University of Chicago President Robert J. Zimmer, left, is accompanied by Mayor Rahm Emanuel during a news conference in August 2016 in Chicago. Zimmer died from an aggressive form of brain cancer last Tuesday. Tae-Gyun Kim/Associated Press

Robert Zimmer, who as president of the University of Chicago reshaped debates over ideological openness on campuses by reaffirming a free-speech code that was adopted by dozens of other institutions even as they struggled to balance discourse and dissent, died May 23 at his home in Chicago. He was 75.

His wife, Shadi Bartsch-Zimmer, said he had glioblastoma multiforme, an aggressive form of brain cancer. Dr. Zimmer stepped down as university president in 2021 after 15 years in the post.

The statement unveiled under Dr. Zimmer’s leadership, known as the Chicago Principles, sought to give a contemporary upgrade to University of Chicago guidelines set down during waves of campus protests in the late 1960s against the Vietnam War. The new text restated the need to keep the university open to all speakers and political and cultural points of view.

“Concerns about civility and mutual respect can never be used as a justification for closing off discussion of ideas, however offensive or disagreeable those ideas may be to some members of our community,” wrote a faculty committee in 2014 created by Dr. Zimmer to help draft the document.

Dr. Zimmer was soon thrust into the crossfire of a polarized nation. He was hailed for taking a clear stand against ideological intolerance, including a perceived shrinking space for conservative viewpoints on many campuses. More than 80 institutions of higher education, including American University and Georgetown University, later endorsed the Chicago Principles, also known as the Chicago Statement, or used it as a framework for their own policies.

Yet Dr. Zimmer faced backlash from some scholars and student groups over the broad-brush approach of the Chicago Principles, which offers no clear guidance on what constitutes hate speech and appears hostile to campus “safe spaces” used by groups such as transgender or minority students.

Letters sent to incoming first-year students at the University of Chicago have included a synopsis of the codes set under Dr. Zimmer: “We do not support so-called trigger warnings, we do not cancel invited speakers because their topics might prove controversial, and we do not condone the creation of intellectual safe spaces where individuals can retreat from ideas and perspectives at odds with their own.”

Dr. Zimmer, a former professor of mathematics, also expanded financial assistance programs for undergraduate students and was a consummate fundraiser, bringing in six donations of at least $100 million.

Michelle Deutchman, executive director of the University of California’s National Center for Free Speech and Civic Engagement, described the Chicago Principles as an “aspirational reaffirmation of the First Amendment” that covers two ends of the spectrum: the rights of free expression and the rights for lawful protest.

“What it doesn’t address is the messy middle,” she said in an interview. “Equality, inclusivity, campus climate, the things that really are at the center of university life . . . It’s an aspiration document and that’s good, but it’s just a piece of the puzzle.”

Dr. Zimmer acknowledged the limitations. Asked in 2020 if he thought the Chicago Principles accomplished its mission, he replied: “Yes and no.” He noted that the document was intended as a reminder and not a groundbreaker. “It was not really a departure,” he added. “It’s a statement of things everybody knew was in the air for 100 years.”

His ideals were put to the test in early 2018 by a professor’s invitation to Stephen K. Bannon, an adviser to former president Donald Trump, to speak at the University of Chicago.

Student-led protests swelled after a business school professor said he wanted to host Bannon in a debate over nationalism. The university issued a statement backing the professor, saying it was “deeply committed to upholding the values of academic freedom, the free expression of ideas.” Then more than 1,000 alumni signed a petition opposing Bannon’s presence on campus. The Bannon event was eventually called off.

Other members of Trump’s inner circle had spoken at university events despite student-led protests: campaign manager Corey Lewandowski in 2017 and press secretary Sean Spicer two weeks before Trump’s 2017 inauguration. (Spicer, who would give inflated numbers for the inauguration turnout, told the University of Chicago audience he would “never go out and lie” for Trump.)

To Dr. Zimmer, intellectual tolerance was a “learned skill.”

“Most people really are very comfortable with their own free expression and not with everybody else’s. That’s just the way it is,” he told The Post in 2016. “And helping students who come in – they’re 18 years old – it requires work to help people learn how to be in this type of environment and have a productive experience out of it. And I think that’s part of a university’s responsibility, to help people do that.”

BOYHOOD OF ‘TOLERANCE’

Robert Jeffrey Zimmer was born on Nov. 5, 1947, in Manhattan and was raised in the Greenwich Village section, where his father was a doctor and his mother managed the medical office. The diversity of the West Village during his boyhood was formative for Dr. Zimmer. “You felt that tolerance in a deep way,” he recalled.

Dr. Zimmer graduated in 1958 from Brandeis University with a bachelor’s degree in mathematics. He earned a master’s degree from Harvard University in 1971 and remained for a doctorate in 1975, specializing in geometry and ergodic theory, the study of long-term patterns using statistical analysis.

After two years as an instructor at the U.S. Naval Academy, Dr. Zimmer took a teaching position at the University of Chicago in 1977 and became a full professor in the math department in 1980. (He left from 1981 to 1983 to teach at University of California at Berkeley.)

He returned to the University of Chicago, taking roles that included research positions at the Argonne National Laboratory in Lemont, Illionois, which is overseen by the university. He was a math professor and provost at Brown University from 2002 to 2006, when he was named president of the University of Chicago.

Under his direction, the university expanded its global presence with satellite sites in Beijing, New Delhi and Hong Kong. The university’s health-care complex, UChicago Medicine, added a trauma center after appeals from the surrounding neighborhood. The university also dropped admission testing requirements, including the SAT and ACT.

At the end of the 2021 academic year, Dr. Zimmer stepped down as president to become chancellor. He retired in July 2022.

His marriage to Terese Schwartzman ended in divorce. In addition to his wife, a professor of classical studies at the University of Chicago, survivors include his 104-year-old mother; three sons from his first marriage; a brother, and two grandchildren.

The Chicago Principles were left intentionally aspirational, Dr. Zimmer said. Rulemaking and free expression can turn out to be enemies, he added.

“The minute you start saying that we’re going to systematically decide what can be said and what cannot be said, and you set up the committee for making such decisions, you’ve now got the ‘speech police committee,'” he told The Post. “Which is not what you want.”