On the one hand, foundational, on the other, sadly not nearly enough. Everything we think of as modern morality, derives from Christian moral philosophy. Yet even most theists grossly misunderstand the morality that their own scripture describes.
There’s also the small matter of two thousand years of history passing between the writing of said scripture and today. It matters not which religion we’re talking about here, all the major ones generally date back to the same period of time, the invention of writing.
In the New Testament, there is a story of Paul bringing an escaped slave to a meeting. His master was present at that meeting. Paul instructed the master to greet the slave as his brother under Christ. Romans simply did not do this. If there is one thing that Romans, indeed everyone of the day, took extremely seriously, it was social hierarchy. Social hierarchy was the source of social order.
Christians said, no, it’s Jesus that is the ruler of the home and the hearts of men, not these temporal things. It’s an old idea that had roots in Jewish ethical monotheism, the idea that morality flowed from God, not from the state or anything else.
Today we hold morality to be an abstract, universal, and absolute thing, not understanding just how Christian of an idea that is. And we hold our leaders up to Christ-like standards of goodness, not even realizing what that is. Jesus is the first, and penultimate, servant leader. The idea didn’t exist before Jesus did. Before Jesus, the greatest leader was the most martial leader, the one who could best protect the nation from external threats. The Bible tells the story of how badly the Hebrews wanted a king and how dear a price they paid for it.
Even Christianity’s core religious innovation, the thing that truly separates it from the Judaism it sought to replace, the idea found in no other religion today, informs modern morality to an extent greater than even most theists can understand. The idea that faith, not works, gets you into Heaven.
Anybody can pretend to be good, to adopt the trappings of moral uprightness. Before Jesus, before Christianity, there was no way to distinguish between false trappings, and actual goodness. Worse, there was the prejudice that material success was an obvious marker of spiritual success, that God would obviously reward the just and punish the wicked. So if you didn’t maintain the markers of success, that means God obviously punished you.
Christians got wise to this, and insisted on two things that stem from this core doctrine. First, that Christians should be self-sufficient, and work for their livings, not subsist off of wealthy patrons, which a significant part of the Roman economy of the time revolved around. Second, that anybody who wanted to be a part of the ‘body of Christ’ could merely profess belief and be accepted into the community and share in the wealth of the community. Christians were communists before the communism even had a word.
This idea reverberated through history and greatly informs our modern understanding of “who is deserving of our trust?” Many of our stories carry the moral, don’t judge a book by its cover, failing to mention that that is a very, very, very Christian idea.
Allow me to propose a mental exercise. Think about any moral principle that has served you well. The one you return to time and time again when you need guidance on a tricky real-world subject. I’d be greatly surprised if that idea didn’t come from the New Testament. And if it didn’t come from the New, it probably came from the Old. Without you even realizing it.
You had to have learned that principle from someone. They had to learn it from someone else. Moral principles don’t just conjure up out of nowhere, they’re transmitted from person to person. You heard the principle somewhere, then your life experiences show to you the truth of the principle, give you the experience that demonstrates said truth. But if you didn’t hear the principle, then you would have come up with your own approach for understanding the same events that caused you to believe in the received principle instead.
All of these moral principles are old as dirt, and they were all discussed and described in religious scripture, and debated by theologians before they were ever considered by moral philosophers.