It is also thought that Hugo Grotius was not the first to formulate the international society doctrine, but he was one of the first to define expressly the idea of one society of states, governed not by force or warfare but by actual laws and mutual agreement to enforce those laws. As Hedley Bull declared in 1990: "The idea of international society which Grotius propounded was given concrete expression in the Peace of Westphalia, and Grotius may be considered the intellectual father of this first general peace settlement of modern times." Additionally, his contributions to Arminian theology helped provide the seeds for later Arminian-based movements, such as Methodism and Pentecostalism; Grotius is acknowledged as a significant figure in the Arminian-Calvinist debate. Because of his theological underpinning of free trade, he is also considered an "economic theologist".