When going to war, however, with the resolve of killing people for a moral purpose, the default position should be against, so morality insists that the case for is resoundingly made. Mr Benn set out that case on BBC 5 Live this morning (here, about 2 hours 28 minutes in) in the following terms.
- There is a civil war in Syria in which millions are displaced. Isil is thriving in the resulting vacuum;
- There is a clear threat from Isil to our citizens, those of other countries and those living in the regions it occupies;
- There has been a unanimous UN resolution urging member state to do something about this;
- Attacks on the beach in Tunisia, in Ankara and Beirut, on the Russian plane in Egypt and most recently in Paris show the nature of this threat;
- The Paris attack could as easily have happened in Britain;
- Britain is already involved in a bombing campaign in Iraq;
- The Kurds say that support from the air makes a difference;
- France has asked Britain to join in;
- Backing off in fear is not the right thing to do;
- Innocents are already dying, and there is no option that does not involve this continuing;
- Isil are responsible for beheadings and crucifixions, throwing gay men off buildings and the sexual enslavement of women.
In response to that latter point, Benn falls back on points 9 and 10. Bombing Syria may increase the threat level on Britain's streets, but people are dying whatever happens, and backing off in fear is not the right approach.
That is not an argument one way or the other. The fact that people are already dying could support the case for intervention if it was more than likely that the number of deaths would reduce over time. The evidence for this is flimsy at best, and the precedents are not encouraging. Backing off, on the other hand, is generally a good idea if you think you are going to experience more harm than good. Whether you call it fear or pragmatism is a question of language.
The position of the Kurds in all this is unclear. Commentators have pointed out that they are much more interested in securing their own area that in taking on Isil outside it. That the French government should encourage Britain to join the bombing in Syria is understandable but does not strengthen the case. People who have just experienced an appalling tragedy do not always offer the most clear-headed advice.
Which leaves us with point 11. Isil represents a direct, ideological challenge to the humanitarian principles that underpin the western democracies - principles that run through the institutions of global governance that the western democracies were instrumental in creating.
This is also a statement of fact. But as an argument for war it falls into the “something must be done” category that allowed Tony Blair to lead Britain into the war in Iraq. Blair still points to Saddam's many cruelties as the reason why he finds it “hard to apologise for removing” him. Isil's cruelties are far more explicit, deliberately calculated to shock and posted on the internet.
Illiberal social attitudes and cruel punishments, however, do not qualify as a casus belli. Homosexuality may be punishable by death in 10 countries, mostly in the middle east, which Britain is not considering bombing. Nor is it bombing countries (some in Europe) in which women are trafficked into sexual slavery. Beheading and crucifixion exist as forms of capital punishment in a handful of states; indeed, a teenager remains under sentence of crucifixion in Saudi Arabia for participating in a pro-democracy demonstration.
Meanwhile, Assad's barrel bombs are killing far more people indiscriminately than Isil's more focused spectacles will ever do. As for the disparate, western-backed Syrian groups, their objectives beyond getting rid of Assad are unclear but it seems unlikely that secular western issues such as rights of gender and sexual orientation, of even the establishment of democratic rights leading to elections they can lose, are high on the agenda.
Another place, another time-frame. In 25 years Britain moved from Section 28 to gay marriage. Only 200 years ago it still used the pillory - a punishment similar to stoning. History is an erratic process. Attitudes change as societies open up, and as economic, social and educational prosperity spread, but this happens differently in different places. It is legitimate to be appalled by barbaric practices from which ones own society has moved on, but it does not follow that one can bomb others into change.