Karl Paul Reinhold Niebuhr was an influential pastor and theologian in America. His thought initially centered on liberal pacifism, but it later turned to the program of the social gospel and, finally, to ‘Christian Realism’. Niebuhr’s father was a German immigrant Protestant pastor; his mother also came from an immigrant pastor’s family. Niebuhr completed his theological education at Eden Theological Seminary (Webster Groves, Missouri) and Yale Divinity School, and he was ordained in 1913.