When it comes to private universities, businesses, or social media, the would-be censors are our fellow-citizens, not the state. Private entities like Facebook or Twitter, not to mention Yale or Middlebury, have broad rights to regulate and exclude the speech of their members. Likewise, online mobs are made up of outraged individuals exercising their own right to speak freely. To invoke the First Amendment in such cases is not a knock-down argument, it’s a non sequitur.

John Stuart Mill argued that the chief threat to free speech in democracies was not the state, but the “social tyranny” of one’s fellow citizens. And yet today, the civil libertarians who style themselves as Mill’s inheritors have for the most part failed to refute, or even address, the arguments about free speech and equality that their opponents are making.

The two ancient concepts of free speech came to shape our modern liberal democratic notions in fascinating and forgotten ways. But more importantly, understanding that there is not one, but two concepts of freedom of speech, and that these are often in tension if not outright conflict, helps explain the frustrating shape of contemporary debates, both in the U.S. and in Europe—and why it so often feels as though we are talking past each other when it comes to the things that matter most.

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Of the two ancient concepts of free speech, isegoria is the older. The term dates back to the fifth century BCE, although historians disagree as to when the democratic practice of permitting any citizen who wanted to address the assembly actually began. Despite the common translation “freedom of speech,” the Greek literally means something more like “equal speech in public.” The verb agoreuein, from which it derives, shares a root with the word agora or marketplace—that is, a public place where people, including philosophers like Socrates, would gather together and talk.

In the democracy of Athens, this idea of addressing an informal gathering in the agora carried over into the more formal setting of the ekklesia or political assembly. The herald would ask, “Who will address the assemblymen?” and then the volunteer would ascend the bema, or speaker’s platform. In theory, isegoria meant that any Athenian citizen in good standing had the right to participate in debate and try to persuade his fellow citizens. In practice, the number of participants was fairly small, limited to the practiced rhetoricians and elder statesmen seated near the front. (Disqualifying offenses included prostitution and taking bribes.)

Although Athens was not the only democracy in the ancient world, from the beginning the Athenian principle of isegoria was seen as something special. The historian Herodotus even described the form of government at Athens not as demokratia, but as isegoria itself. According to the fourth-century orator and patriot Demosthenes, the Athenian constitution was based on speeches (politeia en logois) and its citizens had chosen isegoria as a way of life. But for its critics, this was a bug, as well as a feature. One critic, the so-called ‘Old Oligarch,’ complained that even slaves and foreigners enjoyed isegoria at Athens, hence one could not beat them as one might elsewhere.