Abstract
Challenged by moral nihilism we have three options: some sort of “Protagorean” conventionalism, a transcendentally rooted version of “naturalism” originally identified by Plato and fleshed out by Augustine, and a “virtual” morality cynically marketed as objective. Conventionalism, however, fails to ground obligation, which could thus be justified only by “Augustine's” alternative, which he developed from its original in three ways: by proposing a personal first principle, thus emphasising respect for every individual; by deepening our awareness of evil in reinforcing the notion of “crime” by that of “sin” against the nature and consequent commands of a personal God; and by locating us in no timeless sphere of pure rationality but in our particular historical space. Religion (so understood) and moral obligation stand or fall together