Freedom of speech is a fundamental principle of a free society—and of the United States in particular. It’s also deeply embedded in the founding of the Cato Institute.

When it was founded in 1977, Cato was named for Cato’s Letters, a series of newspaper essays written in the 1720s. Why that name? Because John Trenchard and Thomas Gordon, who wrote under the pen name Cato after the defender of the Roman republic who refused to submit to Julius Caesar, took the ideas of great thinkers such as John Locke and Algernon Sidney and applied them to the controversies of the day. And that has always been the approach of the Cato Institute: to apply the great principles of liberty to policy and current affairs.

In any epoch, freedom of thought and expression is one of our essential liberties. Earlier this year, Cato held a virtual Young Leaders Seminar for college students, focusing on the importance of freedom of speech as a pillar of a free society and the unique threats facing free speech in the 21st century. The seminar paid special tribute to the legacy of former Cato senior fellow Nat Hentoff, one of the great First Amendment defenders of the past half-century.

In opening that seminar, I drew on our connection to Trenchard and Gordon. I noted that the great American political historian Clinton Rossiter described Cato’s Letters as “the most popular, quotable, esteemed source of political ideas in the colonial period.” Bernard Bailyn, perhaps the most important historian of early America, wrote, “To the colonists the most important of these publicists and intellectual middlemen were those spokesmen for extreme libertarianism, John Trenchard and Thomas Gordon.”

Another historian of the American Founding, Forrest McDonald, points out that “free speech” was never a central political claim prior to the 1720s: “It was John Trenchard and Thomas Gordon … who first gave unreserved endorsement to free speech as being indispensable … and who were willing to extend the privilege to all, including those who disagreed with them.”

As Trenchard and Gordon wrote in Letter 15, “Without freedom of thought, there can be no such thing as wisdom; and no such thing as publick liberty, without freedom of speech.… This sacred privilege is so essential to free government, that the security of property; and the freedom of speech, always go together; and in those wretched countries where a man cannot call his tongue his own, he can scarce call any thing else his own. Whoever would overthrow the liberty of the nation, must begin by subduing the freedom of speech.”

So, the importance of freedom of speech was in our bones even before the Cato Institute was founded. And obviously freedom of expression is essential for the work we do and, as Trenchard and Gordon wrote, for the public liberty.

We exercise our rights of free speech in books, studies, journals, and newspapers, on the radio, television, and internet, and in seminars and public speeches. We defend the right of free speech through our advocacy, as well as in the courts, on college campuses, and in our advice to legislators and policymakers.

People often complain that free speech is being violated when a newspaper refuses to run an article, a social media company bans a controversial account, a publisher cancels a book, an NFL team won’t hire a politically outspoken quarterback, or an owner shuts down a magazine after its criticisms of an elected official. We want to encourage a culture of free speech, but all these private actors are making decisions about which ideas and controversies they want to be associated with. That’s very different from government restrictions on expression. The First Amendment forbids any “law … abridging the freedom of speech, or of the press,” not editorial decisions by private companies.

Our defense of free speech must be aimed at those on both sides of the political spectrum who seek to have local, state, or federal governments ban—or compel—the expression of certain ideas. Government remains the true threat to be guarded against, and state censorship is crucially different from the decisions of private actors, however open the latter are to fair criticism. Conflating the two opens the door to the very thing free speech guards against: control of the marketplace of ideas by the government rather than free individuals and private, voluntary society.