Alberico Gentili and the secularization of the law of nations

A prominent early modern Italian legal theorist and practicing lawyer, Alberico Gentili is regarded, along with Francisco de Vitoria and Hugo Grotius, as one of the founders of the science of the modern law of nations (ius gentium) and a major figure in the development of international relations. He designed a solid and autonomous framework for the law of nations based on three pillars: the Greco-Roman idea of natural law, the Justinian compilation of Roman law, and the-then novel Bodinian notion of sovereignty as supreme, perpetual, and indivisible power. Gentili freed the law of nations from excessive scholastic influences and theological importations, avoiding metaphysical developments and overly subtle dialectics. He tried to build a system based on practice and experience. His legal construction is more inductive from events, episodes, customs, and facts, than deductive from unchanged premises. Providing some new arguments, he removed religion as a valid reason for conflict and war, he advocated for the legitimacy of non-Christian regimes, especially the Ottomans, and he tried to fix the tenuous lines of separation between jurisprudence and theology and between the internal forum and external forum of canon law. Neither the pope nor the Roman Catholic Church has a place in Gentili’s systematic account. His world-famous saying — silete theologi in munere alieno! — commands the theologian not to be involved in other people’s business and was claimed centuries later by the jurisprudence of European public law to argue in favor of the secularization of the law, beyond the limits Gentili himself intended.