Human beings are quick to give offense, and to take it. Some people find discord stimulating, but most of us believe that disagreement with our fellows is disagreeable. The food we eat, clothes we wear, and books we read can bother those who don’t share our ways. These seemingly minor matters pale next to political and religious differences over what is advisable, just, or righteous.

Civility, the quality of character meant to smooth relations roiled by these disagreements, mitigates insistence on one’s own way and hair-trigger sensitivity to others’ different practices and beliefs. Civil people, reluctant to give or take offense, pull their punches and hold their tongues. The “true gentleman,” John Henry Newman wrote in 1852, “carefully avoids whatever may cause a jar or a jolt in the minds of those with whom he is cast.”

Aristotle’s Nicomachean Ethics omits civility, since he examined moral virtue’s relation to human perfection rather than to domestic tranquility. Modern thinkers such as Thomas Hobbes and John Locke recognize civility as a virtue that is, in Hobbes’s words, a “means of peaceable, sociable, and comfortable living.” Civility, then, promises that the manner of our disagreements can defuse the fact of those disagreements. We may cohere as a people by agreeing to disagree, and on how to disagree.

A shared commitment to civility can easily be abused, however. Jim Leach, chairman of the National Endowment for the Humanities under President Obama, told Americans that “those who seek unity by respecting diversity” exemplify civility, in contrast to those who “press debilitating cultural wars or extreme ideological agendas.” The “civil” may seek to silence their opponents by dismissing the substance of their position as a violation of civility’s protocols. Thus misconstrued, civility restrains speakers from giving offense but incites thin-skinned listeners to take it.

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This emphasis on policing discourse, Teresa Bejan shows in her impressive first book, Mere Civility: Disagreement and the Limits of Toleration, is traceable to the deficient theory and practice of civility in the political philosophy of Hobbes and Locke. Bejan, a political scientist at the University of Oxford, believes Hobbes was worried that the utterances and glances we now call “microaggressions” would lead to a war of all against all. To prevent this cataclysmic reversion to the state of nature, his Leviathan was to govern beliefs on matters both fundamental and minor. “Difference without disagreement” is the Hobbesian vision of civility according to Bejan, since “peace required uniformity.” The only latitude Leviathan affords its subjects is to maintain a “civil silence” about their real beliefs, lest argument lead to insult, and insult to violence.

Locke’s teaching on religious toleration promised “difference and disagreement” (emphasis added), while aspiring to keep disagreement civil. A less contentious, intolerant, and dogmatic people would tolerate those with whom they disagree. Locke saw the need to transform “the beliefs, attitudes, and dispositions of individuals” by reforming Christian doctrine and elevating the virtue of civility. For Locke, people must manifest “a Carriage” such that others recognize “Charity, Love, or Good-will” in their disposition. This outward carriage is most likely when it reflects a sincere, inward persuasion of mutual respect. Disagreement on religious matters is consistent with civil peace so long as citizens share a cultural commitment to charity, civility, and trustworthiness. Lockean uniformity seems more procedural than substantive, yet he still sees it as the glue of civil society.

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The Hobbesian and Lockean solutions reflect the central commitments among today’s liberals. Those following John Rawls’s “duty of civility” must practice a Hobbesian civil silence about “comprehensive doctrines” that undergird their theories of justice or rights. Only the less disagreeable language of “overlapping consensus” is acceptable in public debates with fellow citizens.

Bejan criticizes Locke for providing the foundation for 21st-century civility, which extends only to those who “subscribe to the relevant moral principles already.” Moreover, “time and again” Locke’s followers “set the deliberative bar quite high, placing constraints not only on the manner in which fundamental disagreements are conducted, but also on what kinds of disagreements can take place, where, and with whom.” Contemporary liberals manifest a “moralizing emphasis on sincerity” and dismiss “anyone unwilling or unable to submit to its rigors.” Anything less than full consonance between one’s inner and outer life becomes a kind of thought crime.

As a result, civility now means conforming to contemporary liberalism’s requirements, ever more elaborate and stringent. Victims of incivility, demanding “safe spaces” from opinions that offend them, manifest a passive-aggressive imperiousness when insisting that they’re entitled to others’ empathy. Faced with disagreement, the offended parties react with incivility, up to and including the violence committed earlier this year at Middlebury College and the University of California, Berkeley.

Against these intolerant conceptions, Bejan praises Roger Williams, who founded the Rhode Island colony in 1636, for offering and practicing “mere civility.” Rhode Island welcomed all: Protestants, Catholics, Jews, non-believers, and Native Americans. Unlike the Massachusetts Puritans from whom Williams fled, Rhode Island’s wall of separation between church and state was so high that the state neither administered oaths nor recognized church marriages. At the same time, Christians could proselytize heathens and heretics in the civil space “mere civility” provided. Williams himself, with singularly annoying zeal, called unbelievers and sinners to repent.

