EUSEBIUS OF CAESAREA.

Eusebius of Caesarea (260/265-339/340), also known as Eusebius Pamphili, was a historian of Christianity. He became the bishop of Caesarea Maritima about 314 CE. He is regarded as an extremely learned Christian of his time.
The city port and the coastal city of Caesarea was described in detail by the 1st-century Roman Jewish historian Flavius Josephus. He describes tha harbor as being as large as the one at Piraeus, the major harbor of Athens. Remains of the principal buildings erected by Herod and the medieval town are still visible today, including the city walls, the castle and a Crusader cathedral and church. Caesarea grew rapidly, becoming the largest city in Judea. At its height, the port was one of the most impressive harbors of its time. It had been constructed on a coast that had no natural harbors and served as an important commercial harbor in antiquity, rivaling Cleopatra's harbor at Alexandria.
Little is known about the life of Eusebius. His surviving works probably only represent a small portion of his total output.
By the 3rd century, Caesarea had a population of about 100,000. Pompey gave control of the city to the gentiles during his command of the Eastern provinces in the 60s BC. The gentiles retained control of the city for the 3 centuries to follow. Gentile government was strengthened by the city's refoundation under Herod the Great (37-34 BC), when it had taken on the name of Augustus Caesar. In addition to the gentile settlers, Caesarea had large Jewish and Samaritan minorities. Eusebius was probably born into the Christian contingent of the city. Caesarea's Christian community had a history reaching back to apostolic times.
Through the activities of the theologian Origen (185-254 CE) and the school of his follower Pamphilus (later 3rd century-309), Caesarea became a center of Christian learning. Origen was largely responsible for the collection of usage information, or which churches were using gospels, regarding the texts which became the New Testament. Eusebius used the information passed on to him by Origen to create his list and Origen's list about what texts were accepted by the 3rd-century churches throughout the known world. Together with the books of Origen's patron Ambrosius, Origen's library formed the core of the collection that Pamphilus established. He had gathered Bibles from all parts of the world and maintained close contact with his students. Eusebius, in his history of the persecutions, alludes to the fact that many Christians martyrs lived together in Caesarea, under Pamphilus' protection.
Pamphilus began teaching Eusebius, who was then somewhere between 20 and 25 years old. Neither Panphilus nor Eusebius knew Origen personally. Pamphilus probably picked up Origenist ideas during his studies in Alexandria.
In the 290s, Eusebius began to work on his Magnum Opus, the Ecclesiatical History, a narrative history of the Church and Christian community from the Apostolic Age to Eusebius' own time, and completed the first edition of his work before 300 CE. At about the same time, Eusebius worked on his Chronicle, a universal calendar of events from the Creation to, again, Eusebius' own time.
Eusebius succeeded Agapius as Bishop of Caesarea soon after 313 CE and was called on by Arius who had been excommunicated by his bishop Alexander of Alexandria. An episcopal council in Caesarea pronounced Arius blameless. Eusebius, a learned man and famous author, enjoyed the favor of the Emperor Constantine. Because of this he was called to present the creed of his own church to the 318 attendees of the Council of Nicaea in 325 CE. However, the anti-Arian creed from Palestine prevailed becoming the basis for the Nicene Creed.
The theological views of Arius, that taught the subordination of the Son to the Father, continued to be a problem. Eustathius of Antioch strongly opposed the growing influence of Origen's theology as the root of Arianism. Eusebius was reproached by Eustathius for deviating from the Nicene faith. Eusebius prevailed and Eustathius was deposed at a synod in Antioch.
Eusebius remained in the Emperor Constantine's favor throughout this time and more than once was exonerated with the explicit approval of the Emperor. After Constantine's death (337 CE), Eusebius wrote the Life of Constantine, an important historical work. Eusebius died in 339 CE. Much like his birth, the exact date of Eusebius' death is unknown.
From a dogmatic point of view, Eusebius stands entirely upon the shoulders of Origen. Like Origen, he started from the fundamental thought of the absolute sovereignty of God. God is the cause of all beings. But He is not merely a cause; in Him everything good is included, from Him all life originates, and He is the source of all virtue. God sent Christ into the World that it may partake of the blessings included in the essence of God. Christ is God and is a ray of the eternal light.