ROME (OSV News) -- Nobel laureates called Pope Leo XIV's encyclical "Magnifica Humanitas" a "clarion call" and "a giant step forward" for the prevention of AI-driven nuclear warfare as they gathered in Rome July 16 to sign a declaration urging a global treaty banning artificial intelligence from nuclear launch systems.
The signing, held under the gaze of an ancient statue of Julius Caesar in the Senatorial Palace on Rome's Capitoline Hill, capped two days of closed-door meetings at the Vatican Gardens in Castel Gandolfo, where more than two dozen Nobel laureates met with former heads of state, religious leaders, academics, and artificial intelligence researchers from organizations including Google DeepMind, Aaru and Anthropic.
Speaking in response to a question from OSV News at the press conference at the conclusion of the summit, Arthur B. McDonald, a Canadian astrophysicist and recipient of the 2015 Nobel Prize in Physics said many scientists welcomed Pope Leo's encyclical as "a document for humanity."
McDonald said the pope was uniquely positioned to warn the world about the dangers posed by artificial intelligence alongside the continuing threat of nuclear weapons.
"We are really facing ... a crisis for humanity right now," he said, calling the encyclical "a very timely thing for him to do."
Maria Ressa, the Filipino journalist who received the 2021 Nobel Peace Prize, lauded Pope Leo's leadership on the issue and courage to call out the moral challenges posed by artificial intelligence.
"Now the scientists are coming together with faith," she said. "Pope Leo's encyclical was a clarion call for leadership."
James E. Muller, an American cardiologist who co-founded the International Physicians for the Prevention of Nuclear War, which received the 1985 Nobel Peace Prize, called Pope Leo's critique of nuclear deterrence and the new arms race in the encyclical's fifth chapter "a giant step forward."
Titled the "Rome Declaration on an Unarmed and Disarming Peace in the Age of Artificial Intelligence and Nuclear Weapons," the declaration lays out six principles addressing AI governance, nuclear disarmament and the risks posed by emerging technology. It calls for an international treaty ensuring that no automated system is ever allowed to make the final decision to launch a nuclear weapon, and that "meaningful human control" is preserved over such decisions.
The declaration also urges AI developers to publish and be held accountable for the principles guiding their models' behavior, and states that no company or government should pursue fully automated, self-improving AI systems without the ability to monitor or halt them. It calls for nuclear-armed states to conduct reviews aimed at protecting their arsenals from unauthorized interference by AI, and for renewed negotiations toward the verifiable elimination of nuclear weapons under existing nonproliferation treaties.
The declaration opens by stating that humanity faces "a defining moment" as the nuclear age and the age of AI converge, arguing that humanity failed to prevent a permanent state of nuclear fear after the development of atomic weapons and warning against repeating that mistake with AI.
Echoing the words of Nobel Laureates Albert Einstein and Bertrand Russell in the 1955 manifesto highlighting the danger of nuclear weapons, the declaration says, "We appeal as human beings to human beings: remember your humanity, and forget the rest," adding "our survival and the survival of future generations are at stake."
David Gross, who won the 2004 Nobel Prize in physics, argued that public pressure, not government leaders, would ultimately drive change.
"If young people were informed of the current danger ... they would again be marching in the streets," Gross said after signing the declaration.
The three-day summit, called the Global Nobel Laureates Assembly on Artificial Intelligence and Nuclear War, drew roughly 200 delegates and was co-sponsored by institutions including the University of Chicago's Existential Risk Laboratory, the University of Notre Dame, Harvard Medical School, the Bulletin of the Atomic Scientists, International Physicians for the Prevention of Nuclear War, and The Catholic University of America.
Actress Sharon Stone attended as an honorary peace ambassador, and a member of the Russian Academy of Sciences also took part, a presence that advocates for nuclear disarmament welcomed given Russia's large nuclear arsenal.
Daniel Holz, a University of Chicago astrophysicist who studies black holes, said the Rome gathering itself embodied Pope Leo's message.
"This meeting ... is a lived example of the encyclical," he said. "We are doing the work that the encyclical specifically is talking about."
Several senior Vatican officials also addressed the conference, including Cardinals Ángel Fernández Artime, Fabio Baggio, Silvano Maria Tomasi, Mauro Gambetti and Baldassare Reina, the vicar general of the Diocese of Rome.
Father Andrea Ciucci, the president of the Pontifical Academy for Life, said, "I'm very proud of the event because (on) this occasion … the leaders of the different religions demonstrate that we can work together … in favor of humanity."
Cardinal Reina said the declaration makes clear that "no machine, no algorithm, and no autonomous system" should determine decisions affecting humanity's survival.
"Decisions concerning life and death, peace and war, and the future of peoples and generations yet to come must remain under full, responsible, and meaningful human control," he said.
