Psychiatry, once famously opposed to religion, has done an about-face. Like the legendary explorers of a century ago, some psychiatrists have set off into what they see as the last frontier: the spiritual self. In this moving and impeccably researched narrative, Russell Shorto tells remarkable stories of people suffering from what once were deemed spiritual afflictions, then came to be seen as purely medical disorders, and now are being treated as both.

In the process, Shorto brings to bear issues from the cutting edge of consciousness studies. He explores the shared territory of psychosis and mysticism; the changing meaning of "self," "soul," "mind," and "brain"; the theory that psychotropic drugs have a spiritual dimension; the meaning of religious terrorism; and the possibility that addiction and depression are spiritual conditions.

In weaving his case studies into a single story, Shorto delivers a concise update on the science of the mind and the newest efforts to probe the deepest meaning of human existence.