Justin Martyr says that he was impressed in his study of the Old Testament, at the seriousness and contents of these writings, and became convinced that Jesus fulfilled these texts.

Galen recognized, with some considerable puzzlement it seems, that Christians exhibited the virtues that he associated with the discipline of philosophy.

I think Rodney Stark makes a substantial contribution to the study of early Christianity in posing the kinds of questions that he pursues (which reflect his social-science background).

"Religions" of the Roman world varied. Most of it was ritual practices. There were periodic occasions when cities honored their guardian deities with sacrifices and ceremonies, to ensure that they stayed happy and kept the city safe.

I think that Rodney Stark puts his foot wrong on some things where he simply wasn't sufficiently current on scholarly developments.

Some modern scholars contend that in terms of what "religion" was in that [Roman-era setting], you can't even call Christianity a religion.

Galen's observations reflect one of the distinctive features of early Christianity. Roman-era religion was mainly about ritual actions vis-à-vis the gods, and there was little to do with ordering behavior otherwise.