I just put my 1-year-old to sleep. He went down easily. He doesn’t know it yet, and won’t understand it for years I suppose, but minutes before he fell asleep, White House sources revealed that President Trump intends to withdraw from the Paris climate agreement. The man who will probably be my son’s first image of what a leader looks like has chosen a short-sighted, confused, greedy version of the present, or of past greatness, over the future of the planet that my son and his friends, and their children, will inherit.

There’s no sense anymore in bothering to cite the scientists’ numbers or to reproduce charts or to quote from “Laudato Si’,” Pope Francis’ encyclical that Mr. Trump received from its author’s hands just a week ago. The debate is over, and it has long since ceased to be a real debate. Even the former ExxonMobil chief executive officer who is Mr. Trump’s secretary of state, Rex Tillerson, became the last, best hope that the president would opt to stick with the climate deal. Paris was never enough, but it was the one step that virtually every country on Earth could agree to start with. It stood for a rare, almost impossible hope that global consensus might be possible for a species otherwise embracing its own suicidal fragmentation.

Paris was never enough, but it was the one step that virtually every country on Earth could agree to start with.

“Suicide,” actually, isn’t the right word. My son isn’t choosing the planet he will be getting. The unborn children to come certainly aren’t. Nor are the vast majority of living, grown human beings. Mr. Trump’s fleshy shell will be rot and decomposure by the time the climate truly turns to chaos. This is war—the war of one generation on those that follow it, and we are led reluctantly into battle against our descendants by a despot determined to ignore the outcry of his scientists, his citizens and even his most oil-stained advisers. We need to call it what it is.

I don’t relish the prospect of war. I am one of those Catholics with serious reservations about our church’s “just war” teaching—about whether a war can ever be just. Our God is a Prince of Peace who bears no arms. But we need not affirm the justice of a war to recognize that it is happening. The Catechism of the Catholic Church defines an act of war more stringently, I think, than many who claim the banner of just war theory admit. It says, “The damage inflicted by the aggressor on the nation or community of nations must be lasting, grave, and certain.” That’s a high bar, but Mr. Trump is roaring far above it. This is what we are up against. This is it.

This is war—the war of one generation on those that follow it.

When such damage is underway, we cannot stand by or claim refuge in our complaints as we grudgingly take part. “Actions deliberately contrary to the law of nations and to its universal principles are crimes, as are the orders that command such actions,” the catechism continues. “One is morally bound to resist orders that command genocide.”

The command has gone out now: We are to proceed with the destruction of the planet, in the name of some imagined greatness of the past, to preserve the privileges of the most privileged country on Earth. We are to refuse coordination, cooperation, restraint and consensus. We are to deny our children, born and unborn, the planetary gift we received, from our parents and from our God. We cannot.

Once, in the West Bank, I attended a march, a Palestinian protest against Israeli soldiers involved in yet another land grab. At the front of the march were children, barely old enough to run ahead, carrying a flag and leading the chants—”Palestine will be free!” I asked a mother why the children go first. Isn’t it unsafe? Those soldiers have guns, and they are known to fire them on marches like this. She told me that the children go first because it is the fight for their future, more than anyone’s. They can’t put it off. They have to learn. This is their life, their survival.

I wished it didn’t have to be so, and I know she wished that more than I did, but that’s what occupation means. That is what it means to be at war.

By the time my son wakes up—from this nap today, or in a few years from his blessed innocence of world affairs—I hope the war will have ended without a shot. I hope it can be won for him with beautiful nonviolence, leaving behind stories that will help him grow up proud of his people. I hope we can love the enemy, as God commands us. But the war can’t be won without seeing it for what it is, and for what it now demands of us—the grown, the living.

Nathan Schneider is a professor of media studies at the University of Colorado Boulder. He is the author of Governable Spaces: Democratic Design for Online Life and God in Proof: The Story of a Search From the Ancients to the Internet.