Law of Nations as Reason of State: Diplomacy and the Balance of Power in Vattel’s Law of Nations

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 states-system. This reconstruction was made necessary by the realization that relations among sovereign states are fundamentally different from relations within them, and that this difference should yield characteristically different rules and institutions to manage the different political practices and problems that arise in this milieu. The transformations in statecraft and the various diplomatic and strategic developments Europe experienced in the seventeenth and eighteenth centuries provided a context for Vattel’s reception and modification of the laws of nature and nations.

Vattel’s reconstructive efforts, in attuning the law of nations to the empirical circumstances and political realities of the European states-system, granted the law of nations a certain amount of separation and autonomy from the law of nature, as if the connection between the two laws were mediated by a kind of clutch mechanism. Just as a clutch mechanism enables a user to control, limit, or adjust the transmission of power, from, say, an automobile engine to the wheels or a drill motor to the chuck, so as to deliver variable degrees of power or torque, Vattel analogously permits wielders of the law of nations a variable control over how much it engages or disengages from the law of nature. Vattel’s modifications gave rise to a law of nations which permits statesmen to adjust or limit the extent to which the moral authority of natural law empowers or constrains statecraft. This had the important political consequence for Vattel of furnishing a distinctive set of rules (and accompanying institutions) for governing the conduct of sovereign territorial states in the European states-system, and thereby emancipating international politics from the influence of universalizing Christian or imperial moralities. By so doing, Vattel reinscribed the law of nations in reason of state, and posited the idea that, when it comes to relations among states, states legitimately adhere to unique forms of moral reasoning and political calculation.

To show how Vattel’s reconstructed law of nations accommodates reason of state imperatives, the essay proceeds in four parts. First, I introduce the topic by positioning Vattel in relation both to the reason of state literature and to the law of nature and nations upon which Vattel primarily draws. Second, I provide an extended account of Vattel’s reconstruction of natural law, showing how it disengages the law of nations from the law of nature, and situating Vattel’s treatise in historiographies of the law of nature and nations. In the third part, I elaborate the diplomatic casuistry Vattel introduced into his Law of Nations, explaining how it legitimates the rights of self-preservation, security, and war in a context of changing diplomatic practices. Finally, I restate the argument that Vattel’s...