In the aftermath of attacks like the one in Paris on Friday, which killed 129 and critically wounded nearly as many, two sets of questions tend to arise: How could this happen? And why did it happen?

The “how” questions are what preoccupy investigators for the first few days after such an attack, as they race to identify the assailants and their collaborators before they can strike again. A complex assault such as the Paris operation usually involves many more people than the perpetrators; as of this writing, seven known assailants have been killed, but authorities in France and Belgium, where the attacks are believed to have been organized, are hunting for additional suspects. Officials will also be looking for weaknesses in France’s defenses. How could so many attackers with explosives have penetrated the country? Clearly there was a major intelligence failure. Border security, surveillance capacity, and coordination between security services will be heavily scrutinized.

The next set of “how” questions will be more difficult to answer. The Islamic State took credit for the attacks, and no other group has yet made a counterclaim. But if the ISIS claim proves to be true, how exactly was the Islamic State’s central leadership involved? The scenarios range from the ISIS high command training the attackers and facilitating the attacks themselves to a relatively autonomous group of ISIS loyalists conducting the attacks largely on their own. There are multiple possibilities in between as well; for example, an Islamic State operative could have been charged with organizing attacks in Europe without having to check in with headquarters. The answer is important because it will give clues about whether the Islamic State intends to devote its considerable wealth and military expertise to foreign operations, which would be very worrisome. It is worrisome enough if those affiliated with or merely inspired by the Islamic State organized such sophisticated attacks.

But the most difficult question is also the most consequential, and it concerns not how but why the attacks took place. Again, there are a range of theories, some of which could overlap, some of them mutually contradictory:

1. This is what global jihadists do—they can’t help themselves.

2. This was always the plan, but ISIS didn’t have the capability or opportunity to carry it out before.

3. The Islamic State wants to offset its territorial loses in Syria and Iraq by carrying out high-profile attacks abroad.

4. It wants to show up al-Qaeda to cement its position as leader of the global jihad.

5. It wants to deter powerful nations from carrying out more attacks against it.

6. Quite the opposite: It actually wants its enemies to go all in in Syria and Iraq in order to a) drain their resources, b) create total chaos, c) present itself as defender of the Muslims, and/or d) bring on the End of Days.

The truth is, we probably won’t know the answer for sure for some time. It took years for the real reasons why al-Qaeda attacked the United States on 9/11 to surface, from computers recovered in an al-Qaeda office in Kabul—the group hoped the United States would either pull its troops entirely out of the Muslim world, or commit to a massive invasion that would drain America’s treasury and enrage Muslim opinion, in turn eventually forcing America to leave the Muslim world anyway.

Initially, the United States didn’t do either. Instead, it toppled the Taliban government that had allowed al-Qaeda to operate in Afghanistan, and drove al-Qaeda from its hideouts there by supporting the Taliban’s enemies from the air and with special-operations forces. But soon after that, the United States sent large armies into Afghanistan and Iraq. Had the American people known that’s what al-Qaeda wanted all along, perhaps they would have demanded a different course.

Which brings us to the response to the Paris attacks. French President Francois Hollande has pledged a “pitiless” retaliation. France was already bombing the Islamic State in Syria as part of the American-led coalition against the group, so he presumably intends to escalate France’s military role, with France’s weekend airstrikes on the Islamic State headquarters of Raqqa perhaps representing a first step. Maybe he will go so far as to invoke Article 5 of the North Atlantic Treaty, according to which an attack on one NATO ally is an attack on all of them, to call for an allied invasion of Islamic State territory. Even if Hollande doesn’t want to go that far, the political pressure to do more to fight ISIS will be immense. And indeed, terrorism is designed to provoke an overreaction—either complete disengagement or a massive show of force.

But if the Islamic State struck France to persuade the allies to change the middle course they’ve been pursuing between those two extremes in Syria and Iraq—a course that involves airstrikes and empowering local militias—then perhaps it’s worth considering the merits of the approach the Islamic State apparently dislikes so much. Over the past year, the allies have chipped away at the Islamic State, reducing ISIS territory by 25 percent, according to the U.S. Defense Department. The pace is slow but steady.

Still, even the destruction of the Islamic State’s government in Syria and Iraq won’t immediately end the group’s terror attacks abroad. If anything, it will increase them. Terror campaigns are used by weak states that feel threatened. There are other countries where ISIS’s leaders or their affiliates can plot attacks. That’s not a reason to escalate in those countries too; it’s merely a recognition that the problem extends beyond the Islamic State’s core territory.

ISIS promised that the Paris attacks were “the first of the downpour.” Given the political instability in the Middle East and North Africa that has fueled the rise of the Islamic State, the countries on its enemies list will likely be weathering the storm for a long time to come. But the best way to do this is to find out why it’s raining in the first place, and how best to find shelter.