This introduction presents an analysis of Grotius’s treatise ‘On Public Partnership with Unbelievers’ (De societate publica cum infidelibus). It was probably written between 1606 and 1609, when Grotius served as a legal advisor of the Dutch East India Company (voc). In his treatise, Grotius explains what kinds of partnerships with non-Christians are permissible under divine and natural law. These include public partnerships, such as treaties and military alliances, but also private associations, such as commercial contracts, marriages and relations of servitude. (...) As we argue in this introduction, De societate can be interpreted as a general treatise on legal partnerships with non-Christians, which relates both to the voc’s policies of treaty and alliance-making in the East Indies and to debates about the legal status of religious minorities in the Dutch Republic. (shrink)