Even if justice should be achieved by social conflicts which lack the spiritual elements of non-violence, something will be lacking in the character of the society so constructed. There are both spiritual and brutal elements in human life. The perennial tragedy of human history is that those who cultivate the spiritual elements usually do so by divorcing themselves from or misunderstanding the problems of collective man, where the brutal elements are most obvious. These problems therefore remain unsolved, and force clashes with force, with nothing to mitigate the brutalities or eliminate the futilities o the social struggle. The history of human life will always be the projection of the world of nature. To the end of history the peace of the world, as Augustine observed, must be gained by strife. It will therefore not be a perfect peace. But it can be more perfect than it is. If the mind and the spirit of man does not attempt the impossible, if it does not seek to conquer or to eliminate nature but tries only to make the forces of nature the servants of the human spirit and the instruments of the moral ideal, a progressively higher justice and more stable peace can be achieved.
Reinhold Niebuhr, Moral Man and Immoral Society: A Study in Ethics and Politics, 256.