Law, War, and Casuistry in Vattel’s Jus Gentium

I: Introduction

One of the central difficulties confronting modern interpretations of early modern jus naturae et gentium is that they posit a level and kind of philosophical coherence that is not possessed by their object.¹ The law of nature and nations was not a single science or a methodologically coherent body of doctrine but a sprawling genre in which several disciplines or doctrinal bodies – theology, jurisprudence, political, and moral philosophy – were shaped and reshaped in accordance with rival cultural and political programmes.² Moreover, it was a genre in which a wide array of more concrete or technical discourses – common law, public law, military history, diplomatic history, treaty collections – were incorporated in higher-level discourses of theological or political rationality by being subjected to particular processes or practices of ‘abstraction’: for example, by being annexed to metaphysical doctrines of man’s self-perfecting rational or social being; civil discourses on man’s pursuit of security in the state via the social contract; (Stoic) humanist discourses on a society of nations grounded in man’s cosmopolitan nature; and so on. Rather than assuming a coherent body of doctrine unified by abstract theoretical or philosophical foundations, then, it is the task of the historian (as opposed to the philosopher) of jus naturae et gentium to approach his object in terms of its programmatic variety. This means that he must approach philosophical abstraction itself as an object of historical investigation, hence as a concrete activity assuming diverse forms and roles in the genre.³

In the case of Emer de Vattel’s Droit des gens (1758), the assumption that the law of nations is a discourse based on philosophical principles has had particularly damaging consequences, leading to a failure to investigate the actual operations of Vattel’s discourse and the historical circumstances in which they were mounted. This assumption is largely responsible for the conflict between those who view Vattel’s project of applying natural law to the relations between states as idealistic and impracticable,⁴ and those who treat its idealism as fatally undermined by political expediency and capitulation to the actual self-interested practice of states.⁵ The same assumption is even more emphatically present, however, in Emmanuelle Jouannet’s proposal for overcoming this conflict: by treating it as endemic in the tradition or ‘school’ of jus naturae et gentium to which Vattel was heir, which she regards as divided between positivist and naturalist forms (Hugo Grotius and Francisco Suarez versus Samuel Pufendorf and Christian Wolff), and statist and universalist tendencies (Thomas Hobbes and Pufendorf versus Gottfried Leibniz and Wolff). For, this permits her to argue in the (Kantian) philosophical–historical manner, that Vattel’s discourse is characterized by the dialectical reconciliation of these divergent tendencies, giving rise to a unifying philosophical principle for the law of nations.⁶ According to Jouannet, this principle is that of the ‘tacit agreement’ of the members of a ‘society of nations’ – each of which should be regarded as a self-perfecting ‘nation-person’ – to pursue their collective self-perfection as commanded by natural law, thereby giving rise to the ‘classic’ or ‘modern’ doctrine of international law. This solidarist agreement is supposed to impose ‘perfect’ juridical obligations on the nation-persons, thereby subordinating statist positive law to cosmopolitan natural law, and establishing the principle of (perfectionist) justice as the normative foundation of international society.⁷ Vattel can thus be portrayed as articulating the modern version of ‘just war’ doctrine – understood in terms of the collective enforcement of international juridical obligations – thereby purging his reputation as an apologist for the balance of powers and aligning his Law of Nations with the modern philosophical defence of just war in Rawls’s Law of Peoples.⁸

The problem with both of these approaches to Vattel – the one that criticizes him for sacrificing the natural law principle of justice to political expediency no less than the one that defends him for realising it in the ‘modern’ doctrine of international law – is that neither approach investigates how Vattel actually uses this principle in his discourse on the law of nature and...