Here's the one weird old trick you need to identify someone who doesn't have a clue about Syria.
They talk about Libya.
Why? Because it feels like Libya is where we have been here before. It is where we have fought over and carried out air strikes, and where we have seen the progress of a country after a dictator's fall.
So while half the left use Libya as their reason not to engage with the crisis in Syria, half the right are citing Libya to explain why air strikes in Syria are the answer.
In this case, left and right both lead to wrong.
Libya doesn't tell us anything about Syria.
Libya and Syria are not the same place. They are not similar places or even on same continent.
Historically, strategically, geographically, politically, militarily... different.
And yet, every time we talk about Syria we end up talking about Libya.
How do I know?
Because in the course of my previous working life, I've spent a lot of time in both countries. I know my way around Tripoli. And Tripoli.
I was still working around both countries during the Arab Spring of 2011, when citizen protest movements in both Libya and Syria challenged un-elected leaders, and were brutally repressed. In both countries, repression turned to armed conflict, and in turn to civil war.
Let's start by looking at what happened in Libya.
The Gaddafi regime fell in weeks -- as it were always going to fall. Within three days of the start of anti-government protests, the opposition were in charge of the country's second capital, Benghazi. Six weeks and UN Security Council Resolution 1973 had been adopted, a no-fly zone was in place, and a coalition of 27 states from Europe and the Middle East sent in strikes against pro-government forces.
Six months after the start of protests and Tripoli fell. Gaddafi died, and Libya disintegrated into areas under control by separate more-or-less Islamist militias. And this is more-or-less where Libya remains.
Because Libya was never a cohesive country. It was, and is, barely a country at all but a scattering of six million people in a vast desert, with almost all of them concentrated in a thin coastal strip. The capital, Tripoli sits at the top left, the second city -- and virtually the second capital -- Benghazi, at the top right. With the exception of that coastal strip, the rest is sand, and one-Toyota towns.
During Gaddafi's day the powerful kept an occasional politic presence in Tripoli and dwelt in their tribal areas and in loathing. The moment they had the opportunity to go after Gaddafi, they went after him. Given the intensity of feeling, the three days to take Benghazi looks restrained.
There was no depth to the Libyan state. The only question was, would the regime have the chance to use their control of the air?
In vast empty desert spaces like Libya, it is control of the air that makes the difference. Air and the odd tank for street by street fighting -- Gaddafi would call that a government.
On the day that the UN debated air strikes, Gaddafi was sending tanks into Benghazi.
'It's over. The issue has been decided,' he said. 'We are coming tonight... We will find you in your closets... We will have no pity and no mercy.'
The UN recognised that without control of the air, Gaddafi's push was going nowhere and authorised air strikes. It signed off on, and supported, a no fly zone while Benghazi breathed, and Gaddafi was done.
And no, Libya's fate since has not been kind. It has descended into factionalism, and partition, and Islamism and the competing writs of governments. And now, by a natural process of humans, revisionism is taking hold.
The Arab Spring was happening. In Egypt and Tunisia governments blinked. Libyans had every right to protest, and once they had protested there was no mercy to be had from Gaddafi. He'd spent forty years proving that.
People say Libya under Gaddafi worked. It was a police state. It was a wretched grey murder-state with basic dental. I spent a lot of time there, and I saw hunger, and fear, and Mukhabarat, and those on the good days.
At the best of times, Gaddafi's regime was a stretched and grubby sticking plaster over a country that didn't work.
There was no Save the Dictator option, and neither should there have been.
The Libyan people deserved not to be hunted down 'like rats and cockroaches' in the meantime. Airstrikes -- and international intervention -- in Libya saved lives. They were a tool suited to a purpose, stopping immediate deaths in the civilian population.
What happened afterwards is not an argument not to have intervened. Neither is what happened afterwards the result of the strikes. Just because B follows A doesn't mean B is the result of A.
We call that the post hoc fallacy or occasionally the perfectly bloody obvious fallacy.
So how does all of this differ from what is happening in Syria?
First, geographically. Libya and Syria are very different. Syria is much smaller, tighter country. It too has a coastal strip, but dense packed; the fighting more town-to-town and house-to-house than city-state against city-state.
Assad still has some support in every city, and he has people who fight for him -- the Christian communities of Aleppo for example, who have so much to fear from ISIS.
It is this tightness, this complexity that explains why conflict in Syria has lasted four years, and will likely last another ten. And unlike in Libya, the situation is unlikely to develop beyond Assad.
There is no dacha on Lake Balaton for Assad. There is no way out. Hell, there was a huge argument about picking him in the first place. He was only allowed to inherit because the Generals agreed he was uninspiring but there was no-one else.
They are not going to let him go now.
There is no deposition strategy for Assad. While Gaddafi lived in palaces, the Assads always lived in and amongst civilians. They are rooted in civilian areas and they have never been separated from their support. The heart of the regime is the heart of Damascus.
There is no easy solution based on a no fly zone, and no alternative to the bloody ground war that is emerging.
Now you can argue, and argue legitimately, that after Gaddafi's death the international community should have moved in to Libya. We should have done more, spent more and saved more. The flow of refugees and of bodies washing up on Libya's shores might have been a little stemmed.
And you can argue separately that Assad is going nowhere, and it's hard for a dictator to stick around after killing half of Hama, and so that any solution for Syria will include a lifetime's policing and a lifetime's aid.
What you can't do is argue that any plan for Syria can be built on that used in Libya, or that conflict in Libya can be used be used to prohibit engagement with Syria.
So stop it already.