The Working Methods of Hugo Grotius: Which Sources Did He Use and How Did He Use Them in His Early Writings on Natural Law Theory?

This essay chapter analyses the working methods of the Dutch jurist Hugo Grotius (1583-1645), particularly his use and referencing of ‘sources’ in his early works on natural law and natural rights. Like most early modern scholars, Grotius garnished his texts with second-hand quotations of authoritative writers (the Classics, St. Augustine, Thomas Aquinas, etc.) and his marginalia with second-hand references to authoritative texts. He often obtained these materials from sixteenth-century florilegia and reference works. A case in point is Grotius’ referencing of Thomas Aquinas’ Summa Theologiae in Ms. BPL 917 in Leiden University Library. When we compare underlined passages in Grotius’ own copy of the Summa Theologiae with his references to Aquinas in Ms. BPL 917, we discover that two Catholic theologians --Thomas Cajetan and Francisco de Vitoria-- served as his reader’s guides to the Summa Theologiae, and shaped his understanding of Aquinas in crucial respects.