How Hugo Grotius Invented International Law

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In this episode of pplpod, we explore the life of Hugo Grotius, the Dutch jurist, philosopher, and theologian whose writings on the sea, war, and natural law laid the foundation for modern international law. Born in Delft in 1583, in the middle of the Eighty Years' War, Grotius received a humanist and Aristotelian education from his father and entered Leiden University at 11. At 15 he accompanied a Dutch diplomatic mission to Paris, where King Henri IV called him the "Miracle of Holland," and by 16 he had published a scholarly edition and earned a law degree in France.

The episode follows Grotius's early legal career, when he defended the Dutch seizure of the Portuguese ship Santa Catarina in 1603 and developed the argument for the freedom of the seas in Mare Liberum. His alliance with Johan van Oldenbarnevelt and his edict of toleration drew him into the Dutch religious conflict between Arminians and strict Calvinists, and in 1618 he was arrested and sentenced to life at Loevestein Castle. In 1621 his wife Maria van Reigersberg and the maidservant Elsje van Houwening helped him escape in a book chest. In exile in Paris he wrote On the Law of War and Peace in 1625, arguing that law still binds nations in war. He later served as Swedish ambassador to France, died in 1645 after a shipwreck, and left a legacy of reason, restraint, and international order.

In this episode we cover...

• Grotius's childhood in Delft, his humanist education, his admission to Leiden at 11, and his early scholarship and diplomatic work in France
• The 1603 capture of the Santa Catarina, On the Law of Spoils, and the argument for the freedom of the seas in Mare Liberum
• The Arminian and Calvinist conflict, the edict of toleration, the fall of Oldenbarnevelt, and Grotius's life sentence at Loevestein Castle
• The 1621 book chest escape, his exile in Paris, the Thirty Years' War, and the natural law argument in On the Law of War and Peace
• His years as Swedish ambassador, the shipwreck and death in 1645, his burial in Delft, his reported last words, and his influence on modern international law

Source credit: Research for this episode included transcript materials and supporting Dutch Republic, early modern legal, natural law, theological, diplomatic, and biographical sources accessed October 31, 2026. Content is summarized and adapted for commentary and educational use.