Princeton, N.J.

THE Martin Luther King Jr. Memorial was to be dedicated on the National Mall on Sunday — exactly 56 years after the murder of Emmett Till in Mississippi and 48 years after the historic March on Washington for Jobs and Freedom. (Because of Hurricane Irene, the ceremony has been postponed.)

These events constitute major milestones in the turbulent history of race and democracy in America, and the undeniable success of the civil rights movement — culminating in the election of Barack Obama in 2008 — warrants our attention and elation. Yet the prophetic words of Rabbi Abraham Joshua Heschel still haunt us: “The whole future of America depends on the impact and influence of Dr. King.”

Rabbi Heschel spoke those words during the last years of King’s life, when 72 percent of whites and 55 percent of blacks disapproved of King’s opposition to the Vietnam War and his efforts to eradicate poverty in America. King’s dream of a more democratic America had become, in his words, “a nightmare,” owing to the persistence of “racism, poverty, militarism and materialism.” He called America a “sick society.” On the Sunday after his assassination, in 1968, he was to have preached a sermon titled “Why America May Go to Hell.”

King did not think that America ought to go to hell, but rather that it might go to hell owing to its economic injustice, cultural decay and political paralysis. He was not an American Gibbon, chronicling the decline and fall of the American empire, but a courageous and visionary Christian blues man, fighting with style and love in the face of the four catastrophes he identified.