"I will be a better Catholic, not if I can refute every shade of Protestantism, but if I can affirm the truth in it and still go further. So, too, with the Muslims, the Hindus, the Buddhists, etc. This does not mean syncretism, indifferentism, the vapid and careless friendliness that accepts everything by thinking of nothing. There is much that one cannot 'affirm' and 'accept,' but first one must say 'yes' where one really can. If I affirm myself as a Catholic merely by denying all that is Muslim, Jewish, Protestant, Hindu, Buddhist, etc., in the end I will find there is not much left for me to affirm as a Catholic; and certainly no breath of the Spirit with which to affirm it."
— Gustav Niebuhr (Beyond Tolerance: Searching for Interfaith Understanding in America)

"The wars around the globe into which religion is woven -- violence that over the past two decades has sent many tens of thousands of men, women, and children to terrible deaths in the Balkans, Iraq, Afghanistan, Indonesia, India, Israel, the Palestinian territories, and the United States -- deeply threaten what we have of a human society. Denouncing religion itself is futile. And such simple reactions badly miss the point. It is among the religious believers that the work must be done, within that overwhelming majority who would find common ground in being human and not wanting destruction, if only because their traditions are about so much more. Those traditions contain life-giving possibilities, even if the worst demagogues would try to twist dogma so hard as to wring poison from it. "
— Gustav Niebuhr (Beyond Tolerance: Searching for Interfaith Understanding in America)

"Absolutism, in both religious and political idealism, is a splendid incentive to heroic action, but a dangerous guide in immediate and concrete situations. In religion, it permits absurdities and in politics cruelties, which fail to achieve justifying consequences because the inertia of human nature remains a nemesis to the absolute ideal...The fanaticism which in the individual may appear in the guise of a harmless or pathetic vagary, when expressed in political policy, shuts the gates of mercy on mankind. "
— Gustav Niebuhr (Beyond Tolerance: Searching for Interfaith Understanding in America)