Dr. Michael Stone, professor of clinical psychiatry at Columbia, dropped by Big Think's offices yesterday to talk about serial homicide, torture, mass murder, sexual slavery, and other cheery topics. Host of the Discovery Channel show "Most Evil," Stone has created a 22-point scale for evildoers, ranging from self-defense to extreme sadism (a la Ted Bundy or John Wayne Gacy). In addition to discussing his scale—replete with lurid examples—Stone walked us through the neurobiology of evil. In psychopaths, he explained, the orbitofrontal cortex and the amygdala function differently than in normal brains. Stone also gave us a glimpse of what it's like inside the minds of serial killers and stalkers.