For Walter Isaacson, Elon Musk was the next logical subject. The biographer-of-geniuses wrote the definitive book on Steve Jobs, the Apple cofounder who “brought us into the personal digital revolution.” The next big revolution, according to Isaacson, “was life sciences, the ability to edit our genes”—which led him to the trailblazing biochemist Jennifer Doudna. A few years ago, though, he was looking around, wondering what the next innovation would be. “To me, there were a couple of ’em: sustainable energy, AI—making our robots safe—and space travel. Musk was a trifecta for that.” (This was before Musk, the cofounder of Tesla and SpaceX, would buy Twitter, fire most of its employees, rename the platform X, and more or less kill what was left.)

On Monday evening, Isaacson was speaking to Richard Stengel, who served in the Obama administration as under secretary of state for public diplomacy and public affairs, at the Perelman Performing Arts Center, the swanky new cultural institution at the World Trade Center site. There, Stengel and Isaacson, who have been friends for more than two decades, discussed some of the storied biographer’s past subjects and Isaacson’s whirlwind two years embedded with Musk.

Musk, one of the world’s most divisive (and richest) people, is obviously alive; his story has continued to play out beyond the final chapter of Isaacson’s book. Lately, that story has included amplifying antisemitic conspiracy theories and telling advertisers who boycotted X over such incendiary content to “go fuck” themselves. “He really is a genius when it comes to material properties, when it comes to engineering,” said Isaacson. But he is “not a genius” on “human emotions.” Isaacson attributed this in part to the billionaire’s “brutal upbringing,” as well as the fact that Musk is “on the autism spectrum.” Musk first publicly disclosed his Asperger’s syndrome diagnosis while appearing on Saturday Night Live in 2021.

Isaacson, the former editor of Time, chair of CNN, and CEO of the Aspen Institute, stayed away from discussing Musk’s recent controversies during Monday night’s event. But in sharing insights gleaned while reporting the biography, he offered some explanations for the behavior. Take Ukraine, for instance; one of the biggest revelations to come out of Isaacson’s book was that Musk, according to a passage in the biography, “secretly ordered his engineers to turn off his company’s Starlink satellite communications network near the Crimean coast last year to disrupt a Ukrainian sneak attack on the Russian naval fleet.” The passage was in an excerpt published a few days before Elon Musk came out in September, prompting an outcry and leading Musk to explain that the “Starlink regions in question were not activated. SpaceX did not deactivate anything.” Isaacson then went on to “clarify” the matter on X, also telling New York magazine that he had “misinterpreted” Musk. “I thought he had just made that decision. In fact, he was simply adhering to a policy he had previously implemented,” Isaacson wrote to the publication. While Stengel and Isaacson didn’t get into all of this on Monday, Isaacson did say: “He loves playing superhero on the world stage. I mean, he’s Captain Underpants.” Last month, amid the Israel-Hamas war and accusations that antisemitic content was flourishing on his social platform, Musk visited Israel and met with top leaders, including Israeli prime minister Benjamin Netanyahu.

Near the end of the discussion, Stengel asked Isaacson about the pros and cons of writing the biography of a living person versus a dead one. “Doing somebody who’s living is a lot more exhausting,” said Isaacson. “After I did [Henry] Kissinger, it was such a roller coaster ride that I said, Okay, I’m going to do somebody who’s been dead for 200 years, and then did [Benjamin] Franklin.” Then he did Jobs—writing the book at the Apple cofounder’s request and releasing it less than three weeks after Jobs’s death. “After Steve Jobs, I was like, Okay, dead for 500 years,” said Isaacson, whose next biography was of Leonardo da Vinci. The most significant difference, said Isaacson, is the ability to observe and talk to a living person versus just reading documents left by the dead. “I knew maybe a thousand times more about the curve of the iPhone than I did about the flying of the kite,” he said.

Stengel’s last question for Isaacson was which of his subjects—living or dead—he’d most like to have dinner with. The “most fun” companion would be Franklin, Isaacson said, also describing him as “the person you need right now the most.” He added, however, that “the most interesting to talk to” would be da Vinci. “I thought you would say Einstein,” Stengel said. “I’d be kind of intimidated,” replied Isaacson, smiling sheepishly.