Leo, in his first encyclical, insists ownership of AI data must not be left solely in private hands.

Pope Leo XIV has called for the “disarming” of artificial intelligence (AI), warning that “new forms of slavery” are tied to its rise.

The Catholic Church leader warned on Monday against “a race for ever more powerful algorithms and larger datasets,” driven by “the desire to secure geopolitical or commercial dominance”.

His concerns regarding AI were presented in his first encyclical, titled “Magnifica Humanitas” (Magnificent Humanity), in person at the Vatican. Encyclicals are one of the highest forms of teaching from a pontiff to the church’s 1.4 billion members.

Leo insisted that ownership of AI data must not be left solely in private hands, called for policymakers 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,” Leo said.

The Catholic leader continued by calling for “robust ⁠legal frameworks, independent oversight, informed users and a political system that does not abdicate its responsibility”.

“AI now demands to be disarmed, freed from logics that turn it into an instrument of domination, exclusion, and death,” he said. “Like nuclear energy, it must be at the service of all and of the common good.”

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.

‘Push in better direction’

Pope Leo presented the encyclical alongside AI experts, including Christopher Olah, co-founder of US giant Anthropic.

Anthropic is embroiled in a legal battle with the United States military after opposing the use of its technology for lethal autonomous warfare and mass surveillance.

At the presentation, Olah said AI companies operate “inside a set of incentives and constraints that can sometimes conflict with doing the right thing”.

He welcomed input from outside actors like the Catholic Church to “push events in a better direction”, saying that “the questions raised by AI are bigger than the AI research community”.

Olah highlighted three areas he said required ⁠urgent attention: the risk of widespread job losses, the need to ensure that AI benefits are extended worldwide, and the unresolved question of how to interpret increasingly complex and sometimes opaque system behaviour.

‘Just war’ theory ‘outdated

In the encyclical, Leo also sounded the alarm over AI-directed weaponry, saying it was “not permissible to entrust lethal” decisions to tech.

Leo has repeatedly clashed with the White House over the US-Israel war on Iran and its use of religion to justify conflict.

The “just war” theory, espoused recently by the administration of US President Donald Trump, was “outdated”, Leo wrote, adding that “no algorithm can make war morally acceptable”.