Pope Leo XIV Releases AI Encyclical, Warns of Autonomous Weapons
3 min readPope Leo XIV today released Magnifica Humanitas, his first encyclical and the first major papal document devoted entirely to artificial intelligence. Presented at the Vatican on May 25, the 43,000-word letter calls for binding global limits on AI in warfare and pushes back against what the pope describes as a dangerous concentration of AI power in the hands of a few.
A Pope Who Showed Up to His Own Launch
Leo XIV, the first American pope, broke with tradition by personally presenting the encyclical alongside Curial cardinals, theologians, and Christopher Olah, the Anthropic co-founder who leads the company’s interpretability research. Popes rarely attend the public release of their own encyclicals, and Vatican observers read the appearance as a clear signal that Leo wants to position the Holy See as a moral authority on the trajectory of AI.
The text is dated May 15, exactly 135 years to the day after Pope Leo XIII signed Rerum Novarum, the landmark social encyclical that confronted the upheavals of the industrial age. Leo XIV is openly framing AI as the equivalent disruption for the 21st century.
What the Encyclical Actually Says
The document, subtitled On Safeguarding the Human Person in the Time of Artificial Intelligence, lays out several headline positions. It declares that the use of AI in warfare must be subject to “the most rigorous ethical constraints” and that handing lethal decisions to autonomous systems is “not permissible.” Leo also warns that some weapons systems are already advancing “practically beyond any human reach to govern them.”
In its most striking theological move, the encyclical declares the traditional Christian “just war” doctrine “now outdated,” arguing that modern military technology has collapsed the conditions that made the framework coherent. Force, the pope writes, can now only be justified for self-defense in the strictest sense.
Beyond warfare, Magnifica Humanitas argues that AI must serve humanity rather than consolidate wealth and power, and warns of a “temptation to build a future that excludes God.” Coverage from Vatican News notes that the letter weaves the new questions into a lineage running through Centesimus Annus and Laudato Si’.
Why It Matters
The Vatican carries no regulatory power, but encyclicals shape the moral vocabulary of more than a billion Catholics and routinely echo into policy debates. By naming autonomous weapons and AI monopolies as moral red lines, Leo is offering political cover for legislators pushing tighter controls, and pressure for the AI labs that supply defense contractors. Anthropic, whose co-founder shared the stage, is itself in an ongoing legal fight with the Trump administration over restrictions on the use of its models in military applications.
The next test is whether national bishops conferences and Catholic-affiliated universities translate the encyclical into concrete advocacy, and whether frontier AI labs cite it in their own safety frameworks. Either way, the moral case against fully autonomous lethal AI just acquired its most prominent global endorser.