Grotius is the father of modern international law, and developed many of the building blocks for subsequent attempts to establish an international order. Born in Delft, he lived through the Thirty Years’ War, and in 1625 wrote his masterpiece The Laws of War and Peace (De Jure Belli ac Pacis) after escaping from prison to France. Grotius is a defender of natural law theory, but law as founded on reason rather than on a divine order: ‘natural law is so immutable that it cannot be changed by God himself’ (see Euthyphro dilemma). Grotius converted the actual fact of self-interest and self-preservation into the foundation of morals, a natural right whose service provided the rationale for civil society. In this he was immensely influential on 17th-century political theory, and especially Hobbes. The foundation of relations between the states are that pacta sunt servanda (treaties are to be respected). From this, his Stoic respect for reason, and his experience as a diplomat, Grotius derived a substantial body of precepts and principles. Like Descartes, he caught pneumonia at the court of Kristina Wasa, and died on the way back to Holland.