The Nature and Destiny of Man has as its major theme the need for a synthesis of Renaissance and Reformation insights dealing with the possibilities and limits of human existence, in light of the Christian understanding of grace and forgiveness.

In the first volume, Human Nature, the author reviews classical, Christian, and modern views of human nature and makes the point that Biblical faith, with its emphasis on the universality of sin, contrasts with modern people's essentially easy conscience. One main emphasis of Western culture was the sense of individuality rooted in the faith of the Bible. Human Nature traces the development of that sense of individuality. Chapter 1 "Man as a Problem to Himself" examines classical, Christian and modern understandings of human nature. Chapter 2 "The Problem of Vitality and Form in Human Nature" presents rationalistic and romantic approaches to human nature. Chapter 3 "Individuality in Modern Culture" various conceptions of individuality. Chapter 4 "The Easy Conscience of Modern Man" addresses how idealism attempts to depreciate the pervasiveness and perserverance of evil. In Chapter 6 "The Relevance of the Christian View of Man" Niebuhr argues the Christian view of human nature is more adequate for understanding human nature than the modern view. Chapters 6 "Man as Image of God and as Creature", Chapter 7" Man as Sinner"and Chapter 8 "Man as Sinner (continued)" continue to make the case outlined in Chapter 5. Chapter 9 "Original Sin and Man's Responsibility" examines Pelagian and Augustinian doctrines as well as the ongoing responsibility despite the inevitability of sin. Chapter 10 "Justitia Originalis" examines original righteousnes.