Grotius’s Sources of Ius Gentium Slavery

Abstract Grotius’s discussion on slavery exhibits a dual character, as it is based on natural law on the one hand, and on ius gentium on the other. This article focuses on the sources used by Grotius in his search for the rules of ius gentium on war slavery, and compares Grotius’s insights with the works of some of his contemporaries. After briefly discussing Grotius’s introduction to ius gentium and its sources, his references to three themes concerning war slavery are analyzed. The research shows that, if need be, Grotius works according to his own rules even though it seems difficult for him to leave Greco-Roman antiquity and Europe behind; it also shows that he is content with flimsy evidence. In addition, analyzing his sources informs us about Grotius’s personal input regarding the legitimacy of war and slavery. It turns out that with regard to one of the most far-reaching principles concerning war slavery, Grotius’s insight is consistent with what seems to have been generally accepted among (European) scholars from antiquity to his own time. Another lesson learned: natural rights are not safe with Grotius, since ius gentium as presented by him is a serious threat to such rights.