  The legal-moral obligation or obligatoriness of a legal rule is counterpart to the legal-moral authority or authoritativeness of its author (enacter) or other source. The idea of authority has been clarified by contemporary legal theorists such as Raz and Hart, by reflection upon the kind of reasons for action purportedly given to potentially acting subjects by an exercise of practical authority. The relevant kind of practical reason has been variously called exclusionary, peremptory or pre-emptive, and content-independent. The core idea is that subjects are instructed to treat the proffered reason (say, a statutory provision, or a judicial order), in their deliberations towards choice and action, as a reason which does not simply add to the reasons they already have for acting one way rather another, but rather excludes and takes the place of some of those reasons. And this exclusionary, peremptory or pre-emptive force is owed not to the inherent attractiveness to reason of the (content of the) proffered reason, but to the status of its author or other source as one entitled—for example, by its role in a constitutional scheme of governance for the solution of a political community’s coordination problems—to be obeyed, complied with, treated as authoritative. See e.g., Raz 1986, 35–69. This content-independence of authoritative reasons entails their presumptive obligatoriness. The defeasibility of that presumption is entailed by the dependence of such reasons’ peremptory, pre-emptive or exclusionary force upon a background of presupposed basic human needs and goods, and of basic moral principles and norms, a background which entails that if a purportedly authoritative proffered (posited) reason conflicts sufficiently clearly with those standing needs, goods, principles or norms its exclusionary force is exhausted or overcome and the purported obligatoriness defeated.