Free Speech on Campus. By Sigal Ben-Porath. University of Pennsylvania Press. 128 pages; $19.96 and £15.99.

INCITEMENT to violence is one of few exceptions the Supreme Court has carved out from America’s most celebrated constitutional right: the right to free speech. But on today’s college campuses, struggles over speech extend well beyond expression that encourages physical harm. In 2015 a lecturer at Yale was excoriated—and felt compelled to resign—after she raised questions about the college’s plea that students avoid culturally insensitive Halloween costumes. The next year the dean of students at the University of Chicago caused a stir by coming out against “intellectual ‘safe spaces’” where students “retreat from ideas and perspectives at odds with their own”. Students have repeatedly succeeded in having invitations to controversial speakers cancelled, and even made tenured faculty fear provocative comments.

These students think they are sticking up for the vulnerable, practising a kind of self-defence. Others wonder what happened to the spirit of inquiry that is meant to be the point of a university. Nearly half of students advocate some curbs on expression, and nearly a fifth think it acceptable to shut down unacceptable speech with violence. On October 9th, the president of Texas Southern University got in on the act, cancelling a speech by a Republican legislator in mid-stream after student protesters tried to disrupt it. The talk hadn’t been scheduled through proper “university procedures”, he said.

These developments are alarming, but it is a mistake, argues Sigal Ben-Porath of the University of Pennsylvania, to conclude that today’s student activists have no serious concerns. In “Free Speech on Campus”, a reflection on her time as chairman of her university’s committee on open expression, Ms Ben-Porath urges a re-thinking of the battles over campus speech. Her book begins with a broad defence of free inquiry: “Speech, including controversial speech, is central to teaching and learning” and to campus life. She rejects speech codes, mandatory sensitivity training and systems whereby students report episodes of professor bias to administrators. She criticises the president of Williams College for stepping in last year to cancel a talk by a lecturer with racist views who had been invited by a student group. It is wrong, Ms Ben-Porath argues, “to forgo free speech for the sake of administrative order”.

Still, she says, the activists have a point. As colleges become more diverse, the students they teach often find campus life stifling or unwelcoming. Any university effort to protect freedom of speech, Ms Ben-Porath suggests, is incomplete without genuine attempts to include all students in the speaking. She calls this combination of robust speech protection and harnessing all voices “inclusive freedom”.

Though she disdains speaker disinvitations and other limits on speech, Ms Ben-Porath has no trouble with trigger warnings to alert students to a potentially troubling reading. These are “good pedagogy”, not a “surrender to weakness and laziness of thought”. She also speaks up for much-maligned safe spaces where students can find comfort in the company of others who share an aspect of their identity. But the university itself should not be one big intellectual safe space; protecting students’ dignity is not the same as protecting them from challenges to their ideas.

That is a sound analytical distinction, but it is not clear how it should work out in practice. Consider the mêlée in March at Middlebury College, where Charles Murray, best known for his 1994 book arguing that IQ variation between racial groups is a cause of inequality, was invited to speak about his book from 2012 on divisions between American whites. Hundreds of alumni signed a letter calling Mr Murray’s invitation “unacceptable and unethical”, and the students were never going to listen to him. After jeers made holding the public lecture impossible, he gave his talk in an improvised video studio. Afterwards, chaos erupted and Mr Murray’s host, a Middlebury professor, suffered a concussion.

Violently disrupting a speech is antithetical to intellectual openness. But the protesters felt that Mr Murray’s presence itself was an assault—in Ms Ben-Porath’s words, a “dignitary harm” on minority students. Administrators often plead for civility at times like these, but Ms Ben-Porath argues that civility can mean privileging peace and quiet over vigorous challenges.

How can colleges manage a sea of strident voices while neither suppressing inquiry nor sanctioning hecklers like those who shut down a “white supremacist” humanities class at Reed College? (The class in question featured, for the objecting students, too many white men on the reading list.) Ms Ben-Porath thinks that volunteer monitors at public events, to step in when anyone’s right to speak is disrupted, might help, and that students should be encouraged to seek out and talk to people with whom they disagree. Administrators should aim for a more democratic campus culture. She admits, though, that there are no “quick fixes”. That is putting it mildly. Her suggestions are rather gauzy in the face of a new wing of America’s left that no longer esteems freedom of speech as a value worth fighting for.