The New Discourses Podcast with James Lindsay, Episode 21 In 1945, even as the Nazis fell from power, Karl Popper told us how to find the line where free, liberal societies are in imminent danger in his book The Open Society and Its Enemies, most simply summarizing a crucial part of the argument in a short footnote about "The Paradox of Tolerance." There, Popper lays out a short summary of when a free society should and must not tolerate intolerant movements if it is to survive.