Activist, critic, and novelist Todd Gitlin, widely regarded as one of America’s leading public intellectuals, has died at 79, the New York Times reports.

Gitlin, a Manhattan native, was educated at Harvard University, the University of Michigan, and the University of California, Berkeley. From a young age, he was an influential activist against nuclear weapons and the Vietnam War, becoming president of the New Left group Students for a Democratic Society in 1964.

His nonfiction books included The Whole World Is Watching: Mass Media in the Making and Unmaking of the Left, The Twilight of Common Dreams, and Letters to a Young Activist. He was also the author of three novels, The Murder of Albert Einstein, Sacrifice, and Undying.

His most recent book, Occupy Nation, was published in 2012.

Gitlin was remembered on social media by readers and colleagues. Historian Julian Zelizer wrote, “So sad to hear about Todd Gitlin's passing. He lived a remarkable life and had a major impact shaping the social justice movements of the 1960s. Gitlin will not be forgotten. His legacy will endure. May his memory be [a] blessing.”

And Gal Beckerman of the New York Times Book Review tweeted, “Todd Gitlin has left us. It’s hard to fathom the world without his capacious mind and giant heart. He was an extraordinary mentor to me and a dear friend. I will miss him.”

Michael Schaub is a Texas-based journalist and regular contributor to NPR.