86:4.3

Early man was also much concerned about his breath, especially in cold climates, where it appeared as a cloud when exhaled. The breath of life was regarded as the one phenomenon which differentiated the living and the dead. He knew the breath could leave the body, and his dreams of doing all sorts of queer things while asleep convinced him that there was something immaterial about a human being. The most primitive idea of the human soul, the ghost, was derived from the breath-dream idea-system.