he differs subtly in that he considers that the recipient of that power is the people as a whole, not a collection of sovereign individuals—in the same way, Jean-Jacques Rousseau's theory of popular sovereignty would consider the people as a collective group superior to the sum that composes it. Gabriel Vázquez (1549–1604) held that natural law is not limited to the individual, but obliges societies to respect natural rights and justice. For Suárez, the political power of society is contractual in origin because the community forms by consensus of free wills. The consequence of this contractualist theory is that the natural form of government is either a democracy or a republic, while oligarchy or monarchy arise as secondary institutions, whose claim to justice is based on consent of the governed organized in a political body. The law of peoples and international law Francisco de Vitoria played an important role in the early modern comprehension of ius gentium (the rights of nations). He extrapolated his ideas of legitimate sovereign power to relations between nations, concluding that international society as well ought to be ruled by just forms respecting the rights of all. The common good of the world is of a category superior to the good of each state. This meant that relations between states ought to pass from being justified by force to being justified by law and right. Vitoria has been referred to, along with Grotius, as the “father of international law.” Francisco Suárez subdivided the concept of ius gentium. Working with already well-formed categories, he carefully distinguished ius inter gentes from ius intra gentes. Ius inter gentes (which corresponds to modern international law) was a just agreement among the majority of countries, although being positive law, not natural law, it was not necessarily universal. On the other hand, ius intra gentes, or civil law, is specific to each nation. Many scholars have argued for the importance of Vitoria and Suárez as the forerunners and founders of the International law field, and the precursors of the seminal text De iure belli ac pacis by Grotius. Others, such as Koskenniemi, have argued that none of these humanist and scholastic thinkers can be understood to have founded international law in the modern sense, instead placing its origins in the post-1870 period. Just war Given that war is one of the worst evils suffered by mankind, the adherents of the School reasoned