Zoroastrian dualism is a vision of the world as tension and conflict between good and bad. This can be expressed as a drama between good and bad dramatis personae: gods, people, nations, and beasts, but it can also be expressed existentially as a conflict or tension within every individual, or sociologically, within every community. It comes down to choices being made on a continuous basis by individuals, groups, and societies, every choice being a confrontation.
I don’t think that Zarathuštra believed in good and evil, rather, I think that he observed good and evil as facts. Joy exists, and so does suffering. They may be experienced subjectively, but their existence is an objective fact. Zarathuštra didn’t need to have faith in reality. He needed to have faith in justice.
Life is not a game. The stakes are too high, and they are elevated and accelerated — not diminished — by the fact death is ever at the door.
… Yet death arrives without an accounting. We invent narratives to make sense of death, but death doesn’t respect our narratives. It simply ends them.
We cannot be certain about what Zarathuštra really believed, but I get a sense from his hymns that he felt an urgent need for justice. I do not get the sense that he was certain that justice actually exists. He yearned for justice, he prayed for justice, and he demanded justice. Perhaps he convinced himself that justice must exist. One way or another he invented heaven and hell, and while doing so he put the gods on trial.
I dearly wish that cosmic justice were a fact. Sadly, I have not been able to contrive a personal faith in it. The only justice that I can see is the justice that a person creates in their desire for justice. That might mean that I am not a “person of faith”, but I do feel a deep empathy for Zarathuštra (as I imagine him) that renders me his faithful companion.
I resonate exactly with your phrase about the only justice you can see being "the justice that a person creates in their desire for justice." Key are "a person", that is, what arises from one's own experience and conscience, rather than the prompting of the crowd; and "desire," for though what constitutes justice in any given case may be difficult to be sure of, one cannot be too far off course if the heart, rather than some other motivator, is that which acts in justice.
Zarzathustra believed in the one God, and also believed in the afterlife. This world is a struggle between good (love) and evil (ego/and misuse of divine susceptibilities). Everything good comes from God, and everything “evil” from man. I agree personal reflection and accountability is the root of it. I have studied thousands of NDE’s, which is practically a science now, these are facts to me. Have had one myself. I can’t find anything to disagree with in what we know of Zarathustra’s teachings. I always try to balance faith with science of the afterlife (which to me is pre/physical life as well). So afterlife isn’t a real term to me, “after the current physical incarnation, returning home” better says it for me. “Rest in Peace” makes some sense because we are no longer held back by sleep, sickness, physical limitations. Zarathustra seems on point to me.