On February 28, just a few weeks before the United States plunged into lockdown, the world lost the visionary physicist and mathematician Freeman Dyson. Although widely celebrated for his expansive scientific achievements, eulogizers have given scant attention to his progressive political imagination and longtime identification as a pacifist and socialist.

Five years ago, when the New York Times asked him which writers he’d invite to a literary dinner party, Dyson chose three women he already knew so he “would not need to waste time on formal introductions”: the classical archeologist Joan Breton Connelly, the science fiction writer Mary Doria Russell, and me. He said he selected his guests because all of our books explored “the mystery of self-sacrifice,” of what inspired ordinary men and women to ignore their own self-interest for the sake of the greater good. The key to the future, he seemed to indicate, hinged on understanding the roots of altruism.

For Dyson, the mysteries of human behavior were just as deep and enduring as the mysteries of the universe. In the sheer breadth of his interests, Dyson embodied the ideal of the Renaissance man, widely knowledgeable across multiple fields of inquiry. In addition to his groundbreaking work in astrophysics and quantum mechanics, Dyson reveled in the humanities and social sciences, exploring big questions not everyone has the courage to ask.

He had some wild ideas about life beyond our planet. He theorized about extraterrestrials powering their civilizations by building spheres around their suns as well as genetically engineered trees that could grow on comets. But Dyson had social dreams, too, dreams about how to make our world more peaceful, cooperative, and kind. A profound admirer of Mohandas Gandhi, he cared as much about poetry and politics as he did about planets. Over more than six decades at the Institute for Advanced Study in Princeton, his incisive mind inspired generations of scholars across many disciplines, including me.

I first met Dyson when standing behind him in the lunch line as he pondered his midday meal choices. Starstruck and bashful, I introduced myself and mumbled something about working in Bulgaria.

“Bulgaria?” His eyes lit up. He had a schoolmate who had died in Bulgaria fighting with the anti-fascist partisans and had many questions. “You must come and see me,” he said.

And so began our thirteen-year friendship forged through lunch dates, email exchanges, and one real-life literary dinner party. Over hours of shared conversation, we discussed the ramifications of artificial wombs and women’s rights, the appeals of European populism, the psychological impacts of new technologies, and his pleasure in having both grandchildren and “grandbooks” (books written by his children).

But mostly, we argued about socialism and capitalism.

Born in 1923, Dyson was “brought up as a socialist” in England. In response to an undergraduate student who asked him in 2012 about the nonscience issues he had struggled with during his life, Dyson replied, “adapting my socialist principles to a capitalist society” after he moved from Great Britain to the United States.

Dyson was sympathetic to the ideals of people like his Winchester classmate Frank Thompson, a member of the Communist Party of Great Britain, who fought with the Bulgarian partisans and was murdered in 1944, and of Elena Lagadinova, the youngest female partisan who went on to become a prominent socialist champion for women’s rights at the United Nations. But later in life, Dyson’s eldest daughter convinced him that capitalism could “be creative,” and he defended the possibility of a third way.

“Capitalism is a risky game,” he wrote to me in an email on November 17, 2018, articulating a social-democratic vision for his ideal society. “With big gaps between winners and losers. Socialism tries to minimize risk, and succeeds in making a society kinder to losers. I am saying that we should aim to create a society combining the advantages of socialism and capitalism. Big freedom and big prizes for winners. Safe jobs and help with child-raising for losers.”

While I tended to be much more critical of capitalism, he believed that human innovation could solve the world’s problems if the right people put their minds to it. Although famously a contrarian — including, unfortunately, on the issue of climate change —  Dyson was definitely one of the right minds asking the right kinds of questions.

When I interviewed him in 2007 for the magazine Geek Monthly, he still spoke of his own “socialist principles” and how the “idea of extravagant wealth is evil in itself.” Like his esteemed colleague at the Institute for Advanced Study, Albert Einstein, Dyson was an open-minded scientist who understood the rational arguments for a more humane economic system. The global bank of genius is much depleted without him.

But what I miss most about him was his tireless hope for the future. In late 2017, I sent Dyson a fear-infused missive about the rise of right-wing leaders and neofascist violence in Eastern Europe. The world was going to hell in a handcart, I wrote him. Dyson, ever the nonagenarian wise man, soothed my fears by trying to put everything in perspective.

“Frank and Elena and I have the advantage of having grown up in the 1930s,” he wrote. “If you grew up in the 1930s it is glaringly obvious that the world is better now than it was then, and you cannot help being an optimist. The troubles of today are real, but nothing like as pervasive and threatening as the troubles of the 1930s. We should give humanity credit for some amazing achievements in the last eighty years.”

He listed the transformation of Germany and Japan from dictatorships into democracies, the end of colonial rule in Africa and Asia, the technical improvements in agriculture that resulted in more stable food supplies, and the eradication of abject poverty in places like India and China.

“The disasters and failures that loom so large in your view of the world today are quite small when you compare them with the injustices and miseries of the past,” Dyson wrote.

He believed that human creativity and tenacity would save us as it had in the past. And it wouldn’t require extraterrestrial vegetation or star-encompassing megastructures, but simply a collective willingness of ordinary men and women to self-sacrifice and keep fighting for a better world.

At the end of 2020, all that sometimes feels like science fiction to me. But as the coronavirus continues to ravage the planet and Trump raves like mad King George in the White House, I find myself desperately striving to capture some of Dyson’s optimism.