"The authors, colleagues and professors, one of psychiatry and the other of radiology and psychiatry, at the University of Pennsylvania Medical School, harvest twenty-five years of research in the neuro-physiology of religious experience to offer this engaging study of the biological realities that underlie and shape religious experience. How does the mind experience the sacred ? Why does the mind create myth ? What makes something spiritual ? Why are religious experiences so powerful ? Is myth-making, even engagement in ritual, a necessary -- perhaps even predictable -- moment in the evolution of human knowing, or of human being ?"