Introduction

In the eighteenth century, diplomacy underwent a double transformation: it became permanent and it widened the scope of its interventions. Publicists and philosophers did not fail to notice this increasing importance of interstate relations. How did the men of the Enlightenment analyse this phenomenon? Diplomacy had always been the private domain of kings and princes. Did philosophers consider it a peacemaking institution or one of the many elements of a European ‘political system’ serving the reigning families? Were the reinforcement of the links between the states and the increase in the number of treaties forming the Droit public de l'Europe since the Westphalian Treaties regarded as the progress of civilising between the peoples or as a start for new claims and new conflicts? Throughout the eighteenth century, this debate poses the central question of the moral legitimacy of diplomacy and its relations with the law of peace. Although philosophers are critical of the European order and of the Machiavellian politics of princes, they still notice that peace treaties – as remote from the ‘true principles of morals’ as they are – remain of a distinctly ambivalent nature. Gabriel Bonnot de Mably (1709–85) particularly dwells on the necessary transparency of peace negotiations. According to him, diplomats should do away with the practice of vulgar politics, which consists of making treaty articles obscure; they should turn bonne foi into the cornerstone of their peaceful intentions.