It was, in the end, a moment beyond the reach of words.

For a brief hour Tuesday, a country of clanging factories and clicking keyboards, of conflict and contention, of office conversations and street confrontations, was transformed into a country of contemplation — about hope and the potential it unleashes, about freedom and the bounty it provides, about purpose and the sacrifices it requires.

It was a momentous transition, from one president to another, from one image of the presidency to another, perhaps from one era to another. But it also marked a transition for the man at the center of the proceedings.

For Tuesday, the nation paused — not in grief but in remembrance, not in celebration but in solemnity, not in raucous joy but in quiet fulfillment — a fulfillment not only of a man’s dream but also of a nation’s promise.

Seldom in more than two centuries of American history has there been a moment of such profound symbolism. And if Barack Obama’s Inaugural Address lacked a quotation for the ages, it was because what the nation saw was so much more important than what the president said.

The nation saw millions of its people filling the Washington Mall, their eyes focused on a black man taking the oath of office at the West Front of the Capitol, two miles and 46 years away from the moment at the Lincoln Memorial when a black man pleaded for his people’s freedom, and for the liberation of us all from our most ancient civic sin.

The nation saw a black hand resting on the burgundy velvet of a Bible used to swear in the first president from Illinois, a lawyer and onetime rail splitter who saved the Union, redeemed America’s promise to future generations and freed more than the slaves.

The nation saw, in the reflecting pool of its own conscience, the better angels of our nature — angels that Lincoln alone saw even in the darkening clouds of the Civil War, that Woodrow Wilson summoned as he took America into World War I, that Franklin Roosevelt revived in the depths of a Depression both economic and spiritual, that John F. Kennedy mobilized in a hundred thoughts he sowed into the nation’s conscience, and that Ronald Reagan revived when he reminded us that America still awoke to a bright morning and wasn’t destined to expire in a dark twilight.

Seldom in more than two centuries of American history has there been an intersection of such profound symbolism.

It was more than a day of two presidents. It was instead a day of one nation, and if Obama is to be saluted for the genius and perseverance of his climb to the presidency, his Republican foes are to be celebrated as well for the grace of their withdrawal from power and the eagerness with which they embraced a moment of change that they recognized was more than just the transfer of office, a quadrennial occurrence that America — born in revolution, tested by tyranny abroad — has succeeded in converting into mere ritual.

And yet the biggest transformation of Jan. 20, 2009, may have been in Obama himself.

For until Tuesday at noon he was — this was praise and ridicule alike — mostly a man of words: author (of the most introspective and courageous memoir any president has ever written) and orator (beyond contemporary peer, perhaps the best since Webster). His ascendancy took flight on an updraft from his own words — words that brought him attention at his party’s Boston convention four and a half years ago, words that made his two books bestsellers, words that tamed the Clinton political dynasty even as they gave shape to an image of his own.

And yet one searches in vain in Tuesday’s Inaugural Address for words for the ages, words that even remotely match the deed and the day.

But there was poetry in that as well. Because in taking the oath of office, Obama no longer was trying out for the job but was performing the job. No longer was what he said most important, but instead what he did. The transfer of power works in more than one way. For two years Obama spoke truth to power. Now he has power.

Even in a speech without great applause lines there were plentiful indications of the new presidential style. He identified four areas of conflict — big government versus small, taming the markets versus freeing them, preserving American safety versus saving our freedoms, fighting global warming versus altering our way of life — and to each of them he implicitly suggested that the politics of the age had created false choices.

But mostly he said that the problems of the age had created great challenges — and opportunities. “For everywhere we look,” said the 44th president of the United States, “there is work to be done.”

Work to be done and, he will soon discover, choices to be made — choices pressed upon him at times that are inconvenient, choices thrust before him where the cost of choice is great, choices placed on his agenda where the implication of choice is tragic. This is the job he sought, the chance he worked for, the job he has shared with only four other men alive.

But it is not only the choices he makes that will define him. The questions he faces — the problems and the politics of the age — are almost more important, and not even a president controls them.

“All of our great presidents,” Franklin D. Roosevelt said, “were leaders of thought at a time when certain ideas in the life of the nation had to be clarified.” This is such a moment. The new president, in the moment he dominated Tuesday and in the moment history has provided him, has the potential for greatness. The rest is up to him and, if he can bring the nation along, to us.