Pope Leo urged governments to slow down and closely regulate the development of AI systems in his first major document, released on Monday, warning that they spread misinformation, prioritise conflict and risk leading the world down a path of unending war.
The first US pope also expressed concern at a Vatican event launching the text that some autonomous weapons systems have advanced “practically beyond any human reach to govern them”. The event was also attended by Chris Olah, a co-founder of Anthropic, one of the world’s top AI companies.
Leo, who has adopted a more forceful tone in recent months and has drawn the ire of US President Donald Trump after criticising the Iran war, made a range of impassioned appeals to world leaders in the lengthy document, known as an encyclical.
The first US pope called for ownership of AI data not to be left solely in private hands, for policy-makers to protect the rights of workers and keep children safe from the technology, and urged the cooling of competition between AI companies.
“What is needed is a more active political involvement that is capable of slowing things down when everything is accelerating,” said Leo in the text, entitled “Magnifica Humanitas” (Magnificent Humanity).
The pope called for “robust legal frameworks, independent oversight, informed users and a political system that does not abdicate its responsibility.”
Encyclicals are one of the highest forms of teaching from a pontiff to the Church’s 1.4 billion members.
Monday’s highly anticipated text, spanning nearly 43,000 words, has been in the works nearly since Leo’s election as pope a little more than a year ago.
The document, which addressed AI as its main theme, also decried the number of wars roiling the world, lamented the weakening of multilateral organisations and warned that arms industry profits were a driving force behind conflicts.
“The past 60 years have been marked by conflicts of astonishing brutality, often affecting civilian populations on a massive scale,” stated Leo, in the English-language text.
“Humanity is slipping into a violent culture of power, where peace no longer appears as a responsibility to be taken on, but as a fragile interval between conflicts,” he said.
At the Vatican event on Monday, Anthropic co-founder Olah thanked Leo for addressing the problems raised by the disruptive, new technology. He said firms like his faced strong commercial pressures and needed outside scrutiny.
“Every frontier AI lab, including Anthropic, operates inside a set of incentives and constraints that can sometimes conflict with doing the right thing,” Olah said. Anthropic is the company that produces the Claude AI tools.
In his encyclical, Leo also made one of the clearest statements yet from a pope repudiating the just war theory, a doctrine the Church has used since at least the fifth century to evaluate global conflicts.
The doctrine, which generally says that wars should only be waged in order to defend against aggression, has also been invoked by Trump administration officials, including Vice President JD Vance, a Catholic, to defend the Iran war.
“The ‘just war’ theory which has all too often been used to justify any kind of war, is now outdated,” wrote Leo.
“The use of force, violence and weapons reflects a relational poverty that always has disastrous consequences for civilian populations.”
Leo also expressed concern that leaders could start wars to distract citizens from domestic issues.
“We cannot rule out the possibility that some leaders may consider armed conflict as an effective way of diverting attention from domestic problems and a cynical tool for managing difficulties,” he stated.
The pope said any use of AI in warfare “must be subject to the most rigorous ethical constraints” and called it “not permissible” to entrust AI systems with lethal decisions.