The British artist Damien Hirst once referred to the 2001 attack on New York's World Trade Centre as "kind of an artwork in its own right. It was wicked, but it was devised in this way for this kind of impact. It was devised visually".
Now, 13 years later, Western governments, while able to describe in strategic terms the threat of the Islamic State in Iraq and Syria (ISIS) to the Middle East, are still struggling to come to terms with its visual assault in the global media.
Like Osama bin Laden and Al-Qaeda, ISIS appears to understand the impact that lurid images of violence can have on the public imagination.
The irony, of course, is that the Islamic State's exploitation of images of "pornographic" violence is at odds with the Islamists' own condemnations of visual stimulation in other areas of life.
Indeed, their videos take sensory titillation to its limit.
Like an algorithm designed to access an adversary's digital network, ISIS' carefully staged videos, featuring the beheadings of American and British journalists and aid workers, have penetrated the Western psyche.
That psyche has long been primed to receive shocking imagery. Now, the electronic media's weakness for graphic violence has become ISIS' strength.
The visual politics of terror may seem primitive, but its practice can be as sophisticated as its effects are profound.
Like ancient conquerors who erected new temples on the sites where the vanquished had their own, the destroyers of New York's Twin Towers used visual terror to strike at the heart of their enemy's value system.
That is what terror aims to do: destabilise the foe's normative reality. Once the security of the familiar world is challenged, and its inner sanctums have been invaded and shaken, a space may be cleared for occupation.
Consider, for example, how Indonesia's Suharto regime, from 1966 to 1998, depicted alleged communist insurgent savagery, and compelled citizens to watch it on television and in theatres. The horrifying images were intended to foment terror. In the face of a grotesquely violent enemy, an even more terrifying state apparatus of organised violence emerged.
In effect, Suharto's visual politics of atrocity and terror created a new reality from the violence and terror associated with the demise of the old.
The same perverse logic is at work in ISIS' viral spectacles.
Though the need to confront evil remains as pressing as ever, Western societies' motivation for doing so may lose clarity.
After all, it is one thing to deliberate on the pros and cons of confronting external forces of irrational violence; it is something else to lash out against the producers of brutal, politically charged and upsetting imagery.
We must therefore ask ourselves what exactly is driving our response to the threats that ISIS presents.
Distinguishing between information about real national security concerns and images strategically designed to shock and titillate us will not be easy. But given the stakes, it is undoubtedly worthwhile.
The visual politics of atrocity and terror is only as strong as we imagine it.
That is why exorcising its demons will require more than military might.
It also will require us to think deeply about the strategic use of violent images in the digital age.
The writer is professor of law and director of the Visual Persuasion Project at New York Law School.