…the relation between love, justice, and a dualistic theory of ethics. Orthodoxy, while properly sensing the inevitability of sin in the world and the consequent defeat of pure love as a moral force, inclines to be pessimistic about the cultural possibilities of love. It tends to withdraw from the world in preference to interacting in it…Orthodoxy has not yet found the exact relation of justice to love. Individual perfection is too often made an end in itself.
The liberal ethic, contends Niebuhr, is a religious expression of the Renaissance fallacy. Enlightened on the law of love, but insensitive to the inevitability of sin in history, liberalism vainly seeks to overcome justice though purely moral and rational suasions…Liberalism confuses the ideal itself with the realistic means which must be employed to coerce society into an approximation of that ideal. Perfect justice will not come by a simple statement of the moral superiority of brotherhood in the world, for men are controlled by power, not mind alone.
— MLK, “Reinhold Niebuhr’s Ethical Dualism,” 1952