Almost everyone seems to have an opinion about whether (pdf) or not to bomb ISIL*. Are they really all experts on the complexities of Syrian military and political affairs?

Maybe not. There's another possibility: overconfidence. We tend to exaggerate our knowledge and under-estimate uncertainty. Daniel Kahneman has called this the most damaging of cognitive biases. It seems pervasive in economics, so why shouldn't it also be found in military affairs? Dominic Johnson writes:

There is...one thing that is predictable about war: overconfidence. Even if the outcome of war cannot be known in advance, the historical record shows a remarkable empirical regularity in that politicians, military leaders, and the public on both sides tend to believe they will win, with astounding repetitiveness. Nations around the world and over the centuries have repeatedly underestimated their enemies, overestimated their own capabilities, and exaggerated their ability to control what are inherently unpredictable events.

In today's Times, Matthew Parris echoes this, claiming that those who expect the Free Syrian Army to mop up ISIL after bombing "haven't the foggiest" about its actual composition.

For me, this creates a presumption - a Bayesian prior - in favour of non-intervention. Simple heuristics (pdf) can be good solutions to complexity. "Don't take part in wars in the middle east" is one of these: one could argue that this heuristic would have served us well in Iraq and Libya**. This practical position is amplified by a moral one. As Alex says, we in the UK won't be the biggest losers if things go wrong - and one must tread carefully when imposing burdens on others.

It is also a case for having a free vote on the issue. Cognitive diversity can be a good way of coping with complexity. I prefer Labour's disunity to SNP's uniformity.

I should, of course, caveat this. This presumption against bombing could be overturned if we had a strong enough signal that bombing would work - for example, if there were a clear and present danger of ISIL conquering a city which could be prevented by attacks upon specific targets. And Hopi was right months ago - that non-intervention also has costs.

All of this is to agree with Freddy Gray: if you look at Corbyn's actual words, his policy seems reasonable.

Herein, though, lies a paradox. For me, the argument against military action is, structurally, the same as the argument for free markets - that interventions in complex systems of which we have limited knowledge can have unintended consequences. From this perspective, we'd expect an overlap between attitudes to military intervention and free markets, with free marketeers opposing bombing and economic statists favouring it. However, except for a few consistent libertarians (I'm thinking of the likes of Bryan Caplan) and a few Labour pro-bombers, this is not what we see.

I fear this might be due to an even more pernicious bias than overconfidence - tribalism. Nick Cohen alleges that Corbyn isn't so much anti-war as anti-west, and Matthew Parris says of the pro-interventionists: "The point is to join our allies in a fight. Never mind on which side, so long as we're all in it together."

This mix of bounded knowledge, overconfidence and tribalism makes me fear that whatever decision we take about Syria has a very high chance of being wrong.

* Strictly speaking, this sentence is an example of selection bias.

** I say this tentatively because we don't know the counterfactuals.