When did Reinhold Niebuhr write "Moral Man and Immoral Society" and argue Christian Realism?
Christian Realism: Christian Realism is a philosophical perspective developed by the theologian and public intellectual Reinhold Niebuhr in the late 1940s and early 1950s. Reinhold Niebuhr:  A public theologian, he wrote and spoke frequently about the intersection of religion, politics, and public policy, with his most influential books including "Moral Man and Immoral Society" and "The Nature and Destiny of Man", the second of which Modern Library ranked one of the top 20 nonfiction books of the twentieth century.
the twentieth century