Hailed as the "first freedom," free speech is the bedrock of democracy, and it is subject to erosion in times of upheaval. Today, in democracies and authoritarian states around the world, it is on the retreat.

In this episode, based on the book Free Speech, Michael Shermer and Jacob Mchangama discuss the riveting legal, political, and cultural history of the principle, how much we have gained from it, and how much we stand to lose without it. 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.