More than 150 faculty members at the University of Chicago are pushing back on a controversial letter from the school’s dean of students that told incoming freshmen not to expect trigger warnings or intellectual safe spaces on campus.

The letter, published Tuesday in the Chicago Maroon, does not explicitly endorse the use of trigger warnings, but it criticizes efforts to prohibit them. While acknowledging that they have a range of opinions on the topic, the professors asked students to “speak up loudly and fearlessly” with requests for trigger warnings, which provide advance notice of content that could be upsetting to students.

“Those of us who have signed this letter have a variety of opinions about requests for trigger warnings and safe spaces. We may also disagree as to whether free speech is ever legitimately interrupted by concrete pressures of the political. That is as it should be,” they wrote in the letter.

“But let there be no mistake: such requests often touch on substantive, ongoing issues of bias, intolerance, and trauma that affect our intellectual exchanges. To start a conversation by declaring that such requests are not worth making is an affront to the basic principles of liberal education and participatory democracy.”

In a letter sent to incoming freshmen last month, Dean of Students Jay Ellison said the university does not support trigger warnings or the “creation of intellectual ‘safe spaces’ where individuals can retreat from ideas and perspectives at odds with their own.” The letter became part of a growing national debate over the use of trigger warnings in higher education. Proponents have advocated for their use on a class syllabus or at the beginning of a lecture, while others contend they represent a threat to academic freedom.

“The history of ‘safe spaces’ goes back to gay, civil rights, and feminist efforts of the mid–20th century to create places protected from quite real forces of violence and intimidation. They also served as incubators of new ideas away from the censure of the very authorities threatened by these movements,” faculty members wrote in the letter published on Tuesday.

“It would be naïve to think that the University of Chicago is immune from social problems. Yet the administration confusingly disconnects ‘safe spaces’ it supports (see the list of mentoring services on the College’s own website) from ‘intellectual safe spaces’ that it does not, as if issues of power and vulnerability stop at the classroom door.”

Read the full letter in the Chicago Maroon.

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Write to Katie Reilly at Katie.Reilly@time.com.