Early Christians were strong believers in natural law, that God has revealed, we might say, rudimentary elements of eternal truth to all mankind, to every culture. That you can take any pagan, it doesn't matter what country they lived in or that they might live in today, they have had natural law revealed to them. They might be cannibals, but their conscience, they've had to sear their conscience. Their conscience would tell them that is wrong. Most human cultures have viewed that, have recognized that as wrong.