The weaknesses of the spirit of love in solving larger and more complex problems become increasingly apparent as one proceeds from ordinary relations between individuals to the life of social groups. If nations and other social groups find it difficult to approximate the principles of justice, as we have previously noted, they are naturally even less capable of achieving the principle of love, which demands more than justice. The demand of religious moralists that nations subject themselves to “the law of Christ” is an unrealistic demand, and the hope that they will do so is a sentimental one.

Reinhold Niebuhr (1892-1971) American theologian and clergyman

Moral Man and Immoral Society (1932)