FORTUNE — It’s been Sheryl Sandberg’s year. The Facebook (FB) COO took the working world by storm this past year with the publication of her book, Lean In. The part-memoir, part-advice tome for young professional women flew off shelves, selling one million copies and topping the New York Times Bestsellers list. Sandberg pushes for women to not shy away from the pursuit of professional success. Her argument is compelling but seems at odds with another popular dictum on the topic published last summer.
Anne-Marie Slaughter’s “Why Women Still Can’t Have It All” adds a different, though far from dissenting, voice to Sandberg’s “Lean In” movement. The former State Department director, who worked under Hillary Clinton, left her government job and returned to her teaching job at Princeton in hopes of spending more time with her teenage sons. Slaughter’s piece explains that decision and addresses the institutional and social mores that forced her to slow her career. Four days after Slaughter’s article was published by The Atlantic, the article gained one million views.
Having two intelligent women express different, well-reasoned opinions on the same topic was far too boring on its own, so the media declared it a catfight.
On Thursday morning at Fortune’s Most Powerful Women Summit in Washington, D.C., Slaughter sat onstage with Fortune’s Leigh Gallagher to clear the air. (Sandberg spoke the day before.) “At 43, I could have written Lean In,” Slaughter explained. At that time in her life, she said, she had not encountered a challenge she couldn’t power through or solve with money. By 53, she said, things changed.
Slaughter, who is now the president and CEO of the New America Foundation, never expected her article to appeal to such a large crowd. She described the piece’s target: smart, ambitious women who were forced to take a step back from the leadership track due to personal or financial reasons. “Life happened to them, and they weren’t superhuman. Or they didn’t have enough money, or they got shut out when they tried to have a more flexible workplace,” she solemnly said. And the “Lean In” conversation, which puts accountability on the individual, makes these women “feel like failures.”
“I see much less of an ambition gap and much more of a workplace and society that isn’t allowing us to use the talent that is multiplied well beyond this room,” said Slaughter. She invoked Bill Gates, who once said that there are two fundamental forces in human nature: competition and care for others. In society, Slaughter continued, we value competition and devalue care. Gallagher questioned her point, asking how she intends to alter institutional systems and policy to change such values. Slaughter used her mother’s dinner party behavior as an example. In the 1960s, her mother used to put little vases of cigarettes out on the table. “If you did that in New York today, you’d be arrested. That’s a huge value change,” Slaughter said. “Why can’t we have a sea change about the value of caring about each other and the value of competition?”
Gerri Elliot, an executive vice president at Juniper (JNPR) who previously worked at IBM (IBM) and Microsoft (MSFT), took a moment to thank Slaughter, saying she had to step back from the prime of her career due to a family issue. She then cited her interest in both Sandberg and Slaughter’s arguments. “The only difference I see between the two of you is Sheryl has young’uns and you have teenagers and honey, they are completely different.”
Slaughter laughed, then added that she and Sandberg are not on opposite sides. She said she’s a feminist to the core, and she reasoned that she “went through a life experience that made me realize that there are millions of women out there who need a bigger tent. They need more than, ‘Honey, you can do it if you try hard enough.’”
Only good can come from Slaughter’s attempt to broaden the “having it all” conversation. “I want to have a debate [with Sandberg] where we can be both honest and encouraging at the same time.” The invitation’s open for Sandberg, who will hopefully soon realize that leaning in doesn’t necessarily mean you have to do so alone.