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Mere civility, as Bejan understands it, accepts real diversity of opinion but also anticipates a high degree of reciprocated disdain. After all, the Latin root of our word “tolerate” means to suffer or endure, not to welcome or encourage. She argues that Williams’s mere civility, aimed at “more conversation and more speech,” was bound to produce alienating disagreements. Governments would refrain from policing hate speech or promising safe spaces. Citizens, in turn, would manifest a “thick-skinned determination to tolerate” what they see “as others’ incivility” by acquiring a “set of habits of speaking and listening that make passionate debate possible, by allowing us to disagree, and to tolerate the inevitable contempt and disagreeableness involved in doing so.” Though we may hold our political opponents in low regard, we should listen to them and attempt to dissuade them from their erroneous views.

Bejan, then, seeks to relieve those beleaguered by an increasingly intolerant culture. She wants campus cry-bullies and diversity bureaucrats in organizations public and private to treat civility as a two-way street.

That mere civility is simple does not make it easy, however. Because the powerful can take the gloves off with impunity and zeal, the disrespected must learn to be thick-skinned. Since nothing but manners tames the powerful, mere civility can descend into worsening incivility and monolithic opinions when they brook no disagreement. The disrespected need deep convictions, akin to Williams’s Christian faith, and the enforcement of neutral law to keep the conversation going when those in power threaten and insult.

Recent campus events, however, argue that the worst are full of passionate intensity while the somewhat less bad lack all conviction. As a result, the will to violate civility is stronger than the will to preserve or restore it. Middlebury College, for example, has meted out its punishment to the student ringleaders who broke the college’s rules twice: first by preventing Charles Murray from speaking onstage, and then by making it impossible for him to speak to his audience from a remote campus location via electronic hookup. A letter will be placed in the file of each student who committed this double violation, remaining there until graduation, and then be expunged as if the violations never occurred. Campus activists have, of course, denounced this savage reprisal.

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Bejan acknowledges that Rhode Island was hardly a paradigm of successful republicanism. “Rogue’s Island,” as it came to be known, gained a “reputation for enthusiastic dysfunction that would last well into the nineteenth century.” It lacked the cohesion and public-spiritedness to protect itself from enemies domestic and foreign. The Native Americans to whom Williams extended toleration burned his beloved Providence to the ground in 1676, when Williams was 72. This is a problem for Bejan’s thesis because good examples are more important than good arguments to establish that mere civility is the most desirable standard we can realistically pursue. If 17th-century Rhode Island is the best example of mere civility in action, other arguments on its behalf, however cogent, don’t really matter.

“What Are the Chances that the American Union Will Last?” Alexis de Tocqueville asked. His answer: “What maintains a great number of citizens under the same government is much less the reasoned will to live united than the instinctive and in a way involuntary accord resulting from similarity of sentiments and resemblance of opinions.” One of Tocqueville’s greatest fears was that national unity was fading as Americans in the 1830s manifested divergent mores and destinies, traceable to the existence of slavery. Not mere civility but some robust, shared understanding was necessary, he thought, for harmonious civil coexistence even in America.

Abraham Lincoln’s Republican Party came into existence for the purpose of opposing “popular sovereignty”—Stephen Douglas’s device to settle the slavery question by not settling it. According to Douglas’s policy, Americans would agree to disagree about the issue, permitting or forbidding slavery in states and territories as residents’ opinions dictated. It became clear, however, that there are some disagreements that cannot be set aside, and some differences that cannot be split.

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Today’s disunity differs from the divisions in the 19th century. Modern liberals seem to prosecute our cultural civil war in the name of “live and let live.” Blacks should be able to become president, women to become Marines, two (for the time being, just two) people of the same sex to become spouses, women to become men, and men to become women. Liberals withhold, with extreme prejudice—uncivilly even—the spirit of live and let live from those who oppose, object to, or decline to enthuse about the string of liberal victories. The only thing intolerable is intolerance, which liberals define as an aversion to social justice, not an aversion to pluralism.

How disparate must American sentiments, opinions, and mores become before repairing national community proves impossible? How can we know whether the demise of an old consensus means a new one is being born, or that our country is simply coming apart? Could the 5th-century A.D. Romans have answered those questions? Mere civility may be a reasonable tactic for gaining space and buying time with the hopes that Americans can establish a new consensus that honors practices necessary to perpetuate a self-governing people. Mere civility is not enough to salvage a political community, however.

Perhaps, Bejan speculates, the “commonality needed to sustain a tolerant society could be much more minimal and superficial” than we think. The historical and anthropological evidence to the contrary is imposing, however. Political communities must share more than an aptitude for agreeing to disagree. Distinct communities, including national communities, are bound together by the belief that fellow citizens are members of the same team, not just adherents of the same rulebook. Absent a reckoning with this fact, Teresa Bejan’s diagnosis of civility’s decline is more persuasive than her prescription for restoring it.