The Fathers lived in a time when religious pluralism was a given reality
Roman Civil Religion (Roman Pantheon and city gods)
Stoics
Epicurean
Cynics
Pythagorean
Platonism, Neo-Platonism
Mystery Cults
"Oriental" Religions (e.g. Zoroastrianism and Judaism)
Atheists
Brief, localized periods of persecution punctuated long swathes of indifference by the Romans (e.g. Christians were the pretext for Nero burning the Roman slums)
Christianity's primary self-identity was of being an exception; a minority within the world1