In July, Chandler Davis, an American Canadian mathematician and human rights defender, delivered welcoming remarks at a panel for the “Azat Miftakhov Days Against the War” in Ukraine from his hospital bed in Toronto, a vase of sunflowers by his side.

The event was in support of the mathematician Azat Miftakhov, a 29-year-old graduate student from Moscow State University who has been detained in Russia since February 2019. It was co-organized by a committee of mathematicians, of which Davis was a founding member, who have lobbied for Miftakhov’s release. Davis noted that the panel was also there to advocate for others in prison for their beliefs, particularly Russians speaking out against war and “more generally in support of freedom of conscience and peace.”

“It means a lot to me to be opening this session, because I have a special bond to Azat Miftakhov,” he said. “Years ago, I was a political prisoner, too, not in Russia but in the USA. I was almost as young as Azat is now. Like Azat, I had a wife standing by me outside.”

Davis, who died on September 24 at 96, was a polymathic mathematician and a professor emeritus at the University of Toronto, where he taught for 30 years. He was also a poet, composer, science-fiction writer, and lifelong fighter for political, academic, and intellectual freedom. He once advised: “In mathematics and in life, it is not OK to give up on a problem or a cause just because the struggle is difficult.”

Michael Harris, a mathematician at Columbia University, and a fellow founding member of the Miftakhov committee, met Davis in the late 1980s and soon knew that he could count on him for backing and “thoughtful criticism if I were to speak out on controversial questions,” Harris said. “Without that support I may never have dared to express myself in public as a mathematician.”

Davis was always looking for ways to make silenced voices heard. He opposed the war in Vietnam and defended Palestinian rights against Israeli apartheid. He was part of what he described as a “band of rebels” within the mathematical community that helped establish the Association for Women in Mathematics and the National Association of Mathematicians for underrepresented minorities, and he was an original member of Science for the People, a movement of radical scientists. According to a 2018 book documenting its history, the organization “mobilized American scientists, engineers, teachers, and students who yearned to practice a socially and economically just science, rather than one that served militarism and corporate profits.”

I met Davis about 20 years ago when he was a source—and an enthusiast brimming with knowledge and advice—for my first book, a biography of the classical geometer Donald Coxeter. Coxeter helped Davis get a job at the University of Toronto, after he was blacklisted from US academia and imprisoned for refusing to testify before the House Un-American Activities Committee (HUAC).

In 1960, Davis served a six-month sentence at a federal correctional institution in Danbury, Conn., where he passed the time working on a prison farm, refining his Russian, and doing mathematics. His 1963 paper on convex curves contained a footnote with something of an acknowledgment: “Research supported in part by the Federal Prison System. Opinions expressed in this paper are the author’s and are not necessarily those of the Bureau of Prisons.”

After his release, he wrote a December 1960 article for The Nation, “So You’re Going to Prison!” in which he said that he’d missed jingling coins, wearing a necktie, drinking a glass of wine and smoking a reefer, and his sex life. While he called being incarcerated “pretty dreary,” he ended the piece by celebrating political prisoners: “You may have accomplished something just by going, if your offense was well chosen.”

Born in Ithaca, N.Y., on August 12, 1926, Davis came from a family of activists and revolutionaries. He described his formative years as “growing up subversive.” His father, a journalist and professor of economics, had preceded him as a target of HUAC and had obtained conscientious objector status during World War I—but the younger Davis, 17, enlisted in the US Navy during World War II. (He came to regret his service after the use of nuclear weapons).

In the 1940s and ’50s, he published science-fiction stories on subjects as varied as nuclear war, corporate culture, communication, cooperation, robots, eugenics, gender, labor, language, and first contact. He also published a fanzine, Blitherings, a compendium of musings on politics and culture, philosophy, and mathematics. A 2010 anthology of his work, It Walks in Beauty, is the first male-authored book from the feminist Aqueduct Press.

