Determining the starting point of the discipline of international law has always been subject to controversy in the academic world. The divergent views on the genesis of international law reach from the Egyptian-Hittite Peace Treaty over the Peace of Westphalia on to a meeting of 15 international lawyers in 1873.

It is no secret that international relations have always been embedded in normative systems. Thus, international legal historians may justifiably argue that international law dates back to at least the Peace Treaty between the Egyptians and the Hittites in 1258 B.C. or, even earlier, to the first time any two tribes established primitive political, economic or social relations. However, such a broad historical view cannot be considered as a fruitful approach in order to determine the starting point of the academic discipline of international law. This short article will present four different, commonly held views on the inception of international law in the modern age. These beginnings have been called by Maximilian Baldinger the Tordesillian, Westphalian, Vattelian and Gentian paradigms of international law. While each approach has its merit, Martti Koskenniemi’s historical thesis, which attributes the nascence modern international law to a lunch meeting on 8 September 1873 in the Flemish city of Gent, is particularly compelling.

Wilhelm G. Grewe, a former German diplomat and renowned Professor of international law, argued that the origin of international law is rooted in theological scholarship on the moral and legal issues of the early colonial era. The political expansion of Europe sparked intense academic debate primarily at the University of Salamanca in the late 15th and early 16th centuries. Among the academic protagonists were the Dominican theologians Francisco de Vitoria, Francisco Suárez and Bartolomé de las Casas. Grewe supports the widespread perception that the Treaty of Tordesillas of 1494, which prevented an armed confrontation between Portugal and Spain by dividing the globe into a Portuguese and a Spanish hemisphere, has been the starting point of the discipline of international law.

Antonio Cassese, the first President of the International Criminal Tribunal for the former Yugoslavia as well as of the Special Tribunal for Lebanon, postulated that the political settlement of Westphalia, which put an end to an era’s most disastrous war, and the emergence of the first secular legal tradition of Alberico Gentili and Hugo Grotius should be considered as the starting points of the discipline of international law. The reason for Westphalia’s prominence in the historical account of international law is owed to the fact that it represents the core of the discipline, namely the sovereign equality of territorial states.

More recent approaches to root the origin of international law point to its emancipation as an academic discipline from theology during the Age of Enlightenment. According to this perspective, the birthday of international law is considered to be the publication of Emer de Vattel’s work Droit des Gents in 1758. One distinguished proponent of this idea is Emmanuelle Jouannet, Professor of international law at the Institute d’études politiques de Paris (SciencesPo), who regards the peak of the French Enlightenment in 1758 as the genesis of classical international law.

Finally, Martti Koskenniemi, a celebrated member of the International Law Commission, pulls the genesis yet closer to the present by arguing that international law in its modern form was an invention of enlightened and liberal legal scholars, including Johann Caspar Blüntschli, John Westlake and Pasquale Fiore, in the times of 19th century High Empire. He suggests the founding of the Institut de Droit International (IDI) in 1873 in Gent, Belgium, as a potential reference date. Koskenniemi’s argument is built upon the fact that by the foundation of this institution a distinct academic discipline was born which had its own journals and professorships.

All attempts to determine a starting point for international law as a discipline are qualified by a certain degree of arbitrariness. Consequently, the goal of international legal history can only be to encourage a wide, diversified perspective on the origins and the development of international law in order to allow for a comprehensive understanding of this malleable legal discipline. However, the main reason for the endorsement of Koskenniemi’s approach is largely owed to the historical fact that the founding fathers of the IDI in 1873 for the first time embarked on considering themselves not as theologians, philosophers or diplomats merely dealing with legal issues, but as proper ‘international lawyers.’