Question: "Who were the early church fathers?"
Answer: The early church fathers fall into three basic categories, Apostolic Fathers, Ante-Nicene Church Fathers and Post-Nicene Church Fathers. The Apostolic Church Fathers were the ones like Clement of Rome who were contemporary with the Apostles and were probably taught by them, carrying on the tradition and teaching of the Apostles themselves. Linus, mentioned in 2 Timothy 4:21, became the bishop of Rome after Peter was martyred, and Clement took over from Linus. Both Linus and Clement of Rome, therefore, are considered Apostolic Fathers. However, there appear to be no writings of Linus that have survived, while many of the writings of Clement of Rome survived. The actual Apostolic Fathers who were taught by the apostles would have largely all passed from the scene by the beginnings of the second century, except for those few that might have been disciples of John the Apostle, such as Polycarp. John died in Ephesus around 99 A. D.
The Ante-Nicene Fathers were those who were after the Apostolic Fathers and before the Council of Nicea in 325 A. D. Such luminaries as Iraenus, Ignatius, and Justin Martyr are Ante-Nicene Fathers.
After the Council of Nicea in 325 A. D. arose the Church Fathers who are considered Post-Nicene. Here, there are such noted men as Augustine, bishop of Hippo, who is often called the father of the Church (Roman Catholic Church) because of his great work in Church doctrine; Chrysostom, the golden-mouthed, for his excellent oratorical skills; and Eusebius, who wrote a history of the Church from the birth of Jesus to 324 A. D., one year before the Council of Nicea. He is included in the Post-Nicea era since he did not write his history until after the Council of Nicea was held. Other Post-Nicene Fathers were Jerome, who translated the Greek New Testament into the Latin Vulgate; and Ambrose, who was largely responsible for the emperor Constantine being converted to Christianity.
So, what did the Early Church Fathers believe? The Apostolic Fathers were very concerned about the proclamation of the Gospel being just as the Apostles themselves proclaimed it. They were not interested in formulating theological doctrine, for the gospel they had learned from the Apostles was quite sufficient for them as far as orthodoxy was concerned. The Apostolic Fathers were as zealous as the Apostles themselves in rooting out and exposing any false doctrine that began to crop up here and there. The orthodoxy of the message was preserved by the Apostolic Fathers' desire to stay as true to the gospel taught to them by the Apostles as they possibly could.
The Ante-Nicene Fathers also tried to stay as true to the Gospel they had been taught as possible, but they had an additional worry not present with the Apostolic Fathers. Now there were several spurious writings claiming to have the same weight as established writings from the likes of Paul, Peter, and Luke. The reason for these spurious documents was quite evident, for if the Body of Christ could be persuaded that a spurious document was the same as a document that was seen as genuine, then the spurious document would be seen as genuine also. So the Ante-Nicene Fathers begin to spend a lot of their time defending the Christian faith from false doctrine, and this led to the beginnings of forming church doctrine.
The Post-Nicene Fathers carried out the mission of the defense of the Gospel against all kinds of heresies and false doctrines, so more and more the Post-Nicene Fathers began to be more interested in the defense of the gospel and less interested in the transmitting of the gospel in a true and pure form, which was the hallmark of the Apostolic Fathers. By the time of Augustine, the father of Catholic doctrine, the need to defend against heresies and false doctrines had reached the point that the true doctrine of the Body of Christ was pretty much settled on. This was the age of the theologian who would discuss arcane topics to death, such as “how many angels can dance on the head of a pin.”