other · 324 · Caesarea Maritima
He had the library Pamphilus built at Caesarea, and he used it the way nobody had used a library before: the Ecclesiastical History is built out of quotation. Hegesippus, Papias, Dionysius of Corinth, the letter of the churches of Lyons and Vienne, Irenaeus on the succession at Rome, the correspondence of Cyprian's generation — for a great many of these he is the only reason a word survives, and this dataset cites him more than any other source for exactly that reason. He states his own programme at the start: the successions from the apostles, those who governed and presided in the most famous churches, those who preached the word in writing, the heresies, what befell the Jews, the persecutions, and the martyrdoms. That list is very close to a description of this dataset. He also has his faults and they are on the record here too — he is a partisan of Constantine, he is coy where he is embarrassed, and he was on the wrong side of Nicaea for a while. The book is still the foundation.
To write down, before the witnesses and the documents were lost, the succession of bishops in the great sees, the writers, the heresies, and what had happened to the martyrs.
The genre of church history, and the survival of most of what anyone knows about the first three centuries.