Fits, trances, visions, speaking in tongues, clairvoyance, out-of-body experiences, possession. Believers have long viewed these and similar involuntary experiences as religious-as manifestation of God, the spirits, or the Christ within. Skeptics, on the other hand, have understood them as symptoms of physical disease, mental disorder, group dynamics, or other natural causes. In this sweeping work of religious and psychological history, Ann Taves explores the myriad ways in which believers and detractors interpreted these complex experiences in Anglo-American culture between the mid-eighteenth and early twentieth centuries.