Nearly 200 years before Eusebius was born, Luke announced his intention to "write an orderly account" of events related to Jesus Christ, based on careful investigation of "everything from the beginning" (see Luke 1:1-4). With this project, encompassing Luke and Acts, the physician established himself as the earliest church historian—in some eyes, anyway.

The Lucan books were considered reliable history almost universally before the nineteenth century. Then an influential school of thought centered at Tübingen University, Germany, attacked on several fronts: Luke's reports of miracles, his obvious theological aims, the suspicious similarity in voice and ideas among the author and everyone he quotes. A cadre composed mostly of British scholars fought back, and more recent investigations into the contours of ancient historiography have shown Luke to be more trustworthy than many of his contemporaries. Still, the place of his works in the biblical canon makes comparison with other historical works difficult.

First-century Jewish historian Josephus invites more comparisons with Eusebius: both befriended Roman emperors, both made broad use of sources no longer available, and, by modern tastes, both betray too much bias. Yet both are indispensible as reporters on their eras and traditions, because they give us information recorded by no one else.

Because Josephus switched to the Roman side as the Jewish revolt collapsed, Jews considered him a traitor. Christians, however, latched onto his work as independent corroboration of people, places, and events in their own tradition. Josephus's reports of the intertestamental and New Testament periods have earned his books a place beside the Bible on many Christians' shelves. Even so, it's a stretch to consider him an early church historian, because he hardly discussed the nascent church and mentioned Jesus, rather vaguely, only twice.