Auditory hallucination is one of the most awe-inspiring, terrifying, and ill- understood tricks of which the human psyche is capable. In the age of modern medical science, we have relegated this experience to nothing more than a biological glitch. Yet as Daniel B. Smith puts forth in Muses, Madmen, and Prophets, some of the greatest thinkers, leaders, and prophets in history heard, listened to, and had dialogues with voices inside their heads. In a fascinating quest for understanding, Smith examines the history of this powerful phenomenon, and delivers a ringing defense of the validity of unusual human experiences.