"When you can, you should." That was Tony Blair's opinion on intervention, as boiled down for a journalist a few days before sending British forces into Iraq.
The world has no shortage of dictators and despots. The Blair formula was that when such human-rights violators looked vulnerable, and provided you had the military capability and political will, you should seize the opportunity. Which he did - preventing genocides in, among other places, Kosovo and Sierra Leone. In those days, Britain punched above its weight. How long ago that seems.
The nature of 24-hour multimedia means that popular calls to intervene come faster than ever. A natural disaster occurs, a country erupts or a government begins to massacre its people and within hours "something has happened" turns into "something must be done". And our politics are as reactive as our media.
If Gaddafi turns foreign mercenaries on to the Libyan people or Assad chucks out the press and gets down to a good month's massacring, the human-rights lobby and other elements on the left will insist that something must be done. Those on the political right tend to be more sceptical of demands for action. Not because they are any less bothered by the murder of civilians, but because they are suspicious of the utility of force in such situations and fear protracted involvements abroad. So those who most desire the ends are suspicious of the means, while those most reconciled with the means are suspicious of the ends.
The practical demonstration of this divide is happening right now over the Middle East and North Africa. But underneath that debate is a larger and more unremarked-upon event, a symptom of the greatest geo-political shift of our time. It took a month to institute a no-fly zone and targeted strikes on government forces in Libya. But then Assad followed Gaddafi's lead. And the chorus of "something must be done" came again. Yet nothing happened.
HMG will act tough over a single conversatory in Jerusalem
This was not because we shouldn't intervene but, rather - and straightforwardly - because, since we intervened in Libya, we can't do so in Syria. "When you can you should" has become "Well, we don't, because we can't."
In Washington the other day, I listened to Defence Secretary Robert Gates giving his farewell speech. He explained that the cuts in US military spending were not simply part of a budget-saving exercise but an effort to encourage America's allies to step up their commitments. It was hard not to emit a sarcastic "hah". The reality is we are diminishing our forces in unison. Europe has no intention of filling the gap left by America's reducing global ambition.
So we should get used to this. It is what it feels like to be a declining second-rate power when the hyper-power you relied on for decades decides to downgrade its role. You might still talk the language of moral obligations, you may still say "something must be done", but ever more often things come up that you can simply do nothing about.
When the populations of the Middle Eastern dictatorships finally rise up against their leaders, you are in no position to assist them. When pro-democracy activists in Syria get gunned down in the streets by the dauphin of Damascus you cannot go their aid. When, in a swiftly changing region, your best potential allies emerge, you can do nothing to support them. Sad for them - and disastrous for us all in the long-term, because our would-be allies will simply look elsewhere for help.
But of course there is one thing of which we can be certain. Though everything else in the world changes, Britain will still talk, and try to act, above its pay-grade in one arena.
Politicians from all parties, led by Prime Minister David Cameron and Foreign Secretary William Hague, will continue to fixate on pressuring Israel above any other state in the region. Since Israel is fast becoming the only country in the region with whom Britain has any sway, in one last grasp at global relevance, Britain's leaders will continue to push ever harder on Israel.
As everything else in the region falls apart into unpredictability, the one stable, democratic and truly liberal state in the region is the one state that will get lectures from the British. The Saudis can pimp their troops out to murder Bahrainis without a peep from the Foreign Office. But if one Jew in Jerusalem builds a conservatory on his house, the full force of Her Majesty's government's opprobrium will be brought down on his country.
Iran does not listen to us. Hamas does not listen to us. Syria, Egypt, Libya and Saudi do not listen to us. So we must insist Israel listens to us. Let us hope that, in this regard alone, Israel for once behaves like its neighbours.