The Apostolic Fathers are integral to understanding Christianity between the time of the apostles and the First Ecumenical Council in 325. This trio consists of St. Clement of Rome, St. Ignatius of Antioch, and St. Polycarp of Smyrna. They were the foremost leaders of the Early Church, and consisted of people who personally knew and were taught by the Apostles. The last of the books of the New Testament, the Book of Revelation, is believed to have been written in the late 1st century or early 2nd century by the longest-living disciple of Christ, St. John the Theologian. This dating means that many of the writings of the Apostolic Fathers were written immediately after the books of the New Testament or in the case of I Clement even contemporaneous to them or preceding them. Thus, they are often quoted as witnesses to the continuity between the Christianity practiced by the apostles under persecution, and the Christianity practiced by the imperial church since the Edict of Thessalonica in 380.

The corpus consists of the single Epistle of Clement to the Corinthians, the 7 Epistles of Ignatius, and the Epistle of Polycarp to the Philipians, along with the accounts of the martyrdoms of St. Ignatius and Polycarp. The importance of these texts cannot be understated. At one point in the Corinthian Christian community 1 Clement was even read in churches even into the 4th century and hence at least locally was considered “canon”. Among the themes that are common to each of the texts are the emphasis on fidelity to the faith and to church authority as established by the apostles and their successors, the glorification of martyrdom (especially in the case of St. Ignatius), and finally the emergence of the hierarchies of the church (bishop, priest and deacon).