Hailed as the “first freedom,” free speech is the bedrock of democracy. But it is a challenging principle, subject to erosion in times of upheaval. Today, in democracies and authoritarian states around the world, it is on the retreat. In , Jacob Mchangama traces the riveting legal, political, and cultural history of this idea. Through captivating stories of free speech’s many defenders—from the ancient Athenian orator Demosthenes and the ninth-century freethinker al-Rāzī, to the anti-lynching crusader Ida B. Wells and modern-day digital activists—Mchangama reveals how the free exchange of ideas underlies all intellectual achievement and has enabled the advancement of both freedom and equality worldwide. Yet the desire to restrict speech, too, is a constant, and he explores how even its champions can be led down this path when the rise of new and contrarian voices challenge power and privilege of all stripes. Meticulously researched and deeply humane, demonstrates how much we have gained from this principle—and how much we stand to lose without it.