What is ISIS? What do its members want? What makes them tick?

These sound like basic questions. But it turns out that surprisingly few people have been trying to answer them — including, very scarily, within the U.S. government. And the White House's inability to understand ISIS and its ideology has severely hobbled the West's efforts to fight ISIS.

The celebrated reporter Graeme Wood, on the other hand, has tried very hard to answer these questions, in one of the most important stories to be written on ISIS. (Wood had already done impressive reporting on extreme Islamists.) ISIS, as it turns out, is motivated by a specific interpretation of Islam. And understanding the beliefs of ISIS's members helps to explain — and even predict — their actions.

For example, the main difference between ISIS and al Qaeda is not primarily over tactics or a clash of personalities, as we're often told, but over theology. Both ISIS and al Qaeda believe in apocalyptic end-times where an Islamic caliphate will face off against the forces of Christianity in an ultimate war. But while al Qaeda believes this time to be far off into the future, ISIS believes it is now. This is not an idle difference. This apocalyptic scenario requires the establishment of a new Islamic caliphate, and ISIS has been working to accomplish precisely this, seizing and holding onto territory instead of working as a decentralized underground network like al Qaeda. The centrality of the vision of the caliphate in ISIS's worldview suggests that the group will act in ways that are different from al Qaeda — and can be predicted.

Our lack of understanding of ISIS has led to epic bungling and needless death. The White House tried to have hostage Peter Kassig freed by using al Qaeda ideologue Abu Muhammad al Maqdisi as a go-between. This was doomed from the start, and not only because of the theological differences between al Qaeda and ISIS (al Qaeda views hostages as pawns in a power game, who can be useful alive or dead depending on circumstances, whereas ISIS views executing hostages as fulfilling a divine mandate to establish its legitimacy as a caliphate). This move also probably expedited the death of Kassig, who was beheaded. But it would have been worse if the White House had succeeded in its effort. It would have meant a rapprochement between ISIS and al Qaeda, a prospect that should give any sane person nightmares.

Now, why are our policymakers so blind about ISIS?

Most of my fellow conservatives have flagged a simple answer: political correctness. Political correctness dictates that "Islam is a religion of peace" and, therefore, if there are Islamic terrorists they cannot be motivated by Islam and must be motivated by something else. That something else can only be sheer insanity. And insane people, by definition, are illogical. (ISIS's logic is, of course, in some sense, "insane" — but it is still a logic, one that can be comprehended and has internal consistency, unlike sheer insanity.)

At his trial, the Islamist murderer of Theo van Gogh had to explain: "You should know that I acted out of my own conviction and not because I hated your son for being Dutch or for having offended me as a Moroccan. [...] I acted on the basis of my belief." People had tried to come up with all sorts of explanations for his behavior — instead of the obvious one.

But, of course, the problem is deeper than political correctness. For progressives, it's something I've come to call Vulgar Marxism.

While most progressives today disavow actual communism, those that care about the history of ideas still typically regard Karl Marx as an important and serious thinker. And his idea that has had the most influence is dialectical materialism, or the idea that the only driver of history is socioeconomic forces.

According to this view, religions, philosophies, ideologies, worldviews, and even culture at large are simply illusions, embraced after the fact to justify this or that move in our class warfare. Marx's views of history were influenced by 19th-century evolutionism. Think of the idea that we're just genes trying to reproduce: You may think that you're in love, or that you do your work for some higher purpose, but really it's just your genes tricking you into thinking that to increase their odds of spreading. Hence, for example, his notion that religion is just "the opium of the people" (a quote that is much kinder to religious believers in its context than is usually thought, by the way): beliefs have no influence on history.

This is why progressives view redistribution as almost a holy duty: If everything is about dollars and cents, well, everything is about dollars and cents. Conservatives also believe everyone should have a good standard of living, but they also believe that if people achieve this through work they will attain a greater degree of human flourishing than if they just get a check in the mail, since people's flourishing is not just limited to the material. That's why we have more nuanced views about redistribution.

Human beings are human beings — we are not just animals. We do not just want to feed and reproduce. We actually have beliefs and we actually make choices on the basis of those beliefs.

It's kind of crazy to have to point this out. We were made with an orientation toward ultimate truth, goodness, and beauty, and we seek it however we understand it — and how we understand it determines our actions.

The historian N.T. Wright talks about a worldview being like a set of glasses: not something you look at but something you look through; something that you don't think about — until there's a problem with it. Almost no progressive will make an explicit argument for Vulgar Marxism, but it's hovering in the background of much of their writing on almost every issue. And, in the case of ISIS, this mistaken worldview has almost certainly led to more bloodshed than there would have been had the progressives in the Obama White House actually tried to understand what ISIS believed, and why.