This week, more than any other in recent history, the traditional strategic interests of the United States have veered toward collision with the country's founding principles. President Barack Obama spent the week walking the narrow, dangerous gap between the crumbling edifice of Egyptian autocracy and the potent force of millions of people rallying for American-style democracy and rights - in other words, between the old Middle East policy of self-interested pragmatism and a new one born of principle, devoid of the certainties that had held force since the midst of the Cold War.
To trace that line, all you needed to do was listen to Mr. Obama's fast-changing characterizations of Egyptian President Hosni Mubarak.
Little more than a year ago, the U.S. President was praising the Egyptian autocrat: "He has been a stalwart ally," he told reporters during a warm-hearted meeting with Mr. Mubarak. "I think he has been a force for stability."
On Jan. 28, after hundreds of thousands of Egyptian protesters had filled the streets of Cairo for three days, Mr. Obama still seemed to be on Mr. Mubarak's side, declaring that he must respond with "concrete steps and actions that deliver."
Two days later, he strengthened his tone, calling for "a meaningful dialogue between government and citizens and the path of political change that lead to the future of greater freedom and greater opportunity and justice for the people of Egypt."
Then the balance shifted, and a different language began emerging. On Tuesday, Mr. Obama seemed explicitly to have abandoned his former ally: "My belief is that an orderly transition must be meaningful, must be peaceful and it must begin now." And then, after Wednesday's violence in Cairo's Tahrir Square, Mr. Obama's spokesman, Robert Gibbs, hammered in the final nail: "When we said 'now,' we meant 'yesterday,' " he said, expressing the President's new position. "That's what the people of Egypt want to see."
For Mr. Mubarak, this was a rather rapid journey from being America's second-most-important military and political client in the Middle East to being an undesirable autocrat. But the transition has been equally abrupt for Mr. Obama, who has transformed from a pragmatic realist who brokered deals based on American interest into something that supporters would call an idealist and opponents have characterized as weak, spineless or confused.
The Obama ideology, for the past three years, has prided itself on a certain calculated practicality, in stark contrast to the regime-changing, change-imposing conservative idealism that defined the George W. Bush years.
The President's Egyptian paradox is only a small part of a larger fissure in the fabric of history, a rupture in the logic that defined the Middle East, leaving him staring out across an empty gulf, devoid of landmarks or handholds, where the rusty scaffolding of foreign policy once stood - a sudden shift of the sort that has not been seen since the end of the Cold War.
This is Mr. Obama's blank-slate moment.
The democratic revolutions in Tunisia and Egypt - with more ruptures likely to follow - coincide with a complete breakdown in the Middle East peace process and the probable demise of America's main Arab negotiating partners in Palestine. There, too, a whole new language will be needed.
An end point was reached two weeks ago when the "Palestine Papers," a large package of peace-process-negotiation documents, was leaked to the al-Jazeera network and the Guardian newspaper.
Western governments have pursued a strategy in which Mahmoud Abbas and his Fatah Palestinian Authority government in the West Bank is given aid and political support, as well as the ever-extended carrot of a potential peace deal and independent Palestinian state, in order to isolate the radical-Islamist Hamas government in Gaza. In short, Mr. Abbas has served a role not unlike that of Mr. Mubarak. And with the leaks, Arabs suddenly saw Mr. Abbas in a very similar light.
They revealed how far Mr. Abbas's negotiators had abased themselves in their effort to reach a deal, any deal, with Israel: They had conceded almost all of the Jewish settlements in East Jerusalem, a traditional Palestinian claim; they had agreed to restrict their long-demanded "right of return" for expelled Palestinians to a limit of 10,000 a year; and they had actively co-operated with Israeli security forces during the 2008 attack on Gaza - and then had been utterly betrayed when Israeli leaders were unwilling or unable, whether through democratic deadlock in their coalition governments or simple stubbornness, to agree to any of it.
