Der Vorwurf des Atheismus in den drei ersten Jahrhunderten

This study is of the concept of atheotes ("godless") in antiquity in relation to Christianity. After the observation that it was more loosely used in antiquity in general than our word atheism, Harnack quotes from Ephesians, where Paul uses it of recently converted Christians. He also includes later Christian uses of the word against pagans and heretics, and then Greek (and equivalent Latin) uses against the Christians who don't believe in their true gods.