Pope Leo XIV says artificial intelligence must be “disarmed” as world leaders and private companies increase the technology’s use in many human activities, including war.

On Monday, in the first encyclical of his papacy, titled Magnifica humanitas: On Safeguarding the Human Person in the Time of Artificial Intelligence, the pope warned against “a race for ever more powerful algorithms and larger datasets” driven by “the desire to secure geopolitical or commercial dominance”.

The leader of the Catholic Church presented the encyclical at the Vatican alongside AI experts, including Christopher Olah, the cofounder of the United States-based AI giant Anthropic.

Encyclicals are letters written by the pope and sent to Catholic bishops. In recent decades, they have become one of the highest forms of teaching from the pope to the church’s 1.4 billion members.

What did the pope say in his first encyclical, and why is it significant? Here’s what we know:

What did the pope say about AI?

Since he was elected in May 2025, Leo has made the topic of artificial intelligence a cornerstone of his papacy.

According to the Vatican News, he spoke in November about how the technology must be used in a responsible manner in the healthcare sector.  A month later, he said AI should not hinder new generations and added that it is important “to restore and strengthen” young people’s “confidence in the human ability to guide the development of new technologies, such as artificial intelligence, and not see this development as following an inevitable path”.

But in making AI the thrust of his first encyclical, the pope has turned his concerns into religious guidance to be communicated throughout the largest Christian denomination in the world, to which half the world’s Christians belong.

In his encyclical, which spans nearly 43,000 words, the pope insisted that AI must not be left solely in private hands and called on policymakers to protect the rights of workers and keep children safe from the technology. He also urged AI companies to cool down their competition.

Issuing a “special appeal” to the developers of AI, he said: “Developers bear a particular ethical and spiritual responsibility, for every design choice reflects a vision of humanity.”

“What is needed is a more active political involvement that is capable of slowing things down when everything is accelerating,” Leo said.

Olah, who spoke at the presentation of the encyclical, said AI companies operate “inside a set of incentives and constraints that can sometimes conflict with doing the right thing”. He acknowledged that AI developers need to focus on ensuring that there are no widespread job losses due to the technology and address the unresolved question about how to interpret increasingly complex and sometimes opaque system behaviour.

The pope called for “robust ⁠legal frameworks, independent oversight, informed users and a political system that does not abdicate its responsibility”.

“Artificial intelligence 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.”

The pope also warned that AI is normalising war.

In March, the US military confirmed using a “variety” of AI tools in the US-Israel war on Iran as concerns grew about mounting civilian casualties in the conflict. In 2024, Al Jazeera and other media outlets revealed that Israeli-linked AI systems, such as Lavender and Gospel, had helped generate thousands of military targets in Gaza

“For this reason, the development and use of AI in warfare must be subject to the most rigorous ethical constraints, to guarantee respect for human dignity and the sanctity of life and to avoid a race to develop such arms,” the pope wrote.

He also sounded the alarm over AI-directed weaponry, saying it was “not permissible to entrust lethal” decisions to technology.

The pope has also 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 US President Donald Trump’s administration is “outdated”, Leo wrote, adding that “no algorithm can make war morally acceptable.”

How significant are the pope’s views on AI?

In recent years, Silicon Valley has been investing extensively in AI. In January, Amazon, the second-largest private employer in the US after Walmart, laid off 16,000 employees, the latest round of sweeping layoffs due to AI. In October, The New York Times reported that the company had plans “to replace more than half a million jobs with robots”.

Besides job losses, AI data centres, which train and run AI models to carry out tasks, have also threatened to displace people from their homes in countries like India.

Moreover, according to UNICEF, “the growing prevalence of AI-powered image or video generation tools that produce child sexual abuse material marks a significant escalation in risks to children through digital technologies.”

Against this backdrop, the warning about AI marks the first time that a pope has made pushing back against Big Tech the central focus of an entire encyclical.

Past popes have addressed technology at conferences and in sections of their encyclicals.

In his 2015 encyclical, which focused on the environment and climate change, Pope Francis dedicated a section to technology and spoke about how technology should benefit the world and not deepen divisions and inequality.

In October 2021, speaking from the Vatican to the World Meeting of Popular Movements via video, Francis also said: “It is clear that technology can be a tool for good, and truly, it is a tool for good, which permits dialogues such as this one, and many other things, but it can never replace contact between us. It can never substitute for a community in which we can be rooted and which ensures that our life may become fruitful.”

“In the name of God, I ask the technology giants to stop exploiting human weakness, people’s vulnerability, for the sake of profits without caring about the spread of hate speech, grooming, fake news, conspiracy theories and political manipulation,” Francis added.

In his 2009 encyclical, Pope Benedict XVI also explored technological development in one section and warned that it should not promote dehumanisation.

What else did Leo say?

While Leo’s encyclical largely focused on AI, he also addressed the Catholic Church’s role in slavery and “sincerely asked for pardon” in the name of the Vatican.

The Vatican has insisted it always has upheld the dignity of all human beings as children of God. But a series of 15th-century directives from the Vatican authorised Portuguese sovereigns to conquer Africa and the Americas and enslave non-Christians.

Past popes have apologised for Christians’ involvement in the transatlantic slave trade. But no pope has ever publicly acknowledged or apologised for the role that past popes played in condoning colonisation and enslavement by European rulers.

“It is impossible not to feel deep sorrow when contemplating the immense suffering and humiliation endured by so many in stark contrast to their immeasurable dignity as persons infinitely loved by the Lord,” Leo wrote.

“For this, in the name of the church, I sincerely ask for pardon,” he added.

“This constitutes a wound in Christian memory, one from which we cannot consider ourselves detached,” he added.

Shannen Dee Williams, historian at the University of Dayton in the US state of Ohio and author of a 2022 history of American Black Catholic nuns called Subversive Habits, welcomed the apology as a “monumental step toward the kind of essential truth-telling and reparation that many Catholics have prayed and worked to witness”.

“The Catholic Church has never been an innocent bystander in the history of white supremacy,” Williams told The Associated Press.

“Black Catholics have waited a long time to hear the Vatican speak honestly about the church’s leading roles in the transatlantic slave trade and chattel slavery and thus by extension the enduring systems of anti-Black racism in the world today.”