Immanuel Kant was well aware of the difficulties involved in establishing a cosmopolitan order. In response to the idea of a world federation, he knew that “such proposals have always been ridiculed by great statesmen, and even more by heads of states, as pedantic, childish and academic ideas.” Kant also realized that any condition of universal justice “is the most difficult to establish, and even more so to preserve, so that many maintain that it would only be possible within a [world] of angles, since men, with their self-seeking inclinations, would be incapable of adhering to a constitution of so sublime a nature.” Despite the difficulties of implementing his theory, Kant never lost faith in humankind's capacity to employ practical moral reason and to therefore eventually create a cosmopolitan order based on a mutually consistent understanding of justice and public right. As the quote above illustrates, Kant believed that the maxim of universal public right is true a priori, despite the obstacles of empirical circumstance. For it is only within a condition of universal public right that humans can enjoy an environment of secured external freedom.