Two and a half millennia ago, Aristotle made one of the most fundamental statements ever about human society: "Man is by nature a political animal."

Aristotle meant more than that people group together for their survival and reproduction. People actually group together to strive for higher goods beyond mere preservation. This is politics—a community’s pursuit of a good life together.

And it is our speech that makes us political, Aristotle teaches. Through speech we communicate our needs, but we also argue about the deeper things—what is right and wrong, "the just and the unjust," as Aristotle puts it. Politics is about governing society justly, and it is our speech, our rational discourse, that makes politics possible.

A brief new book by Greg Lukianoff, Freedom from Speech, sheds valuable light on what Aristotle sees as the foundation of our political nature. Lukianoff examines the state of free speech in our culture. He examines not the First Amendment, although as the head of the free-speech organization Foundation for Individual Rights in Education, or FIRE, he is certainly qualified to do so. Rather, Lukianoff examines "Free speech as a cultural value."

And free speech is in decline. Freedom from Speech concisely lays out the ways that speech is being limited in America. Lukianoff begins by listing a number of high profile cases where figures had their reputations tarnished and even their livelihoods threatened because of things they said, sometimes in private. He then goes on to discuss a couple of noteworthy trends in academia where speech is being curtailed.

His book focuses on academia because universities are one of the most obvious places where speech is being limited. Both "trigger warnings" and commencement-speaker "dis-invitations" have made headlines in recent months. Lukianoff excoriates both of these trends with precision. They are attempts to limit what students hear, and thus what people say. By discussing the academy at some length, Lukianoff builds on his previous book from 2012, Unlearning Liberty, which examined the decline of free speech in universities.

But Lukianoff also notes that the university cannot be the sole source of curbs on free speech. "I continue to believe that the increased national focus on punishing offensive speech stems, in large part, from the ‘bleeding out’ of the bad intellectual habits of American higher education," Lukianoff writes. "However, I do not think—nor have I ever thought—that blame for the erosion of support for the cultural value of freedom of speech can be laid entirely on the ivory tower." The erosion of free speech in other Western countries, such as Britain, or countries with democratic values, such as India, demonstrates that the problem is deeper and more pervasive than the silly movements in universities.

Lukianoff sees a deeper and more disturbing problem in Western society. The modern age has led to the creation of tremendous wealth, and with it, tremendous comfort. But such comfort gives rise to complacency: "A society in which people can avoid physical pain comparatively easily will produce people who are less prepared to deal with it."

The same principle applies to mental comfort. "The same instinct is driving our rising desire for intellectual comfort, by which I mean a yearning to live in a relatively harmonious environment that does not present thorny intellectual challenges, and in which disagreement is downplayed or avoided altogether," Lukianoff says.

And the result of this overwhelming drive for comfort is devastating for speech: "Eventually, they stop demanding freedom of speech and start demanding freedom from speech."

Through much of his book, Lukianoff strives not to blame either the right or the left in contemporary politics for the decline in free speech. Freedom of speech is a deep issue that goes beyond any one party in a society like ours founded on the primacy of liberty. But he notes that the political left does have a basic tendency to assault speech.

Liberals, in general, are motivated fundamentally by empathy. While conservatives take their moral norms from a variety of places, such as traditional values and religion, "progressive morality is largely one-dimensional, driven primarily by the care ethic," Lukianoff says. And because liberals just want people be happy and comfortable, he argues, they attack speech they deem offensive or threatening to others.

Lukianoff’s description of liberal morality provides a useful paradigm for understanding assaults on freedom of speech, especially in liberal epicenters like most universities. It does not always hold up—progressives champion graphic and explicit art, for example, that make people uncomfortable—but the morality of empathy helps explain a lot.

But this explanation, while sympathetic and surely often correct, misses a much darker aspect of the left’s social agenda.

The left feels empathy for people, but that empathy is not guided by any sense of what is right and good for people. Like Bill Clinton, the empathic left merely "feels their pain" and wants to end it. But this myopic focus on perceived harm validates all harm, labeling harms as threats to individual lives. Every pain inhibits an individual from living the life he wants to live, and so the left’s efforts to stop all pain ultimately means that it ends up supporting all choices, regardless of whether a choice is right or good for the individual or society at large. This "ethic of validation," which often looks like the ethic of care, is the progressive vision for society.

Welfare work requirements are a good example of this ethic of validation. Before 1996, welfare recipients had to meet few, if any, requirements in order to receive aid from the government. Welfare simply alleviated physical suffering without regard to the actions the individual was taking—such as whether the individual was working. This approach to welfare is unmoored empathy at work in social policy.

Conservatives argued that work was fundamentally good for people, and as a result in 1996 the Republican Congress pushed through work requirements for welfare, tying government aid to either work or the pursuit of work. If able-bodied individuals did not pursue work, they did not receive help—even if they were suffering. The government still provided help, but the help did not simply support individuals’ choices of how they would live their lives. Welfare work requirements are shaped by a broader vision of what is fundamentally good for human life.

The progressive attempt to validate all lifestyle choices belies at best agnosticism, and at worst nihilism, toward the existence of an essential good for human life. In more Aristotelian terms, progressives deny that there is any end to human life—a goal or reason for living that should guide choices that individuals make.

Limits on speech result from this agnosticism, because speech can be very painful when it contradicts choices and exposes their insufficiency. But limiting speech makes politics much more difficult, if not impossible. If we cannot speak to each other about what is most important in life for fear of offending others and failing to validate their choices, we lose the ability to be political. We become detached individuals rather than a political community.

Freedom from Speech shows how speech is being curtailed and hollowed out in our society. By losing the freedom to reason with each other over difficult issues, we are becoming, in fact, less than human.