The use of psychedelic drugs plants is rising, and with it the number of reports narrating encounters with otherworldly visionary beings. Approaches to these experiences have often been literal, archetypal or dismissive. Evolutionary psychology and the cognitive science of religion suggest innate and non-imagistic mental foundations for these phenomena arising from easily-triggered evolutionary functions during emotive periods of high cognitive demand. Such functions include agent detection, social intelligence faculties and metacognition. This wide-ranging book explores how our deepest mental processes predispose us as humans to believe in supernatural agents, and presents a new hypothesis of how these same cognitions facilitate the emergence of those agents to become present when psychedelic drugs and plants are ingested. Bruce concludes that visionary beings shimmer within as awe-inspiring products of the mind, an experience which rests at the heart of what it is to be human.