Eusebius of Caesarea

The Ecclesiastical History is unusual for an ancient work in that it argues by producing evidence. Eusebius quotes his sources at length, names them, and distinguishes what he has read from what he has been told, which was not the normal practice of ancient historians and is the reason his book is indispensable. Whole authors survive only inside it. Papias on the origins of the gospels, Hegesippus on the Jerusalem church, Julius Africanus on chronology, letters of Dionysius of Alexandria and of the churches of Lyons and Vienne about their martyrs: in each case the original is lost and the excerpt is what remains.

He also had to invent the shape of the thing. No one had written the history of a religious community as a continuous institution before, so he built it out of four running threads, the succession of bishops in the great sees, the appearance of heresies, the sufferings of the martyrs, and the fate of the Jewish people, and later church history inherited that frame more or less intact. The companion works do similar structural work. The Chronicle sets biblical, Greek, Persian and Roman dates in parallel columns so that events in one tradition can be located in another. The system of sections and tables he devised for the four gospels, which lets a reader find the parallel passages, is still printed in critical editions of the Greek New Testament.

Eusebius came to the council of 325 from the wrong side of the argument. He had been in communion with Arius, had written on his behalf, and had been provisionally censured at Antioch shortly before. At Nicaea he submitted a creed of his own, then signed the one the council produced, and afterwards wrote to his congregation at Caesarea explaining in what sense he understood the word of one substance, which is not the letter of a man who has been persuaded. He continued to act against Athanasius in the years that followed. For the tradition that eventually settled on the Nicene formula, that record was disqualifying, and the man who preserved more of the early church than anyone else is commemorated in the Eastern churches but is not a saint in the Western calendars.

His other legacy is political. The Life of Constantine is a panegyric, and has to be read as one, but the oration he delivered for the emperor thirtieth anniversary is a piece of theology with consequences: one God, one divine Word, one emperor who rules as the image of that Word and whose empire mirrors the heavenly monarchy. That argument gave the Christian empire a doctrine of itself, and Byzantine political thought worked with it, and against it, for the next eleven hundred years.