The author argues that there exist terrestrial rational beings, distinct from pure spirits, who possess both body and soul, are born and die, and can receive salvation or damnation. He marshals theological and philosophical argument, medico-psychological observation, and anecdotal case histories to support claims of material intercourse with humans. Drawing connections to folklore figures such as fauns, sylphs, and goblins, the work examines moral, pastoral, and doctrinal consequences and offers an original, systematic demonstration of these entities within a Christian framework.