Christopher Ferguson is a professor of psychology at Stetson University and the author of, "How Madness Shaped History: An Eccentric Array of Maniacal Rulers, Raving Narcissists, and Psychotic Visionaries." In this episode, Meghan Murphy speaks with him about mental illness, personality disorders, and "madness," and how these have all shaped history, as well as about how our modern understanding of things like anxiety, depression, and narcissism, is impacting discourse, politics, and individual lives.