Love it or hate it, the freedom to say obnoxious and subversive things is the quintessence of what makes America America. But our say-almost-anything approach to free speech is actually relatively recent, and you can trace it back to one guy: a Supreme Court justice named Oliver Wendell Holmes. Even weirder, you can trace it back to one seemingly ordinary 8-month period in Holmes’s life when he seems to have done a logical U-turn on what should be say-able.  Why he changed his mind during those 8 months is one of the greatest mysteries in the history of the Supreme Court.  (Spoiler: the answer involves anarchists, a house of truth, and a cry for help from a dear friend.)  Join us as we investigate why he changed his mind, how that made the country change its mind, and whether it’s now time to change our minds again. This episode was reported by Latif Nasser and was produced by Sarah Qari. Special thanks to Jenny Lawton, Soren Shade, Kelsey Padgett, Mahyad Tousi and Soroush Vosughi. Support Radiolab by becoming a member today at Radiolab.org/donate.      further reading: Thomas Healy’s book The Great Dissent: How Oliver Wendell Holmes CHanged His Mind - And Changed the History of Free Speech In America (the inspiration for this episode) plus his latest book Soul City: Race, Equality and the Lost Dream of an American Utopia. The Science article that Sinan Aral wrote in 2018, along with Soroush Vosughi and Deb Roy: “The Spread of True and False News Online” Sinan Aral’s recent book The Hype Machine: How Social Media Disrupts Our Elections, Our Economy and our Health - And How We Must Adapt Zeynep Tufekci’s newsletter “The Insight” plus her book Twitter and Teargas: The Power and Fragility of Networked Protest Nabiha Syed’s news website The Markup Trailer for “The Magnificent Yankee,” a 1950 biopic of Oliver Wendell Holmes Anthony Lewis, Freedom for the Thought that We Hate: A Biography of the First Amendment