture and appeal to the traditional faith of the church, based on scripture and handed down from apostolic times, enshrined in catechetical instruction and most succinctly expressed in the early baptismal creeds. At the same time Tertullian continued the apologetic task in treatises like his Apology and de Testimonio Animmae.