This article tackles the issue of whether and how Hugo Grotius conceives of custom as a formal source of the law of nations. The main claim of it is that not only custom plays a fundamental role in Grotius’s thought, but that his reflections mark a fundamental turning point for the history of customary international law. A crucial role in this process of re-conceptualization is played by Grotius’s reading of Dio Chrysostom, whose oration On custom provides him with an integrated account of custom as a ‘normative practice’ based on rhetorical judgment (as opposed to the Scholastic interpretation of custom as reiteration of voluntary acts). Consequently, I argue that Dio Chrysostom’s text helps Grotius to transpose the question of the normative legitimacy of custom from a moral to an interpretative level. To conclude, I will show that Grotius adopts two different rhetorical strategies to prove the existence of customary norms of ius gentium.
Hugo Grotius’s Philosophorum sententiae de fato et de eo quod in nostra est potestate (from hereafter: psf) has, so far, received little scholarly attention, even though it provides us with an interesting insight into Grotius’s philosophical interests (and the intellectual debates that these interests were reacting to). This text, published posthumously in 1648 (Paris and Amsterdam) by Grotius’s wife, Maria van Reigensberg, contains translations of texts from various philosophers on the question of fate.
The aim of this article is to 1) place the debate on fate, in which Grotius was actively involved throughout all his life and career, in the wider context of the theological and philosophical debates on free will and divine foreknowledge; 2) acknowledge the importance played by Grotius’s psf, a gnomological collection of philosophical sources ranging from Pythagorean philosophers to early patristic authors all providing different, although converging arguments in favor of the existence of free will; and 3) suggest that debates on fate are distinctively linked by Grotius with those on the importance of law and punishment as a guarantee of order. This “legalistic” interpretation of fate ultimately allows Grotius to reconcile divine decrees with human liberty.
This chapter provides an outline of Emer de Vattel’s doctrine of the customary law of nations. Whereas the importance of custom in the doctrinal debates concerning contemporary international law has been widely acknowledged, an assessment of its fundamental role within Vattel’s account of the law of nations is still missing. I argue that its significance can be interpreted along two lines of inquiry. First of all, in light of Vattel’s critique of Wolff, according to which Vattel replaces the Wolffian perfectio as the basis of natural law with a ‘noble’, anti-Hobbesian, concept of self-interest. Custom is, consequently, conceived of as a peaceful means for states to pursue their own interests according to natural law and without necessarily conflicting with each other. Secondly, the concept of custom allows Vattel to mediate between natural law and the voluntary law of nations, by providing states with a flexible and dynamic source of obligation, mostly consisting in an overlap between the principles of natural law and the facts of international life.