Could it be that it turns out that we’re that unethical mirror world, and our supposedly evil twins do in fact have it right? Do
If relativism is true, yes. If realism is true no. So?
Or could both us and our mirror world be unethical, and really only a small cluster of sentient algae somewhere in the UDFy-38135539 galaxy has by chance gotten it right, and is acting ethically?
If realism is true, they could have got it right by chance, although whoever is right is more likely to be
right by approaching it systematically.
All advanced societies will agree about 2+2!=5, because that’s falsifiable.
Inasmuch as it is disproveable from non-arbitrary axioms. You are assuming that maths has non-arbitrary axioms, but morality doesn’t. Is that reasonable?
Who gets to set the axioms and rules for ethicality? Us, the mirror world, the algae, god?
Axioms aren’t true or false because of who is “setting” them. Maths is supposed to be able to do certain things, it is supposed to allow you to prove theorems, it is supposed to be free from contradiction and so on. That considerably constrains the choice of axioms. Non-euthyphric moral realism works the same way.
If relativism is true, yes. If realism is true no. So?
If realism is true, they could have got it right by chance, although whoever is right is more likely to be right by approaching it systematically.
Inasmuch as it is disproveable from non-arbitrary axioms. You are assuming that maths has non-arbitrary axioms, but morality doesn’t. Is that reasonable?
Axioms aren’t true or false because of who is “setting” them. Maths is supposed to be able to do certain things, it is supposed to allow you to prove theorems, it is supposed to be free from contradiction and so on. That considerably constrains the choice of axioms. Non-euthyphric moral realism works the same way.