And he’s back, folks.

Niebuhr is widely regarded as one of the most significant Christian intellectuals of the 20th century. Born in 1892 in Missouri to German parents, Niebuhr was ordained in the German Evangelical Church (later part of the United Church of Christ) and taught for more than three decades at Union Theological Seminary in New York. He was a founder of the liberal anticommunist lobbying group Americans for Democratic Action, and in 1948, he appeared on the cover of Time magazine.

Over the years, Niebuhr won the admiration of political figures on the left and the right, including the late historian and Kennedy aide Arthur Schlesinger Jr. and the late Jeane Kirkpatrick, who served as Ronald Reagan’s U.N. ambassador.

Niebuhr’s unrelenting gaze inward — at a United States he refused to herald as the world’s unquestioned savior — runs counter to the renewed sense of American exceptionalism that followed the 9/11 attacks.

Niebuhr’s Christian realism — his recognition of the persistence of sin, self-interest, and self-righteousness in social conflicts — highlights the distinction between the acknowledgment of evil’s existence and America’s own involvement in that evil.