There is today a crisis in psychiatry. Even the former director of the National Institute of Mental Health, Thomas Insel, has said: “Whatever we’ve been doing for five decades, it ain’t working.” The field requires a completely fresh look, and clinical psychologist Bruce Levine—a man often at odds with his profession—enlists the early Enlightenment philosopher Baruch de Spinoza to help work through the problem. Readers unfamiliar with Spinoza will be intrigued by the modern relevance of hi...