What happens when the decision to kill is no longer made by a soldier, but by a machine?

Yesterday I attended an excellent pair of expert talks on Artificial Intelligence and Lethal Autonomous Weapons Systems (LAWS), organized by students in the Politics Department at The Catholic University of America. LAWS are weapons that use artificial intelligence to select and attack targets—drones, for example, that can hover until what they “recognize” as a target appears, and then strike.

As Politics chairperson Maryann Cusimano Love observed, the crucial question is: What does “human engagement” mean in this process? In just war thinking, a combatant may at times be obliged to kill. But in LAWS, human involvement grows ever more remote. A commander might be hundreds of miles away. Is “engagement” satisfied if a human can merely abort an AI-driven strike? Or does “engagement” demand an active, conscious choice to pull the trigger? In other words, is the decision to kill active or passive—by commission or omission?

The conflicts in Ukraine and Gaza show us how quickly these questions are moving from theory to battlefield reality. That is why I have regularly emphasized the need to speak to questions of modern warfare in the light of the just war tradition. I reiterate that because, in our time when the importance of our just war principles is downplayed in some quarters, some Christians seem to think that the only faithful response leads to functional pacifism. That is not so. Self-defense remains a right. The pressing question is not whether to fight, but how—and how to ensure that the human moral agent is never erased from the picture.

As Dr. Love stressed, weapons cannot bear responsibility. Only persons can. They possess conscience. They stand before God. We cannot cede this responsibility to machines in the name of “efficiency.” Last April’s monthly prayer intention captured this: We prayed that “the use of the new technologies will not replace human relationships.” That applies even in war, where the encounter with the enemy—tragic as it is—remains a human relationship.

This truth finds expression in Carl Foreman’s 1961 film, “The Guns of Navarone,” a very pro-life movie from its continuous grappling with questions of killing, even in the midst of war. One scene in particular speaks very powerfully to this dimension of humanity, even between combatants. The hardened fighter “Brown,” famous for his knife skills from the Spanish Civil War, hesitates to kill in close combat a German soldier who’s boarded their ship. When asked why, he replies: “You shoot a man at two hundred yards, he’s just a moving target. You kill him with a knife, you’re close enough to smell him.”

At that moment the enemy ceases to be a “target.” He is a man.

The cardinal principle of just war is never to lose sight of this truth. Even as enemy, the other is not a thing to be processed by a machine, but a person whose life must be reckoned with in full human conscience.