Before discussing Kant’s view on how one is forced to join a state and the version of hypothetical social contract theory toward which these concerns lead Kant, it is interesting to consider the relationship between Kant’s argument for the necessity of the state and his views on international relations. Kant has argued that people who remain in proximity, and in the natural condition relative to others, because they necessarily interfere with the freedom of those others, may therefore justly be forced to join together with them in a state that secures their freedom. However, what if these people are already members of a state, but a different neighboring state? Two related problems arise: First, the members of each state interfere with the freedom of the members of the other state just as they would if they were not members of a state at all; if there is no formal relationship between the states, there is no guarantee that the members of each state will respect the rights of the members of the other state. Second, the two states, which can each be thought of as a “moral person” , are in the state of nature relative to one another, and suffer all the difficulties that let Kant to argue for the need for civil society.
Kant recognizes that these are serious difficulties which, unchecked, would very much undermine the possibility of the sort of human development that he thinks should be facilitated. His solution to the problem is to suggest that the same forces that lead individuals into a state should lead states into a federation of states . This federation of states would then fulfill the same role among states that a state fulfills for its citizens, and would also provide the necessary guarantee of external freedom among the citizens of different states.
Although it is clear what Kant provides through his suggestion of a federation of states, there is also a significant problem raised by this suggestion: Who is ultimately sovereign? Since Kant argues that for a state effectively to fulfill its role it must be ruled by an absolute sovereign, it would seem to follow that the federation of states can effectively fulfill its role only if it is ruled by an absolute sovereign. Thus, it appears to be a clear implication of Kant’s argument that there should be a single world nation, without lesser sovereign states. However, Kant never supports the notion of a single world state, and at one point discusses the concern that such a world state “may lead to the most fearful despotism”. Thus, while Kant was right to recognise that his argument for the necessity and the legitimacy of the state has important implications for international relations, he was never able to give a clear and satisfactory account of how those international relations should be organized.
(Kant’s moral and political philosophy în The Age of German Idealism (coord. R. Solomon, K. Higgins), Rougledge History of Philosophy, vol. 6, prima editie 1993, la pp. 94-95)