Sorry for the delay.
I'm trying to make sense of what kind of thing this axiom would be. We certainly have axioms in math, but these axioms are used as starting places for
a priori knowledge. They don't purport, in themselves, to describe anything about the universe. We just use them as starting places to make logical deductions.
But your proposed ethical axiom is different from this, because you're meaning to not just make a starting place for logical deductions, but you're also making a claim about how the universe
actually is. Your axiom is that something about the universe
just is some way, that some fact about the universe
just is true, namely that God
just is supremely good. And that seems like a much more peculiar thing to do than just setting up some initial rules for a complex logic game as we do in math.
Can you think of other possible axioms like the one you proposed to compare it to? I think that if your ethical axiom is the only thing of its kind that we can think of, then it doesn't speak well to its viability.
For more of a criticism qua ethics, I think by introducing an axiom like this to solve a problem you're creating one in the process. You're introducing an axiom to avoid having to provide an ultimate reason for why good things are good. But ethics seems to resist this kind of solution. We want to say that things are good for a reason. We want to say that what's good isn't completely arbitrary. But an axiom is at odds with our expectations, as an axiom says that somthing is true for no reason and completely arbitrarily.
One of the enormous challenges in ethics is the problem of normativity, i.e. trying to answer the skeptics' question, \"Why
should we do what's right?\" You might answer that it makes people happy, but then the skeptic asks why should we make people happy, and so on. It's not clear to me that your solution actually solves this in a meaningful way. Although... if you append to your axiom, \"And this axiom solves the problem in a meaningful way!\" then the philosophical problem is solved, right?