Another line crossed. With his threat to destroy cultural sites in Iran if that country retaliates for the killing of one its top military leaders, the president of the United States has told the world that everything is on the table, including the deliberate targeting of things that bear in them the accumulated emotion and artistry of centuries, things that are invaluable and can never be replaced. And it’s not just a line determined by international law or conventions on the preservation of culture. It is about the soul of a culture or a people, their inmost essence, their fundamental values.

When I read President Trump’s words, I went to my bookshelf and pulled out a volume I’ve owned since I was a boy, a history of world architecture, full of places that I still long to visit. And I wondered, what place will we hit first? Will my country lay waste to the great mosques and bridges of Isfahan and the remains of Persepolis? Will we destroy the last stones of the Achaemenid and Sasanian empires? If we are to be a barbarian nation, what are our new limits? Do we have any?

In March 2001, the Taliban regime in Afghanistan began to dynamite the 6th-century statues of Buddha in Bamian. The decision was both impetuous and brutal, in part an exercise in fundamentalist iconoclasm, in part an act of defiance and rage against the world at large. It was a galvanizing moment in the recent history of cultural heritage, which seemed at the time to be moving to a new international consensus: that culture was precious and that in some essential way, it was a common possession, a common value held across political, religious and cultural divides. Cultural heritage implied a global sense of “ours,” a need for collective stewardship that transcended ordinary divisions and boundaries. There was a nascent sense of mutual care for culture that wasn’t based on mere ownership.

The international response was indeed collective, a near-universal eruption of outrage and dismay at the loss. At the United Nations, after the Taliban announced its intent to destroy the statues, representatives of countries from around the world, Muslim and Christian alike, spoke of the Taliban’s intent as barbaric, and condemned the threatened vandalism. After the deed was done, and the ancient statues were reduced to rubble, the event defined the Taliban as an outlaw regime, uncivilized and evil. The fundamentalist religious government had committed countless outrages against its own people, especially women, but the destruction of the statues at Bamian created a monumental symbol of its barbarism that was somehow more tangible, more communicable, more purely distilled than its myriad acts of interpersonal cruelty. Fourteen years later, the Islamic State’s destruction at Palmyra did much the same work of branding, defining the cruel so-called caliphate as an organization beyond all bounds.

The very word barbarism is rife with danger. It seems to have emerged in ancient Greek as an ideophone, a word that expressed what the Greeks heard when they listened to someone speaking a language that wasn’t Greek: bar-bar-bar. But it has roots in other languages, too, and its dark side is built into the definition — one of exclusion, or otherness. Barbarians were, by definition, anyone who wasn’t Greek, or in later usage, Roman. They were uncivilized.

Over time, the word has come to mean uncivilized in a way distinct from merely “people who are not like us.” It means such acts as killing doctors, bombing hospitals, targeting children, the sick and the elderly, and destroying cultural sites. For decades, the United States has helped lead the evolution of the word to include the barbaric destruction of art, architecture, libraries and archives, and places of spiritual or historical significance. Our leadership has been imperfect and sometimes hypocritical. But when a lack of U.S. leadership led to the looting of Baghdad’s antiquities museum during the 2003 Gulf War, the U.S. response wasn’t to claim a basic right to destroy culture. We argued the “fog of war.” It was defensive, muddled and wrong, but not amoral.

Now our president has declared that cultural destruction is our right. Likely, it is a test, to see how far he can transgress the old boundary lines between civilized and barbaric behavior. He was elected after embracing torture, which was once thought to be across the line, in the dark zone. In his tweets on Sunday, he added the wanton destruction of culture to the list, too.

The odd thing is that the United States has been moving toward a more holistic understanding of the need to preserve and protect culture. In 2018, as part of the military budget, Congress created the position of coordinator for cultural heritage protection. A statement Sunday decrying Trump’s words, signed by cultural heritage experts in anthropology, archaeology and the museum world, details recent progress during the Trump administration, including the Smithsonian Institution’s plans to assist the Army in training a new corps of “monuments men,” experts who can help the military avoid cultural destruction.

That progress was inevitable, so long as the United States was trending in the same direction as other nations, toward a gathering sense of cultural possession and mutual understanding. To put it in terms the ancient Greeks might have used, our “polis” was getting ever larger, the sense of the city that defined “us” against barbarism was becoming more inclusive, capacious and diverse.

Some in our tormented land see that as a dangerous trend. It might lead to collective action on climate change or sexual violence or human trafficking. It might lead to cooperation across borders. It might lead to more reflexive outrage at things that were once upon a time on the other side of that line between barbarism and civilization, not just when they happen in such seemingly faraway places as Bamian, but at home, too. It might eventually extend that line to include violence against all defenseless things, including the destruction of landscape and wildlife habitat.

One of the fundamental problems with the old idea of barbarism is that it defined everything that was “other” as unknowable and unworthy to be known. It was self-satisfied and smug. In fact, there was always culture on both sides of this imaginary dividing line. The new line, the one we crossed this weekend, isn’t between one set of cultural values vs. another; it isn’t between people who speak our language and those who speak all others. It is between culture and the void, between the many and variegated ways in which different people try to live together peacefully and productively, and the pure nihilism of autocracy.

The threat wasn’t to Iranian cultural sites. It was to culture.