This book endorses an ecumenical naturalism toward all cognition, which will illuminate the long-recognized and striking similarities between features of mental disorders and features of religions. The authors emphasize underlying cognitive continuities between familiar features of religiosity, of mental disorders, and of everyday thinking and action. They contend that much religious thought and behavior can be explained in terms of the cultural activation of maturationally natural cognitive systems, which address fundamental problems of human survival, encompassing such capacities as hazard precautions, agency detection, language processing, and theory of mind. The associated skills are not taught and appear independent of general intelligence. Religions’ representations cue such systems’ operations. The authors hypothesize that in doing so they sometimes elicit responses that mimic features of cognition and conduct associated with mental disorders. Both in schizophrenia and in religions some people hear alien voices. The inability of depressed participants to communicate with or sense their religions’ powerful, caring gods can exacerbate their depression. Often religions can domesticate the concerns and compulsions of people with OCD. Religions’ rituals and pronouncements about moral thought-action fusion can temporarily evoke similar obsessions and compulsions in the general population. A chapter is devoted to each of these and to the exception that proves the rule. The authors argue that if autistic spectrum disorder involves theory-of mind-deficits, then people with ASD will lack intuitive insight and find inferences with many religious representations challenging. Ecumenical naturalism’s approach to mental abnormalities and religiosity promises both explanatory and therapeutic understanding.