I will argue that the Christian outlook or at least a biblical outlook has always existed. No question most or many were raised without, say, the Ten Commandments on the wall. But I think we still pretty much knew.
A bit sticky but sums it up:
“ 12 For as many as have sinned without law will also perish without law, and as many as have sinned in the law will be judged by the law 13 (for not the hearers of the law are just in the sight of God, but the doers of the law will be justified; 14 for when Gentiles, who do not have the law, by nature do the things in the law, these, although not having the law, are a law to themselves, 15 who show the work of the law written in their hearts, their conscience also bearing witness, and between themselves their thoughts accusing or else excusing them) 16 in the day when God will judge the secrets of men by Jesus Christ, according to my gospel.” (Romans 2)
I was raised an atheist - admittedly in the US which is generally a Christian culture. I pretty much knew when I did wrong as a kid. Not perfectly. But overall.
I am certain when a slave owner anally raped a servant boy or orgies of some sort were held or murder over an adultery was committed they knew they were doing evil.
I don’t look down on them like we are so great. I just don’t glorify or accept their behavior as somehow ok.
I will argue that the Christian outlook or at least a biblical outlook has always existed.
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Then that POV would be against all historical evidence for the time, the place, and the prevalent cultures.