France and the entire world are still grappling with the shock and horror of the terrorist massacre that appears to have claimed close to 160 lives in Paris and left many more wounded. The first reaction among civilized people is solidarity, grief and condolences for the victims, their families and the nation as a whole–as well as righteous anger at those who perpetrated the crime.

But then the inevitable questions begin: how could this have happened again, and what do we do to stop it from happening next time?

The “how” is the most immediately pressing problem for policymakers in national security: how did all these attackers manage to coordinate the attack under the radar? How did they manage to acquire so much in the way of firepower and explosives without being caught? How can security measures be tightened to reduce the risk of another attack going undetected?

Beyond that, however, is the larger problem of why it happened and what can be done.

Those on the conservative right have quick, seductively easy answers: it’s all the fault of Islam, they say, loose immigrantion policy and perceived Western weakness. Conservatives will tell you that if we were only more belligerent in the Middle East, dropped more bombs and made the terrorists fear us more, that Westerners would be safer in our countries.

Serious people know those are the wrong answers. ISIL exists today directly because of George Bush and Dick Cheney’s ill-advised and immoral war in Iraq, followed up by an incompetent and short-sighted policy of de-Baathification that left Sunni Iraqis leaderless and oppressed by the new Shi’ite majority, which in turn made them easy prey to radicalization. We know that terrorism is now a decentralized activity: no longer is it necessary for radical groups to train terrorists at home and send them to the West. All they need do now is spread propaganda through social media and wait for the fruits of their evil to ripen domestically. And we know that use of military force not only fails to discourage terrorist activity, but in most cases actually strengthens and reinforces it by sowing chaos and hatred in those populations. The foreign policy prescriptions of American conservatives can rightly be dismissed as discredited, immoral and counterproductive jingoism.

But the left is found wanting as well. The immediate reaction from many on the left is to simply blame the problem on blowback, insisting that if Western powers simply stopped trying to exert influence on the Middle East, terrorism would not reach Western shores. Many liberals further argue that the social problems in most middle eastern countries suffering from extremist violence are the direct result of a history of imperialism and colonialism.

These are thornier arguments to dismiss, not only because they contain a great deal of truth, but also because unlike conservative claims that are testable and false, the blowback argument is unfalsifiable. If you look hard enough and go far enough back, you can make the claim that almost any problem in any developing country in the world is ultimately due to undue Western influence. For instance, Iran’s mullah problem can certainly be traced back to the CIA-backed coup against the democratically elected Mossadegh in the 1950s. But it’s also important to note that that was over 50 years ago now, and at a certain point even liberals need to start holding the people of Iran to account for their current government’s behavior. Similar examples could be proffered for almost anywhere in the world, including in Chile where America has blood on its hands for its involvement in the coup that led to the rise of the dictator Pinochet, but where that immoral intervention has not led to decades of Chilean anti-American terrorism.

And that’s the biggest weakness of the liberal foreign policy argument. It’s based on two separate fallacies: one of special pleading, and one of unfalsifiability. More importantly, it fails to provide us with a useful pathway forward.

The blowback from the misguided and immoral invasion of Iraq could take a century or more to sort itself out. At some level any violence perpetrated against the West as a result of it would be to a certain degree self-inflicted, but that doesn’t exactly help policymakers decide what to do now.

Right now there is an active group of murderous, barbaric theocratic cutthroats who adore violence, despise and rape women as a matter of official policy, desecrate and destroy monuments that have stood for thousands of years, and seek to establish a regional and global caliphate with the goal of a final battle against the Great Satan. That’s the reality. That group is engaged in two separate brutal, bloody civil wars (one in Iraq and one in Syria), and it is making incursions into other countries as well, including Egypt. It is also very good at social media propaganda, holds a large amount of territory, and foments terrorism and extremism beyond its immediate regional reach.

One could step back and remove all Western influence from the region, both in Syria and in Iraq. One could simply let the Shi’ites, Kurds, Syrian Assad loyalists and Syrian anti-Assad moderates (if any exist) battle it out themselves and hope that some combination of the above emerges victorious, trying not to draw any of their ire and taking in as many refugees from the war-ravaged conflict zones as possible. But it’s highly unlikely that the attacks against the West would stop, it’s likely that their propaganda would be increasingly successful at radicalizing young men in the West, and it’s certainly true that populations across Iraq, Syria and elsewhere in the Middle East would be greatly harmed by allowing ISIL to expand. Even if America and its allies immediately abandoned all conflict in the Middle East, terrorism would likely continue–and even 30 years from now the Glenn Greenwalds of the world would still say any such attacks were just so much blowback. Those outcomes and that ideology are not acceptable at a moral or a practical level.

Ultimately, what drives both domestic jingoist conservatism and ISIL’s brand of extremism is a commitment to violent aggression beyond its own borders, a weird fetishization of guns and gun violence, a misogynistic hatred of sexual freedom for women and non-traditional relationships of all kind, and a deep commitment to conservative religious fundamentalism and patriarchal gerontocracy as the organizational structures of society.

Whether it’s unprovoked Western violence against innocent people in the Middle East, or unprovoked Islamist violence against innocent people in the West, that’s what both sides have in common. That’s the common enemy.

The path forward cannot lie in reflexive hatred of Islam, or in reflexive attempts to avoid all blowback in an isolationist crouch.

It must lie, rather, in opposing violent conservative fundamentalist extremism both domestically and abroad, wherever and whenever it appears. Just how we go about doing that depends on the circumstances, of course, but that’s the goal we should always keep in mind.

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Follow David on Twitter @DavidOAtkins. David Atkins is a writer, activist and research professional living in Santa Barbara. He is a contributor to the Washington Monthly's Political Animal and president of The Pollux Group, a qualitative research firm.