Washington ? Next Thursday marks the 40th anniversary of one of the greatest days in American history — the day of the massive March on Washington for Jobs and Freedom, the largest civil rights demonstration of them all and the one that climaxed with Martin Luther King’s “I have a dream” speech that ranks as one of the transcendent legacies of American rhetoric.

Even after four decades, I can vividly recall the emotions felt by everyone in that crowd of a quarter-million people filling the Mall and stretching back toward the Capitol, as King stood at the feet of Abraham Lincoln at the memorial to the Great Emancipator and filled the air with his vision of a nation where “my four little children will one day live in a nation where they will not be judged by the color of their skin but by the content of their character.”

In a brilliant essay in the summer issue of The Public Interest, Adam Wolfson, that journal’s editor, expounds the meaning of that famous passage. Although King was speaking extemporaneously at that point, drawing on remembered portions of past addresses, his words were carefully chosen. In one earlier speech, he had said America should seek to “substitute an aristocracy of character for an aristocracy of color.”

But judging people by character does not equate, as so many, including Justice Clarence Thomas, have argued, to judging each individual on the basis of talent and ability regardless of race.

“When King spoke of character,” Wolfson writes, “he had a different meaning in mind. Character is not something we are born with, and it is not measurable in an IQ score or a talent contest. Rather, it is something we develop over a lifetime in the course of our moral education.”

King’s entire life — like his speech that day — was an exercise in moral education. Imbued with the spirit of passive resistance, he argued that the means by which civil rights were gained were just as important as the ends. Few of us in the white majority grasped that point before the march demonstrated it.

I had been called back from vacation by my editors at the old Washington Star, because they — along with the entire political and business establishment, including President Kennedy — feared there might be trouble with so many outsiders descending on the city.

As Drew Hansen notes in “The Dream,” his newly published book about the march, civil rights legislation was stymied in Congress. Anti-black violence, including the murder of Medgar Evers, meanwhile, had inflamed passions. No one knew what thousands of frustrated protesters might do, and, as Hansen writes, “Washington had barricaded itself against the invaders. The streets downtown were nearly deserted. … There were so many soldiers on the streets one senator remarked that it looked as though a military coup had happened during the night.”

Instead of trouble came inspiration — with the peaceful black marchers (joined by a surprising number of white clergymen and other sympathizers) providing a powerful political impulse that spurred the passage of the great Civil Rights Act of 1964 and the Voting Rights Act a year later.

Last month, John Lewis, the only survivor of the six men who led the March on Washington, organized a commemoration ceremony in the Capitol. Then the 23-year-old head of the Student Non-Violent Coordinating Committee, whose skull was scarred by white vigilantes who had mobbed the Freedom Riders, Lewis has been the representative from Atlanta since 1986, revered in both parties as the moral conscience of Congress.

His remarks at the ceremony, like Wolfson’s essay, made an important point. King’s speech moved the country, not because it challenged Americans to accept new ideas, but because it so powerfully invoked the values on which the nation was founded — the belief in freedom, justice and equality under law. “Call it the spirit of our Founding Fathers,” Lewis said last month. “Call it the spirit of Abraham Lincoln, Teddy Roosevelt or FDR. Call it the spirit of the March on Washington. Call it the spirit of history.”

Bill Frist, the Senate majority leader, told the gathering that Aug. 28, 1963, was one of those moments in history “when we are reminded that our nation is not simply stumbling along a directionless path, but instead is guided by Providence toward a righteous and noble destiny.”

The Tennessee senator quoted King’s own assessment of the March on Washington: “As television beamed the image of this extraordinary gathering across the border oceans, everyone who believed in man’s capacity to better himself had a moment of inspiration and confidence in the future of the human race.”

It was all of that.