1. Your belief in argumentation itself assumes, without justification, that there are prescriptive, abstract, universal, unchanging laws of logic and reason.
2. Your belief also assumes, without justification, that the unaided reason of a finite individual that is limited in the scope of its use and experiences can pronounce on what is universally true (descriptively) or is in a position to dictate (prescriptively) universal laws of reason and to assure us that these prescriptions for the brain will somehow prove applicable to the ever-changing world of matter in motion outside your individual brain.
Cordially,
That doesn't mean it's immutable, only that reasonable, rational people can make determinations on these sorts of things.
2. Never claimed they were unchangeable.
What would really be helpful, is if you could explain how celestial fiat helps morality. What does it add?