Barack Obama has called him "one of my favorite philosophers." John McCain wrote that he is "a paragon of clarity about the costs of a good war." Andrew Sullivan has said, "We need Niebuhr now more than ever." For a theologian who died in 1971, Reinhold Niebuhr is maintaining a remarkably high profile in the twenty-first century.
In Why Niebuhr Now? acclaimed historian John Patrick Diggins tackles the complicated question of why,...