Brandeis’s test was based on his Jeffersonian faith in the power of what he called “free and fearless reasoning” to expose falsehood through public discussion. “If there be time to expose through discussion the falsehood and fallacies, to avert the evil by the processes of education,” Brandeis wrote, “the remedy to be applied is more speech, not enforced silence. Only an emergency can justify repression.” As a result, the United States Supreme Court now protects free speech more vigorously than any other judiciary in the world.

Brandeis’s faith in reason—and his four justifications for protecting all speech not intended to and likely to cause violence—is being questioned in our social-media age. Twitter, Facebook, and other platforms have accelerated public discourse to warp speed, creating virtual versions of the mob. These companies are based on a business model that’s now being called “enrage to engage.” Inflammatory posts based on passion travel further and faster than arguments based on reason. Because of this, some critics are suggesting that America’s free-speech tradition should be reconsidered or amended.

These arguments are unpersuasive, and Musk is correct to reject them. In fact, all four of Brandeis’s arguments weigh heavily against any central authority, whether government or Twitter, exercising the power to monitor free speech.