Eusebius of Caesarea (c. 260–c. 340) is known as the “father of church history.” He was the first to write a “comprehensive” history of the early church. Eusebius of Caesarea is to be distinguished from his contemporary Eusebius of Nicomedia.
Eusebius of Caesarea was born in Palestine, and little if anything is known of his early life and conversion. In Palestine, Eusebius came under the influence of Pamphilus, who was a student of Origen. Pamphilus had amassed a large library of Origen’s writings, copies of Scripture, and commentaries—truly one of the great ancient Christian libraries. It seems that Eusebius fled the persecution of Christians in Palestine and eventually made his way to Egypt where he witnessed Christian martyrdom firsthand. He was also imprisoned for a short time. In 313 or 314, Eusebius was made bishop of Caesarea in his native Palestine.
The theology of Eusebius is problematic. He was somewhat sympathetic to the Arian position, while not fully embracing it himself. He was present at the Council of Nicaea and signed the Nicene Creed (perhaps being pressured to do so by Emperor Constantine), but he was never in full support of it as later writings made clear. Eusebius felt that the condemnation of Arius was too strong.
Eusebius of Caesarea wrote several major works. In Preparation for the Gospel (15 books), he refutes paganism, using extensive quotes from pagan authors. In Demonstration of the Gospel (20 books), he examines how Christ fulfilled Old Testament prophecies. In his most famous and perhaps most important work, Ecclesiastical History (10 books), Eusebius provides a history of the church from apostolic times through the death of Constantine.
Ecclesiastical History is important for a number of reasons. It uses extensive quotations from primary sources that would be lost to us otherwise. It records the succession of bishops and teachers in major sees from apostolic times. It highlights the battles against heresy and the internal struggle to understand and formulate a biblical doctrine of the Trinity. It gives details on persecutions and martyrdoms. It preserves traditions about the New Testament writers and gives details regarding the canon. By the time of Eusebius, most of the current New Testament was accepted as canonical. James, Hebrews, 2 Peter, 2 and 3 John, and Revelation were the only books not fully accepted. Finally, Eusebius provides an account of the conversion of Constantine, the details of which he received from Constantine himself, the two having become close friends.
Eusebius seems to have taken his historical sources at face value and is not considered a critical historian. He also seems to have been somewhat blinded in admiration for Constantine. However, this appreciation for a Christian emperor may be understandable coming from one who had personally witnessed persecution and martyrdom. With the Edict of Constantine, it truly seemed that a new world was at hand and that the church was going to triumph in the secular realm.