Kant (1724-1804), who is the best known representative of the cosmopolitan understanding, discusses ethics and reason in his studies, as well, and he takes on hand the concepts of peace and war as the basic phenomena of social structure. According to him, an individual has the freedom to choose right, ethic and moral, and his behaviors are not determined in advance. But, he has responsibilities and obligations to perform and to obey to the ethical laws accepted as right by universal reason. The ethical laws are known to individuals, and they are universally obligatory
rules for all humankind. The universal dimension of Kantian ethics is accepted as fundamental in IR. In Kantian idealism, there is an understanding of cosmopolitan international society which is composed of individuals, states and other actors adopting ethical principles. Right reason which has a different character transcends the law made by states, necessitates to fulfill states’ responsibilities stemming from universal law. This indicates the way toward the state of perpetual peace. A world federation formed by peaceful states was introduced by Kant as a recipe to solve the security demands of states. According to these information, the correct answer is given in the option D.