I’ve talked a bit lately about what Christians today might be able to learn from the early church. Let’s do that again.

Celsus was a second-century Greek philosopher who, around 175 A.D., wrote an extremely thorough critique of Christianity, which he believed to be a philosophical and moral abomination. Alas, no copies of it have survived. And yet we know in detail not just what Celsus argued but also the specific words in which he argued it. How?

Because 75 years later, when a Christian theologian named Origen wrote a book called Against Celsus, he quoted his opponent often and at great length — and in such a way that we can see that Celsus knew Jewish and Christian writings and history pretty thoroughly. That is, thanks to Origen’s scholarly integrity, it is possible for readers to follow the dispute and decide that Celsus got the better of it.

In short, Celsus was scrupulously fair to the person whose ideas he wanted desperately to refute. He did not take refuge in the kinds of phrases we see so often today, from Christian and non-Christian alike: “In other words, Celsus believes…” or “In effect, Celsus is saying….” Nor does he take up the evasive strategy of “some critics have claimed” — evasive, but tempting, because you can’t be accused of misreading someone when you won’t say who you’re responding to. Origen wasn’t trying to dunk on his enemies on social media. Instead, he said: (a) Here are Celsus’s words, (b) Here’s why I think he’s wrong.

A surprising large amount of the Christian theology and philosophy produced in the period between, say, Tertullian and Augustine was extremely vigorous: responsible but also bold and imaginative, and considerably more of all of that than the pagan thought of the period. Eric Osborn, in his book The Emergence of Christian Theology, claims that the power of Christian intellectual life was a kind of secret ingredient in the faith’s phenomenal growth throughout the third century. A word to the wise — and especially to the not-yet-wise.