Pope Leo warns AI revolution driven by ‘idolatry of profit’

Pope Leo has called for robust regulation of AI and limits on its use for warfare, as he warned of the dangers of a technological revolution driven by “the idolatry of profit”.

In his first encyclical letter since his elevation to the papacy last year, Leo slammed the use of AI in conflicts. The technology has been used during US President Donald Trump’s campaign in Iran to help make decisions on bombing targets.

“It is not permissible to entrust lethal or otherwise irreversible decisions to artificial systems,” the US-born Pope told the world’s 1.4bn Catholics, calling for an “identifiable and verifiable” chain of responsibility and “effective, self-aware and responsible human control” over bomb targets.  

“When a decision to strike becomes automated or opaque, the risk of abdicating responsibility increases,” he wrote in the encyclical Magnifica Humanitas, considered an authoritative moral teaching on contemporary challenges.

“All systems used in a war setting must guarantee the possibility of retracing and reconstructing decision-making processes, so that accountability and blame are not collapsed into ‘the machine’.” 

The encyclical comes after the Pope publicly criticised the US’s campaign in Iran, angering Trump and triggering fierce debate with Washington over the conflict. US vice-president JD Vance and defence secretary Pete Hegseth have tried to argue the attack on Iran was consistent with Christianity, citing the Catholic Church’s “just war” theory. But the Vatican rejected the claim, which the pontiff rebuffed again in the encyclical.

“Without prejudice to the right to self-defence in the strictest sense, it is important to affirm that the ‘just war’ theory, which has all too often been used to justify any kind of war, is now outdated,” Pope Leo wrote.

He also warns that “opaque algorithms”, controlled by powerful private companies, threaten “new forms of dehumanisation” and calls for conscious efforts by governments and society to mitigate AI’s potential negative impacts in many areas, including education, the labour market and personal relationships.

“Technology in and of itself is not a solution to humanity’s problems just as it is not inherently evil,” he wrote. “In practice, however, technology is never neutral, because it takes on the characteristics of those who devise, finance, regulate and use it.” 

Criticising the transhumanist and posthumanist vision of powerful Silicon Valley entrepreneurs such as Peter Thiel and Elon Musk, the Pope wrote that AI was developing in an intellectual milieu in which some people are deemed “less useful, less desirable and less worthy”.

He demands “transparency and accountability” for all AI tools used in public life to protect people from having their potential limited by machines.

“When data and algorithms influence credit distribution, personnel selection or access to services and opportunities, it is necessary that decisions be understandable, contestable and subject to oversight, so that individuals are not reduced to mere profiles,” the Pope wrote. 

He also warned of AI’s ability to feign empathy and understanding, “creating the illusion of a relationship with a real person”, leading to risks that people “may gradually lose the very desire to form genuine human connections”.

The Holy See has been engaging with AI ethicists and technologists from top Silicon Valley tech companies for more than a decade, trying to wrestle with a technology it sees as potentially unleashing both the best and the worst of humanity.