In the interests of taste and decency, let us look away from the gruesome spectacle of the civil war that has engulfed the Labour party and concentrate instead on the far more serious conflict in Syria. So here are some questions that you might like to ask yourself (with my answers) before you decide whether you agree with David Cameron that the UK should now join the international military action against IS in Syria.
1. Is IS a direct threat to the UK? My answer: Yes. What happened in Paris two weeks ago could happen here tomorrow. Several hundred British citizens are believed to have gone to Syria to join IS; according to Mr Cameron, about half of them have returned. The PM also says that over the past 12 months, police and security services have disrupted seven terrorist plots "either linked to ISIL, or inspired by ISIL's propaganda".
2. So won't joining the military action against IS make the UK even more of a target and increase the threat to British citizens? My answer: No. The UK is already a prime target.
3. Will it make the UK safer? My answer: Possibly, if it discourages young Muslims from travelling to Syria to join IS, and if it forces the group's leaders to scatter, making it more difficult for them to coordinate attacks. Cutting their supply lines and hitting the oil facilities they have captured could have an effect. It could also have little or no effect.
4. Is IS a threat to the region and therefore an indirect threat to the rest of the world? My answer: Yes. In the words of UN security council resolution 2249, passed unanimously a week ago: "The Islamic State in Iraq and the Levant constitutes a global and unprecedented threat to international peace and security." The resolution called on all UN member states "to use all necessary measures to prevent and suppress terrorist acts committed specifically by ISIL and to eradicate the safe haven they have established over significant parts of Iraq and Syria."
5. Can IS be defeated militarily? My answer: No. As experience in Afghanistan has amply demonstrated, defeating a terrorist group by military means is an impossibility. The US-led air campaign against IS in Syria has already conducted more than 2,500 attacks, with relatively little to show for it. Mr Cameron acknowledged as much in his 36-page response to the House of Commons Foreign Affairs select committee: "The objective of our counter-ISIL campaign is to degrade ISIL’s capabilities so that it no longer presents a significant … threat." Note the operative word: "degrade", rather than "defeat" or "destroy".
6. So at what point would any UK military action cease? My answer: That's a very good question. The implication in Mr Cameron's statement is that a campaign of air attacks would lead to an accelerated political process in which "moderate" opposition groups would be strengthened and President Bashar al-Assad would be encouraged to step down as part of a transition to a more democratic Syria. That seems a huge leap of faith.
7. Isn't there a real risk that the UK would do more harm than good by joining the military campaign? My answer: I doubt it. UK involvement is unlikely to be a game-changer, despite the prime minister's claim that the UK has "world-leading military capabilities to contribute, which many other countries do not possess."
8. What is the strongest reason for UK joining the military action? My answer: It would demonstrate that we remain part of a global community that has come together in a way not seen since the international action against Saddam Hussein following the Iraqi invasion of Kuwait in 1990. A coalition that includes the US, Russia, France, Jordan, Saudi Arabia and Turkey cannot easily be dismissed as simply a rerun of the US-led coalition against Saddam in 2003. And to ignore a direct appeal from France, our closest European neighbour, would inevitably be seen as turning our backs on a neighbour in need.
9. What is the strongest reason against the UK joining? My answer: I recognise that our experience in Afghanistan, Iraq and Libya, where we bombed the bad guys only to find that more bad guys emerged from the rubble, is not exactly encouraging. On the other hand, military interventions in Bosnia, Kosovo and Sierra Leone did have positive outcomes.
10. Why should we believe anything that Cameron says, given that it's presumably based on extensive briefings from the security services, who were so catastrophically wrong about Iraq in 2003? My answer: because this time, unlike when the debate was about whether Saddam was developing weapons of mass destruction, no one is arguing that IS is not a real threat or doesn't really exist. The only debate is over how best to confront the threat.
So how would I vote if I were an MP? I'd vote Yes -- but with a very heavy heart.