David Brooks(Josh Haner/The New York Times)

Like everyone, I was revolted by the beheadings of the American journalists James Foley and Steven Sotloff. It wasn’t just that they had been killed — though that is horrendous enough — it was the monstrous way the deed was done.

I’ve been trying to understand why the act of beheading arouses this strong visceral response. Why does separating a head with a knife feel different from a shooting or a bombing? Does this reaction contain some hidden intuitive wisdom, or is it just a blind prejudice?

First, a beheading feels different because it reveals something about the minds of the killers. By going beneath even the minimal standards of modern civilization, the militants of the Islamic State group get to show contempt for us and our morality. They get to deny the slightest acknowledgment of our common humanity. The purpose of terrorism is to terrorize, and the Islamic State means to show violence unbounded; the Islamic State will get inside our heads in the darkest way.

Second, a beheading reminds us of something disturbing in ourselves. We want to watch, and we don’t want to watch. Because of some warp in human nature, millions of people will go online to watch a beheading video though they might not even read about a simple shooting.

But the revulsion aroused by beheading is mostly a moral revulsion. A beheading feels like a defilement. It’s not just an injury or a crime. It is an indignity. A beheading is more like rape, castration or cannibalism. It is a defacement of something sacred that should be inviolable.

But what is this sacred thing that is being violated?

Well, the human body is sacred. Most of us understand, even if we don’t think about it, or have a vocabulary to talk about it these days, that the human body is not just a piece of meat or a bunch of neurons and cells. The human body has a different moral status than a cow’s body or a piece of broccoli.

We’re repulsed by a beheading because the body has a spiritual essence. The human head and body don’t just live and pass along genes. They paint, make ethical judgments, savor the beauty of a sunset and experience the transcendent. The body is material but surpasses the material. It’s spiritualized matter.

This infusion of the spiritual and the material is mysterious. Some Jews use the concept of tzimtzum, or “contraction,” to describe the mixing of the finite and the infinite. Christians have the larger concept of incarnation. Most of us, religious or secular, have some instinctive sense that there is a ghost infused in the machine.

Because we have this instinctive sense, we feel elevated when we see behavior that fuses the physical and spiritual. We feel elevated when sex is not only physical pleasure but also communication and spiritual union. We feel elevated when we read about the Jewish rituals of tahara, when members of a synagogue tenderly wash the body of a congregant who has died. We feel repulsed when the body’s spiritual nature is gratuitously and intentionally insulted.

Our revulsion makes us different from the religious zealots who are prone to commit or celebrate acts such as beheadings. The zealots often hew to a fringe of their faith that holds that the spirit and the body are at war with each other.

If the Islamic State is to be stopped, there will probably have to be some sort of political and military coalition. But, ultimately, the Islamists are a spiritual movement that will have to be surmounted by a superior version of Islam.

The truest version of each Abrahamic faith revels in the genuine goodness of creation. These are faiths that love the material world, especially the body. They’re faiths that understand that the high and the low yearn for each other, and that every human body has some piece of the eternal, even if you’re fighting against him.

— David Brooks is a columnist for The New York Times. John Costa’s column will return.