The state of peace among men living side by side is not the natural state. A state of peace, therefore, must be established. ~ Immanuel Kant
The idea of a unified government is as old as political theory. 5th-century-bce Greek rhetorician Isocrates argued that the only cure for the incessant warfare that plagued the Greek city-states was an overarching government.
Dante rediscovered the idea of a “universal monarch,” but the modern conceptual form began with Hobbes and reached its culmination with Kant. Like Hobbes (1651), Kant (1795) envisioned a league of nations. He saw a world government not only as unworkable, but also immoral, as it violated the right of peoples to govern themselves. Rawls later (1993) concurred on this point. A league of nations may be perceived as legitimate, whereas global despotism would not.
Kant and Rawls guarded against rogues in an international league by insisting that they were “well-ordered” republics. The charter of the United Nations has no such requirement. To many critics, this is too great a concession to the inviolability of national sovereignty. The risk is that leaving despots out may only encourage their stirring international conflict.
The chief reason warfare is still with us is neither a secret death-wish of the human species, nor an irrepressible instinct of aggression, nor, finally and more plausibly, the serious economic and social dangers inherent in disarmament, but the simple fact that no substitute for this final arbiter in international affairs has yet appeared on the political scene. ~ Hannah Arendt