In 2014, Zimmer formed the Committee on Freedom of Expression whose report came to be known as the Chicago principles — a set of guidelines intended to demonstrate The University of Chicago's commitment to freedom of speech. The Chicago Principles were adopted by more than 65 colleges and universities. As Zimmer noted in an address to the Chicago Humanities Festival in 2017, the work of faculty and students to confront new and different ideas through education and research "only happens at the highest level in an environment of rigor, questioning, and free and open discourse." Zimmer also spoke on the importance of these ideas in the keynote address at the University of Vienna's Academic Freedom in the Digital Age conference.