In 1950, Davis obtained his doctorate in mathematics from Harvard—where, over the course of six weeks in 1948, he met and married his wife, Natalie Zemon Davis, now an acclaimed historian to whom President Barack Obama awarded the 2012 National Humanities Medal.

In 1952, prior to her husband’s HUAC entanglements, Zemon Davis had written “Operation Mind,” co-authored with the psychologist Elizabeth M. Douvan. It reviewed previous HUAC interrogations and urged protests against the planned hearings in Michigan. The pamphlet was anonymous, but the FBI found the print shop and discovered that one Chandler Davis had signed the invoice and paid the bill—ultimately leading to his subpoena and imprisonment.

In 1953, the House Un-American Activities Committee subpoenaed Davis. It was “a deflating moment,” he wrote in an autobiographical account titled “The Purge.” Investigators had dug up just six items: “half wrong, and mostly vague: manifestly, just guesswork.” He felt that more of his efforts should have been worthy of the FBI’s scrutiny. Davis had been an active leftist since high school—and for several years he was a member of the Communist Party. (He became disillusioned with communism in the early 1950s and had left the party before his HUAC encounter.)

When Davis, then a professor of mathematics at the University of Michigan, came before the Committee in 1954, he refused to answer questions about his political actions or opinions on First Amendment grounds. And he refused to invoke his Fifth Amendment right against self-incrimination, which led—as planned—to his indictment for contempt of Congress. He’d invited the indictment in order to challenge the constitutionality of McCarthyism. “The point was to get the Supreme Court to accept the argument in my defense that the hearing was illegal and so nothing I did at it (cogent or not) could be the basis for a finding of guilt,” he explained.

The University of Michigan fired him, and in 1959, the Supreme Court refused (by a vote of six to two) to hear his case.

Although he couldn’t find another permanent job in the United States, he held temporary appointments at the Institute for Advanced Study in Princeton, and the Courant Institute at New York University. In 1962, at the behest of Coxeter, he emigrated to Canada and became a professor at the University of Toronto.

Mathematically, Davis was known for creating the theory of the dragon curve (jointly with Donald Knuth)—a fractal curve that can be created by folding a strip of paper in half repeatedly. When the paper is unfolded, the resulting mountain and valley creases produce a pattern of 90-degree right and left turns that generates the curve. (Several iterations of the dragon curve were featured in Michael Crichton’s novel Jurassic Park.) Most of Davis’s work was in linear algebra and operator theory in Hilbert space, numerical analysis, geometry, and algebraic logic. A number of mathematical results carry his name, including the Davis-Kahan-Weinberger dilation theorem (with William Kahan and Hans Weinberger).

A fellow of the American Mathematical Society, Davis was well known for his dedication to The Mathematical Intelligencer. In 1987, he joined the editorial team to manage a column. Four years later, he became editor in chief, and he served as co–editor in chief from 2005 to 2013, with Marjorie Senechal, a mathematician and professor emerita at Smith College. Senechal called Davis “an editor’s editor.” She said, “no typo, no non sequitur, no infelicity, no stupidity” escaped his eagle eyes.

In 2014, upon Davis’s retirement from the journal, a special issue was devoted to his life’s work. He contributed a poem, “Successors,” which read, in part: “More messages come in than we can read; / I cherish more than I can understand, / but I have fathomed some. Pass it on.”

Depending upon one’s perspective, Davis might have been talking about mathematics in that poem or life’s wider pageant.

It reminded me of a recent interview in which he declared himself “a radical contingentist”—that is, he believed that “the contingent rules,” a notion he’d explored in a lecture on “The Next Thousand Years or So.” There is no bound on knowing the laws of history, he said, but our knowledge will inevitably fall short, and small changes could have arbitrarily large consequences (per the French mathematician Henri Poincaré). “I can be a contingentist and still care very much what purpose I pursue, and what purpose you pursue and whether our attempts to foresee outcomes are sound,” he wrote. “Confident predictions are out the window,” he added, “but I do not throw responsibility out with them.”