He spoke of the promise before he spoke of the dream.

In the first part of the momentous speech he gave at the Lincoln Memorial, the part schoolchildren don’t memorize and pundits never quote, Martin Luther King Jr. reminded a watching world that in writing the Constitution and the Declaration of Independence, the founders were “signing a promissory note to which every American was to fall heir.”

“This note,” said King, “was a promise that all men, yes, black men as well as white men, would be guaranteed the unalienable rights of life, liberty and the pursuit of happiness.” His evocation of this great American promise may be less well-known than King’s description, moments later, of his great American dream, but there is, nevertheless, a straightforward clarity to it that compels.

Because where race is concerned, what is American history if not the story of how that promise was repeatedly broken? As King put it five years later in the last speech of his life, “All we say to America is, ‘Be true to what you said on paper.”‘

But America never did.

Except that now, here comes Barack Obama, son of a Kenyan and a Kansan, striding to the podium to accept the nomination of his party for president of the United States. It comes 45 years to the very day after King said he had a dream America’s promise might someday be fulfilled, 100 years and a day after the birth of the president, Lyndon Johnson, who helped nudge that dream toward reality. The timing requires you, if you have any music in your soul, any “soul” in your soul, to reappraise both the promise and the dream.

That’s what we’ve been doing lately in our various ways in our various Americas. On the sidewalk outside a Gladys Knight concert, a vendor sells a T-shirt depicting King and Obama shaking hands above the legend, “Sometimes, dreams come true.” Meanwhile, they are passing around a “joke” on the Internet that has Obama picking Sylvester Stallone as his running mate: “Rambo and Sambo,” goes the punchline.

The two extremes have one thing in common: slack-faced disbelief. Could it be? Could it really be?

Apparently, it could.

The realization coalesces something some of us never dared hope and others never dared fear: the idea that one day America would take its promise seriously.

And if that realization requires African-Americans to recalibrate their cynicism about what “they” will and will not allow black folks to achieve, it seems plain that the greater shock and sense of dislocation is borne by “they,” who must now recalibrate their assessment of what black folks “can” achieve. Small wonder “they” have responded frantically, crying with ever more shrillness that this Obama character is something other, something foreign, something strange. Something not really, truly American.

They have grown used to defining “American” as a certain skin color, a certain religion and heritage. They have forgotten that “American” was, first and foremost, a certain ideal.

Thomas Jefferson stated it thusly: All men are created equal.

The Pledge of Allegiance says: liberty and justice for all.

And King, in that speech 45 years ago, spoke of the day “all of God’s children, black men and white men, Jews and Gentiles, Protestants and Catholics” would harmonize upon a song of freedom.

Not truly American, they say? On Thursday, a nation whose credo holds equality to be a birthright will see a brown-skinned man, son of Kenya and Kansas, assume leadership of a major political party. No, it is not the panacea, not the End of Race in America. But it is striking evidence of a promise fulfilled, a dream redeemed.

How could anything be more American than that?