The tensions between Barack Obama's poetry and prose reveal the dilemmas at the heart of the future of the west - and the world.
It isn't often that former prime ministers, the Cabinet and the entirety of Britain's lawmakers are kept waiting while one man tours the Palace of Westminster. But for most of those present, Barack Obama was worth the wait. His address in Westminster Hall, the oldest part of parliament and the first time it had been graced by an American president's speech, went down a storm.
He pushed all the right buttons, going far beyond the prediction of one US commentator that he would 'make nice' over the special relationship. Obama cited deep historical roots, ties centuries older than that little spat over "tea and taxes". He quoted Winston Churchill. He directly compared the beaches of Normandy with the Balkans and, latterly, Benghazi.
Obama's emphasis on the "struggles of slaves and immigrants, women and ethnic minorities, former colonies and persecuted religions", which had taught both Americans and the British that the "longing for freedom and dignity... beats in every heart" wasn't just rhetoric. It was the cornerstone of his speech. He returned to it in his conclusion, when he explained how "our patchwork heritage is an enormous strength". When Obama said it was this shift which enabled "the grandson of a Kenyan who served as a cook in the British Army to stand before you as president of the United States", MPs and peers broke into spontaneous applause.
He had woven his spell with all the rhetorical magic he could muster. It was a masterful performance. But it didn't deserve the sentiments from the Lord Speaker that the president transcended that old cliché about campaigning in poetry and governing in prose. Far from having succeeded in glossing over the gritty realities of power in the White House, the leader of the free world's idealised vision only served to throw into even sharper contrast the difference between the audacity of hope and the uncertainties of real life.
You only needed to have watched Obama's performance just a couple of hours beforehand, in his joint press conference with David Cameron, to get a sense of the difference.
The biggest foreign policy headache at the moment is Libya, where the US and Britain are seeking to overthrow Muammar Gaddafi without sending in ground forces. "We are doing things in a different way," Obama explained. "Even as we promote the values and ideals that we care about... we are using military power in a strategic and careful way." That fits with the ideals. But it has its weaknesses, as he was forced to admit. "Once you rule out ground forces, there are going to be some inherent limitations to our air strike operations." Like not guaranteeing that Gaddafi will be out of power any time soon, for example.
Obama's policy in Libya is considered and intelligent. It is determined to be multilateral, to take place with the consent of the region. Above all, it fits in with Obama's version of America's core values - those values shared with Britain, as the president explained yesterday.
What a change from the gung-ho interventionism of George Bush and Tony Blair. But this policy has its downsides, too. Sometimes, following up on ideals and principles means confronting apparent compromises on the ground. Libya is just one example among many: the fudged approach to the Middle East peace process and the uncertainty over how to cope with the Arab Spring, are others.
So the reality of being the leader of the free world - this leader of the free world, at least - is the day-to-day pressure of making nuanced decisions, a far cry from the comforting truths of his speeches. Those decisions don't have the same reassuring black-and-white feel as those made by Bush. More significantly, often - as in Libya - they won't come up with the desired results as quickly, if at all.
Yet there may be a larger problem in the offing, too. Obama's speech yesterday was so wide-ranging, so broad in its scope, that it offered us a glimpse into the future. We could sense where his foreign policy approach could leave his presidency, the west, and the world.
"Our nations have arrived at a pivotal moment once more," he warned. "Profound challenges stretch before us." Above them all, beyond the fragile global economy, the threat of terrorism, the spectre of nuclear networks and the scourge of poverty he mentioned, is the threat to America's sole superpower status.
"The international order has already been reshaped for a new century. Countries like China, India, and Brazil are growing by leaps and bounds," Obama continued. He did his best to downplay this change and insist that "the time for our leadership is now". For once, the rhetoric became unconvincing. He undermined his inherent confidence in the status quo, based purely on those values, by acknowledging that "this doesn't mean we can afford to stand still".
What steps, then, did he have to offer Britain, the US and the west that they could preserve their pre-eminent position? Only a need to guard against "threats of market failure", and an injunction to stay on top when it comes to "science and cutting-edge research".
Yes, of course it is good news that other countries' economies are growing. "It has lifted hundreds of millions of poverty around the globe." But in the hard world of realpolitik, the world where raw power is all that matters, pointing this out doesn't negate the shift.
As Obama's speech yesterday showed, he has no answer to those unstoppable powers rising in the east. Which is why the principles motivating his actions in the Middle East could yet apply to the shift in power away from the west.
"We will proceed with humility, and the knowledge that we cannot dictate every outcome abroad," he conceded. That subtle approach did not end the need for "our action, our leadership, [which] is essential to the cause of human dignity".
Balancing a cautious foreign policy with that historic impulse to stand up for what is right is something American leaders have always had to wrestle with. But with the changing balance of global power, Obama's approach could yet be seen as fundamentally different from those before it.
His may yet be judged a transitional leadership. Obama's presidency could, perhaps, be seen by history as the first to openly accept the decline of America to come.