Why, for the second time in less than a year, has Paris been hit with a mass casualty attack by Islamist terrorists? Is France uniquely vulnerable to these attacks?

And is there anything Australians can learn from the Charlie Hebdo shootings and the atrocities on the weekend that have so far killed 129?

Like Australia, France is a multicultural country, but it does multiculturalism in quite a different way from Australia.

At the heart of its democracy is "laicite" – an extreme form of secularism that Deakin University academic Greg Barton described as "a bit silly".

The policy makes it difficult to measure how many Muslims live in France, because no data is allowed to be collected on ethnicity and religion. But there are estimated to be about 5 million Muslims living there, or 7.5 per cent of the population, the largest Muslim population in Europe.

Many Muslims came to France from its former African colonies and live in generational poverty in high-rise housing estates on the edges of the big French cities.

The unemployment rate in these areas is 30 per cent or more among young people. According to Barton, discrimination in job-seeking against people with Muslim names is entrenched in France, to the point where many change their names to get a foot in the door.

Despite their relatively small proportion of the population, at least half the people in France's prisons are Muslim and the Charlie Hebdo attacks revealed that jails were factories for radicalisation.

And, while Australia rejected attempts by its far right to ban the burqa, France did just that, as well as preventing any other public religious expression in the government, judiciary or schools.

Integration is difficult to define and measure, but a recent survey suggested that only 75 per cent of French Muslims "feel French", and the more devout they are religiously, the less they identify with the state.

France also attracts the ire of the militant Islamists with its deployment of more than 10,000 troops in West Africa, Central Africa and Iraq, as well as an aircraft carrier to take on Islamic State.

Combine it with porous borders and the easy access to weapons that flow across them, and France is particularly vulnerable to terrorist attacks.

Australia, while it's involved in foreign wars, does better on the home front: "It's more laconic" about its divisions, "which is a strength," according to Barton.

However, there is no reason for Australians to feel complacent

"Our rates of radicalisation are the same as France's," Barton says.

Between 1500 and 2000 French Muslims are believed to have gone to fight in Iraq or Syria.

Australia has contributed about the same proportion of its Muslim population – perhaps 200 fighters.

"We don't understand the process of radicalisation as well as we need to," Barton says.

"We've got to keep on doing what we do well – our social cohesion and multiculturalism are working, and are success stories. But there is something to do with the way ISIS sets up social networks and recruits people."

Young Australian Muslims, like their French counterparts, are going online and "getting lost in a feedback loop of dodgy information and emotive reporting".

We do not yet know how to bump them out of it. "It's not so much that we're losing the war of ideas, it's that we don't try hard enough to win it," Barton says.

"Moderate Muslims need their capacity built and we don't do it as well as we could. Meanwhile Islamic State is working hard to build their capacity, with some success."