Whether Jesus is historical or fictional is only relevant with respect to whether a Symbolic Christianity or Proto-Christianity is the more appropriate for Symtheism. The greatest story ever told has several transitional purposes with respect to humanity’s progress. One of the major transitions Jesus ushered in is the change in approach to ethical behavior. This component of Jesus’ purpose starts with the beginnings of morality itself. The story of Adam and Eve is the story of man’s transition from animal to human. Adam and Eve aren’t individuals, they are characters representing the 250,000 or so generations in that transition period. Eve decides to eat from the tree of knowledge of right and wrong. This is technically correct by the way, it was the sexual selection by females that has made humanity what it is. So anyway, they eat from the tree of knowledge of right and wrong (or awareness) and immediately get dressed (cover their nakedness). This confused me for some time, knowledge of right and wrong is arguably objective morals but getting dressed is hardly a high moral principle. Then I read “Universally Preferred Behaviors” by Stefan Molyneux and it made sense, getting dressed is after all a universally preferred behavior. People developed or experimentally derived objective (at least as objective as it gets) morality over thousands of generations in the form of universally preferred behaviors (UPBs). UPB’s are flexible and can change over time but it can also be difficult to distinguish fads from UPBs thus with only UPBs to guide ethical behavior humanity was prone to shall we say missing the mark. Then humanity develops writing so we get “Moses” condensing and writing down the important UPB’s into The Law “from God”. Now the guide to ethical behavior is stable, but that means it’s also rigid and unable to adapt to changing or new situations, it’s written in proverbial stone. As Captain Pickard once said “There can be no justice so long as laws are absolute.” So humanity goes through multiple iterations of failure with this approach to ethical behavior all the while prophets are saying there will come a time when things are done differently. So then we finally get “Jesus” who extracts the moral principles from The Law. So now we have an approach to ethical behavior that is both stable and flexible. The principals don’t change but they can be applied to new and changing situations. It’s an excellent system and one I wish humanity had followed but alas good ole Paul comes along with The New Law “from Jesus” and takes us a step backwards, but that’s a tale for another day.
Obviously, the entirety of Jesus’ teachings couldn’t be covered in a few lines but I would like to mention probably his most famous directive: Love thy neighbor as yourself. The word love in this context is an action not an emotion. Thus, it could be taken as treat others as you would want to be treated; but also as generously interpret what others say as much as you would want what you say to be generously interpreted. What I’m getting at is that while the principle is the same as it was two millennia ago, the application is flexible enough to be a sound guide to ethical behavior today.