Not only did the papers reveal how thoroughly the old logic of the peace process had collapsed - how absolutely everything had been attempted and failed - but they also revealed, and actually helped to accelerate, the end of the strategy of legitimizing Mr. Abbas's movement and marginalizing Gaza's Islamists. This occurred just as relations between the U.S. and Israel had reached a deadlock, with Israeli Prime Minister Benjamin Netanyahu defying every effort of Mr. Obama to create an opening or even to halt the construction of new settlements in order to restart talks.
Given this, it may not be so much that Mr. Obama has made a sudden shift from pragmatism to idealism as that American national interests have changed. Republicans and many Democrats traditionally argued that having friendly, autocratic Arab regimes matched with an Israeli stalemate was valuable as a source of "stability." But that structure, put into place when America's chief fear in the Middle East was Soviet-backed communism rather than Islamic extremism, has not been yielding much stability lately. It has become all too apparent that the violent actions of al-Qaeda and other movements have been spurred and provoked, rather than quashed, by Arab authoritarian regimes.
Israel's peace agreement with Egypt and its tacit understanding with Jordan, in this light, were not the first steps toward a wider peace, but the end points of a failed process. The sealed southern border with Egypt has turned the Palestinian refugees of Gaza into a desperate and increasingly radical community, isolated from the broader Arab world. The old "stability" was the root cause of the new instability.
So, while a few voices from the Republican Party (such as former United Nations ambassador John Bolton) have suggested that Mr. Obama is spineless or is selling out America's best interests, the party's mainstream generally has fallen in behind the Democratic President this week.
With good reason: What's happening in the Middle East this year, an apparent cascade of popular-democratic revolutions, is almost exactly what George W. Bush was attempting to spur by invading Iraq. The neo-conservative thinkers who had his ear in his first term virtually spelled out this scenario in their Project for a New American Century manifesto: The only challenge, they said, would be to make the newly empowered Arab voters side with the U.S. for having inspired them. But Mr. Bush backed away, eventually, after Iraq failed and his modest push toward Arab democracy brought Islamists to power in Gaza.
While Mr. Obama appeared embarrassingly awkward in his tiptoe toward support for Egypt's democracy movement this week, the hesitancy was understandable: Egypt marks the nadir of a certain path in U.S. foreign policy, beyond which is a blind step into the unknown.
There are two possible outcomes, and they may arrive quickly. The first is that the new Middle East becomes a bold symbol of America's new irrelevance in world affairs and of the U.S. president's impotence; the newly emboldened Arab publics, already harshly anti-American, turn even further from the United States, embracing new powers to the east or even Islamic parties; and Israel remains an American ally, but its old hope as an anchor of democracy in the region will be long forgotten, its fate in its own hands.
However, there is another option. The democracy movements in Tunisia, Egypt and elsewhere have not been explicitly anti-American: Burning Uncle Sams or stars of David have not been their icons, and those messages haven't seemed to interest the protesters. This could be an opening for the U.S. to engage in a more realistic way with the people of the region, bypassing or abandoning the unrepresentative, autocratic leaders who have never had much legitimacy. The old "Cold War logic" never actually made sense: It was anti-democratic and it prevented the economic progress that might have ended the terrible impoverishment of the Arab people and, with it, their increasing radicalization.
Mr. Obama may have stumbled over Cairo, and he may yet trip over his feet into another, Afghan-style crisis of powerlessness - one that, given the symbolic importance of the Middle East to much of the world, could be terribly damaging.
But there is still an opening, one he created on his first presidential visit to Cairo almost two years ago. Most Arabs, rich and poor, remember his words in 2009: "I've come here to Cairo to seek a new beginning between the Untied States and Muslims around the world, one based on mutual interest and mutual respect."
It is not too late to turn that "new beginning" from a platitude into an international policy. His ability or failure to make that happen may turn out to be his ultimate test.
Doug Saunders is a member of The Globe and Mail's European bureau.