Elon Musk celebrated his 44th birthday in July 2015 at a three-day party thrown by his wife at a California wine country resort dotted with cabins. It was family and friends only, with children racing around the upscale property in Napa Valley. This was years before Twitter became X and Tesla had a profitable year. Mr. Musk and his wife, Talulah Riley an actress who played a beautiful but dangerous robot on HBO’s science fiction series “Westworld” were a year from throwing in the towel on their second marriage. Larry Page, a party guest, was still the chief executive of Google. And artificial intelligence had pierced the public consciousness only a few years before, when it was used to identify cats on YouTube, with 16 percent accuracy. A.I. was the big topic of conversation when Musk and Page sat down to have a heated debated about whether we were doomed. The machines will destroy humanity. This argument between the two men seems prescient. The question of whether artificial intelligence will elevate the world or destroy it has framed an ongoing debate among founders, users, academics, legislators, and regulators. The controversy has pitted some of the world’s richest men against one another: Musk, Page, Zuckerberg, Thiel, Nadella of Microsoft and Altman of OpenAI. All have fought for a piece of the business and the power to shape it. At the heart of this competition is a brain-stretching paradox. The people who say they are most worried about A.I. are among the most determined to create it and enjoy its riches. They have justified their ambition with their strong belief that they alone can keep A.I. from endangering Earth. “There is disagreement, mistrust, egos,” Mr. Altman said. “The closer people are to being pointed in the same direction, the more contentious the disagreements are. You see this in sects and religious orders. There are bitter fights between the closest people.”kehr years later, there was a little-publicized but ferocious competition in Silicon Valley for control of the technology that is now quickly reshaping the world, from how children are taught to how wars are fought. The New York Times spoke with more than 80 executives, scientists, and entrepreneurs, including two people who attended Mr. Musk’s birthday party in 2015, to tell that story of ambition, fear, and money. The Birth of DeepMind Five years before the Napa Valley party and two before the cat breakthrough on YouTube, Demis Hassabis, a 34-year-old neuroscientist, walked into a cocktail party at Peter Thiel’s San Francisco townhouse and realized he’d hit pay dirt. There in Mr. Thiel’s living room, overlooking the city’s Palace of Fine Arts and a swan pond, was a chess board. Dr. Hassabis had once been the second-best player in the world in the under-14 category. “I was preparing for that meeting for a year,” Dr. Hassabis said. “I thought that would be my unique hook in: I knew that he loved chess.” In 2010, Dr. Hassabis and two colleagues, who all lived in Britain, were looking for money to start building “artificial general intelligence,” or A.G.I., a machine that could do anything the brain could do. At the time, few people were interested in A.I. After a half-century of research, the artificial intelligence field had failed to deliver anything remotely close to the human brain. Still, some scientists and thinkers had become fixated on the downsides of A.I. Many, like the three young men from Britain, had a connection to Eliezer Yudkowsky, an internet philosopher, and self-taught A.I. researcher. Mr. Yudkowsky was a leader in a community of people who called themselves Rationalists or, in later years, effective altruists. They believed that A.I. could find a cure for cancer or solve climate change, but they worried that A.I. bots might do things their creators had not intended. Mr. Thiel had become enormously wealthy through an early investment in Facebook and through his work with Mr. Musk in the early days of PayPal. He had developed a fascination with the singularity, a trope of science fiction that describes the moment when intelligent technology can no longer be controlled by humanity. With funding from Mr. Thiel, Mr. Yudkowsky had expanded his A.I. lab and created an annual conference on the singularity. Years before, one of Dr. Hassabis’s two colleagues had met Mr. Yudkowsky, and he snagged them speaking spots at the conference, ensuring they’d be invited to Mr. Thiel’s party. Mr. Yudkowsky introduced Dr. Hassabis to Mr. Thiel. Dr. Hassabis assumed that lots of people at the party would be trying to squeeze their host for money. His strategy was to arrange another meeting. There was a deep tension between the bishop and the knight, he told Mr. Thiel. The two pieces carried the same value, but the best players understood that their strengths were vastly different. It worked. Charmed, Mr. Thiel invited the group back the next day, where they gathered in the kitchen. Their host had just finished his morning workout and was still sweating in a shiny tracksuit. A butler handed him a Diet Coke. The three made their pitch, and soon Mr. Thiel and his venture capital firm agreed to put 1.4 million British pounds (roughly $2.25 million) into their start-up. He was their first major investor. They named their company DeepMind, a nod to…