Original sin is that thing about man which makes him capable of conceiving of his own perfection and incapable of achieving it.

Rev. Niebuhr asserted: "Dr. Niebuhr argued this approach was a pious way to refuse to face real problems.

Niebuhr battled with religious liberals over what he called their naïve views of the contradictions of human nature and the optimism of the Social Gospel and battled with the religious conservatives over what he viewed as their naïve view of scripture and their narrow definition of "true religion". Richard Niebuhr. Among his most influential books are Moral Man and Immoral Society and The Nature and Destiny of Man the latter of which was written as the result of Niebuhr's delivery of the Gifford Lectures.