Threaded through the 20,000 word essay on Barack Obama's presidency that has consumed foreign-policy observers this past week is the repeated motif that the US president is a realist, even a hyper-realist politician.
He repeatedly expresses a clear-eyed view of which problems can be tackled, and which cannot; what can be achieved by force, and what cannot; what America today is and what it is not.
In the essay by the US journalist Jeffrey Goldberg, the locus of this policy, the example around which the essay is hinged, is the unexpected US response to the use of chemical weapons in Syria. How, in August 2013, after the Assad regime struck Ghouta with chemical weapons, the United States seemed determined to retaliate, only, hours before the missiles were to be launched, for Mr Obama to back away.
Mr Obama, to judge from Goldberg's article, interpreted the chemical weapons red line he himself had drawn in a very narrow way. He saw it being mainly about Syria and Syria's war.
But what happened at Ghouta was bigger than one war, bigger than one country. It was a question of what can be done today, in the 21st century, in full view of a watching world. The standout moments of the past 20 years — the massacre at Srebrenica, the genocide in Rwanda — have passed from the hands of politicians to historians.
But Ghouta happened while the world was watching. And the US president walked away.
Understood like that, Mr Obama did the right thing for a small country. But he did the wrong thing for a great nation.
Foreign policy doesn't occur in a vacuum. It is a complicated dance, where intentions, postures and history matter.
When the US announces a "red line" and then allows it to be violated, it changes the calculations of many policymakers in many states. It emboldens those who would oppose US policy and demoralises those who would support it. The world becomes subtly more dangerous, because the effect is to bring more people to the point where they could, perhaps, defy the US, and by proxy the international order.
It is hard to quantify all of this and Mr Obama's preference for data and analysis means he doesn't seek to. He focuses, instead, on what he sees as America's core interests. But having an international order is a core interest for the US.
The root of all this is something else. Obama is not a Washington insider. He has little time for the alliances that have formed modern America.
The British fret that he no longer cares for the "special relationship". Europeans wonder if he understands their fears of Russia. The Arabs think he doesn't adequately grasp America's long, often unhelpful, history in the Middle East.
This is what is meant when Mr thereObama is called the first “Pacific” president. He looks to Asia as America's future, and has little nostalgia for the Europe that was America's past. The ties that bind America to the Middle East and Europe hold little interest for him. He is more concerned about what can be done here and now.
At root, Mr Obama thinks of America as one country and he makes decisions based on what he thinks is right for America, right now. That may seem like a rational basis for the leader of a country. But much of the international order over the past half century has been based on the idea of America as an “exceptional” country, an empire in all but name. Mr Obama doesn't believe that; his is a more narrow conception of America's role in the world.
That realism has been hard won. The years of enthusiastic but ill-considered action by George W Bush now look like the classic overextension of great powers. It is natural that a US that has come through a great depression and two unwinnable wars would be poorer, chastened and more careful. Americans, proud of their country, don't enjoy that description — that is what lies at the heart of Mr Obama's right-wing critics who say he doesn't “love” America; they mean he doesn't share the platitudinous belief that America can do anything or everything — but Mr Obama at least recognises the truth that the US can only play a more limited role these days. The president appears keen to parcel out America's political and military capital carefully.
That, in fact, is a completely rational and understandable position, even if it is intensely hard to communicate to an American public and a world beyond still accustomed to the US as the world's policeman.
I can completely understand why Mr Obama, as the leader of a country, chose not to get involved in Syria. It would have consumed most of his time in office. But as the leader of a country that aspires to leadership beyond its borders, it was a mistake. That's the difference.
Syria could have been just another civil war, an atavistic conflict fought for unfathomable reasons in a country far from Washington.
Mr Obama's tragedy is that Syria's war, by virtue of spilling so far beyond its own borders, became not merely a great humanitarian disaster but a defining challenge for the world's leaders; he has been caught on the horns of that conflict, torn between what is expected of his office and what he aspires to achieve.
Mr Obama sees himself as the leader of a small country called America. The leader of an indispensable nation would not allow children to choke to death on chemical weapons fumes on his watch.
On Twitter: @FaisalAlYafai