Parergon 28.2 (2011) Law of Nations as Reason of State: Diplomacy and the Balance of Power in Vattel’s Law of Nations Richard Devetak I: Introduction The eighteenth-century European states-system witnessed the development of key practices and institutions exclusive to states’ external relations. These included the establishment of foreign ministries, the incipient professionalization and expansion of resident diplomacy, and conscious management of the balance of power. 1 These practices and institutions prompted sovereigns to develop administrative machinery capable of promoting state interests in the fluid political context of a European states- system. They also afforded scholars and practitioners an opportunity to construct theoretical programmes aimed at generating or exploiting the kind of practical knowledge useful to sovereigns for the purposes of foreign policy. This essay suggests that Emer de Vattel’s Le Droit des Gens (hereafter referred to by its English title, Law of Nations), originally published in 1758, is best understood as a response to developments in the diplomatic and strategic context, articulated through the intellectual resources available under the laws of nature and nations. 2 Motivated by concern over moral and imperialist, as well as lingering confessional and dynastic, threats to Europe’s states-system, his intention was to write a practical contribution to the law of nature and nations, one capable of informing statecraft in a system composed of states with competing interests and uneven strengths. Vattel’s reconstruction of modern natural law improvised a more pragmatic, normative programme for the diplomatic management of Europe’s 1 I am grateful to Ian Hunter, Ryan Walter, Conal Condren, the guest editors of this Special Issue, David Martin Jones and Cathy Curtis, and the two anonymous referees for their helpful comments and advice. 2 Emer de Vattel, Le Droit des Gens. Ou Principes de la lois naturelle, appliqués a la conduite & aux affairs des nations & des souverains, 3 vols, ed. M. P. Pradier-Fodere (Paris: Guillaumin, 1863); I use the recently republished 1797 anonymous translation, The Law of Nations, Or, Principles of the Law of Nature, Applied to the Conduct and Affairs of Nations and Sovereigns, with Three Early Essays on the Origin and Nature of Natural Law and on Luxury, eds Béla Kapossy and Richard Whatmore (Indianapolis: Liberty Fund, 2008).