In his magnum opus, The Nature and Destiny of Man (1941), Niebuhr wrote that the Christian is "'both sinner and righteous' … Christ is what we ought to be and also what we cannot be." A wise man recognizes "that the power of God is in us and the power of God is against us in judgement and mercy." If this sounds paradoxical, that was the point. He had the sermonizer's appreciation of the power of contradictions to heighten moral awareness.

Jackson Lears expands on those inherent contradictions: