H. Richard Niebuhr represents the apex of "Abel-type" Christian theology in America. He constantly worked to reconcile the nature of Christian faith with the Kingdom of God on Earth, being true to contemporary science and philosophy and the essence of Christianity at the same time. He taught at Yale Divinity School and was a mediating voice between the secular Christian activists on the political left and the biblical fundamentalists on the right.
Philosophically he wrestled with the problem of the unity of God and the disunity and pluralism of religion. He wrote about how religions are relative expressions of their culture's response to God, always conditioned by historical experience.
His book The Responsible Self calls for perfection in adult life, however the left-leaning liberation and free love movements gathering strength in American culture at the time mocked his ideal as "The Impossible Self." His critics advocated less a strenuous life marked by hedonism and acceptance of people "as they are" rather than "as they ought to be."