OK, I’m all out of ideas when it comes to Syria. In the wake of last week’s decision by the United States to send arms to the Syrian opposition, there’s been unending debate about the pros and cons of foreign intervention. But it doesn’t seem to have got us anywhere.

The G8 leaders, meeting in Northern Ireland at the weekend, backed the holding of a peace conference “as soon as possible,” saying that they “remain committed to achieving a political solution to the crisis based on a vision for a united, inclusive and democratic Syria.” But anything more specific was blocked by the impossibility of reaching agreement between Russia on one hand and Britain, France and the US on the other.

Opponents of intervention have a habit of asserting – quite correctly – that intervention is dangerous and peace talks are the answer, without offering any alternative strategy for how peace talks are to be initiated and brought to a successful conclusion. Boris Johnson, for example, says that “This is the moment for a total ceasefire, an end to the madness. It is time for the US, Russia, the EU, Turkey, Iran, Saudi and all the players to convene an intergovernmental conference to try to halt the carnage.”

Well yes, of course. But if they don’t, then what happens? I much prefer the honesty of Juan Cole, who also opposes intervention but admits his despair at the alternatives: “I wish there were a way for the international community to stop this carnage, but I feel helpless, I just don’t see a way.”

With about 100,000 killed so far, the pressure to “do something” about Syria is understandable. But the flip side of those who want peace without a plan to get there is those who want intervention without a clear picture of how it would help. And as someone pointed out last week (it might have been Cole; I can’t find the reference), the Algerian civil war in the 1990s killed a similar number and nobody in the west seemed impelled to intervene.

For the case in favor of intervention, see General Wesley Clark, a former NATO commander and former presidential candidate, writing in the New York Times on Tuesday. He argues that the west needs to show the will to escalate the conflict if necessary in order to bring the Assad regime to the negotiating table. The point is not to achieve military victory, but to change the calculations of the other parties so that they are willing to come to terms.

Is he right? Three weeks ago I put it like this: “Foreign intervention in civil wars is a dangerous game; nonetheless, in some cases it’s the least bad option available. Unfortunately there’s no way of telling in advance whether this is one of them.”

Greater internationalisation of the conflict might be a step forward. The US and Russia are clearly much closer to each other in their objectives than are Assad and his opponents; as they become more involved they have both the incentive to try to impose peace on the combatants and the leverage to make it stick. But the short-term costs are steep, while the long-term benefit remains uncertain.

As is often the case in war, the shape of the expected outcome is reasonably clear. Clark expresses it well:

The formula for diplomacy is clear: a cease-fire agreement; a United Nations presence; departure of foreign fighters; disarmament of Syrian fighters; international supervision of Syria’s military; a peaceful exit for Mr. Assad, his family and key supporters; a transitional government; and plans for a new Syria.

The question is how to get there. Clark’s option of increased US involvement might work – I don’t think there’s any basis on which we can say for sure that it wouldn’t. But it might also be a disaster.