In line with its influence, Emer de Vattel’s Le droit des gens (1757) is most often conceptualised in terms of far-reaching political intentions and epochal intellectual developments. However, the core axioms of the work constitute a surprisingly exact application of Vattel’s philosophical premises, developed within the highly specific traditions of Swiss Calvinism and the école romande of natural law, integrating Leibnizian influences. The present article provides basic context for this claim by excavating two early debates that Vattel intervenes upon as (...) an apologist for Leibniz: first, Vattel demonstrates an adherence to non-fatalist Leibnizian metaphysics when countering Swiss anti-Leibnizians in 1737–1741 and, second, in 1747 Vattel develops Leibnizian-Wolffian moral philosophy in response to Barbeyrac’s vindication of Pufendorfian voluntarism. These interventions point toward an evolving but systematic philosophical substratum, which I claim can also be found, mutatis mutandis, in Vattel’s account of the law of nations. Thus, whether applying natural law to people or states, Vattel considers both to be (moral) persons who naturally prioritise duties to themselves, this principle of self-interested utility conceived of as coterminous with altruistic virtue, and, by consequence, belonging to a universal society of moral actors. (shrink)