An early reference to the Chinese theory of the "soul" records an explanation on human life offered by a learned statesman in 535 BCE: the earthly aspect of the soul (po) first comes into existence as the human life begins; after po has been produced, the heavenly aspect of the soul (hun) emerges. As generally understood, hun is the spirit of a person's vital force that is expressed in consciousness and intelligence, and po is the spirit of a person's physical nature that is expressed in bodily strength and movements. Both hun and po require the nourishment of the essences of the vital forces of the cosmos to stay healthy. When a person dies a natural death, his or her hun gradually disperses in heaven, and the po, perhaps in a similar manner, returns to earth. A violent death may cause the hun and po to linger...