Robert J. Zimmer, a mathematician who as president of the University of Chicago championed diversity in the recruitment of students and by protecting free expression on campus, died on May 23 at his home in Chicago. He was 75.

Mr. Zimmer, who presided over the university from 2006 to 2021, was instrumental in shepherding what became known as the Chicago Principles, a set of guidelines recommended by the Committee on Free Expression. “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,” the faculty committee concluded.

Mr. Zimmer balked at the notion that unfettered free speech would jeopardize the cause of inclusion. “Inclusion into what?” Mr. Zimmer had wondered in a speech delivered in 2017. “An inferior and less challenging education? One that fails to prepare students for the challenge of different ideas and the evaluation of their own assumptions? A world in which their feelings take precedence over other matters that need to be confronted?”

For Mr. Zimmer, “that kind of education wouldn’t count,” The New York Times said.