There were experiences in previous centuries which might well have challenged this unqualified optimism. But the expansion of man's power over nature… - Reinhold Niebuhr

The separation of church and state is necessary partly because if religion is good then the state shouldn't interfere with the religious vision or with the religious prophet. There must be a realm of truth beyond political competence, that's why there must be a separation of churches, but if religion is bad and a bad religion is one that gives an ultimate sanctity to some particular cause. Then religion mustn't interfere with the state — so one of the basic Democratic principles as we know it in America is the separation of church and state. ... A church has the right to set its own standards within its community. I don't think it has a right to prohibit birth control or to enforce upon a secular society its conception of divorce and the indissolubility of the marriage tie.

Man's capacity for justice makes democracy possible, but man's inclination to injustice makes democracy necessary.

It would have been too much to expect of religion that it find an immediate antidote for the naturalism and secularism which the modern scientific world view has created. It was inevitable that the natural world, neglected for centuries, should take vengeance upon the human spirit by making itself an obsession of the human mind. But it cannot be said that religion has been particularly wise in the strategy it developed in opposition to naturalism. Religion tried to save itself by the simple expedient of insisting that evolution was not mechanistic but creative, by discovering God in the evolutionary process. Insofar as this means that there is room for freedom and purpose in the evolutionary process, no quarrel is possible with the defenders of the faith. But there is, after all, little freedom or purpose in the evolutionary process — in short, little morality; so that if we can find God only as he is revealed in nature we have no moral God.