I was in the Speer library at Princeton Seminary in the summer of 1976 and I was looking for the Loeb edition of Eusebius’ Church history. The card catalog said it was on the shelf, but in fact it was not. I notified the dower old librarian of the fact, and she went to look for herself, not trusting a mere student like me. She came back and confirmed it had gone missing. I decided she hadn’t likely smiled in a while so I quipped ‘Well I guess it’s a case of now Eusebius and now you don’t’!’ This produced a quiet cackled and a smile almost cracked her serious face. But alas, I had to go look elsewhere for Eusebius. One of the real problems with Eusebius is just when you think you have gotten him clearly in view, he slips from your sight line. Now you see him, and now you don’t.
Eusebius is rightly one of the most beloved and belabored of church historians, and in this post I do not intend to summarize the debate but rather to make a few suggestions on how he should be read. Eusebius, as his book Proof of the Gospel, shows is an apologist and in his church history he is an apologist for Constantine and his policies, among other things. His work must be read as an example of rhetorical history writing, tending towards epideictic rhetoric when he waxes eloquent about Constantine, and as such his work must be read critically and carefully. It cannot be taken at face-value, though it must be taken quite seriously, as Eusebius, despite his hyperbole, is not simply making things up as he goes along, and frequently, when he can be checked, he appears to be basically historically reliable when it comes to the facts of the matter or when he is quoting sources.
The second cautionary word about Eusebius is that he is not pretending to be an unbiased reporter. As I said, he is an apologete and he pursues a particular line of argument. This again should not lead to cynicism about what he says, but it should lead to caution as one reads his writings. Constantine was definitely not without his flaws and foibles which Eusebius tends to gloss over. When he is not busy defending Constantine however, Eusebius tells us a great deal we would not otherwise know about early Christian history, and where we can check what he says, it appears to be accurately cited, especially when it is not about a matter he has a bias about. But this leads to the third point.
Eusebius definitely does have some theological biases as well. For example, he does not like pre-millenial eschatology, and offers some unfair critiques of folks like Papias of Hierapolis who affirmed, with many other early Christians, a non-Dispensational form of pre-millenialism. Bear these things in mind.