The historian Yü Ying-shih describes hun and po as "two pivotal concepts that have been, and remain today, the key to understanding Chinese views of the human soul and the afterlife".
魂 and its variant 䰟 combine the "ghost radical" 鬼, a pictogram originally showing a figure with an odd face and tail that is used independently as a word for Chinese ghosts and demons, with the character 云, a pictogram originally showing a cloud and believed to have been pronounced /*[ɢ]ʷə[r]/ or /*ɢun/ in Ancient Chinese.
魄 combines the same radical with the character 白 of uncertain origin (possibly a pictogram of an acorn to represent its inner color) but believed to have been pronounced /*bˤrak/ or /*braːɡ/ in Ancient Chinese.
The spiritual hun 魂 and po 魄 "dual souls" are first recorded in Warring States period (475–221 BCE) seal script characters.
Hun expresses the idea of continuous propagation ([zhuan] 傳), unresting flight; it is the qi of the Lesser Yang, working in man in an external direction, and it governs the nature (or the instincts, [xing] 性).
He cites the Zuozhuan (534 BCE, see below) using the lunar jishengpo 既生魄 to mean "With the first development of a fetus grows the vegetative soul".
[4] Etymologically, lunar and spiritual po < pʰak < *phrâk 魄 are cognate with bai < bɐk < *brâk 白 "white".
"[11] Yü says this ancient association between the po soul and the "growing light of the new moon is of tremendous importance to our understanding of certain myths related to the seventh day of the months.
Joseph Needham and Lu Gwei-djen, eminent historians of science and technology in China,[26] define hun and po in modern terms.
"Peering as far as one can into these ancient psycho-physiological ideas, one gains the impression that the distinction was something like that between what we would call motor and sensory activity on the one hand, and also voluntary as against vegetative processes on the other."
Farzeen Baldrian-Hussein cautions about hun and po translations: "Although the term "souls" is often used to refer to them, they are better seen as two types of vital entities, the source of life in every individual.
Both describe Tian 天 "heaven; god" duo 奪 "seizing; taking away" a person's po, which resulted in a loss of mental faculties.
In 534 BCE, the ghost of Boyou 伯有 (above) was seeking revenge on his murderers, and terrifying the people of Zheng (Duke Zhao, Year &).
[30] The philosopher and statesman Zi Chan, realizing that Boyou's loss of hereditary office had caused his spirit to be deprived of sacrifices, reinstated his son to the family position, and the ghost disappeared.
When a friend asked Zi Chan to explain ghosts, he gave what Yu calls "the locus classicus on the subject of the human soul in the Chinese tradition".
When an ordinary man or woman dies a violent death, the [魂魄] soul and spirit are still able to keep hanging about men in the shape of an evil apparition; how much more might this be expected in the case of [Boyou].
The Liji (11), compounds hun and po with qi "breath; life force" and xing "form; shape; body" in hunqi 魂氣 and xingpo 形魄.
Hun 魂 is associated with shen 神 "spirit; god" and po 魄 with gui 鬼 "ghost; demon; devil".
Han medical texts reveal that hun and po departing from the body does not necessarily cause death but rather distress and sickness.
[45][46] Han burial customs provided nourishment and comfort for the po with the placement of grave goods, including food, commodities, and even money within the tomb of the deceased.
Generations of sinologists have repeatedly asserted that Han-era people commonly believed the heavenly hun and earthly po souls separated at death, but recent scholarship and archeology suggest that hunpo dualism was more an academic theory than a popular faith.
"[52] Another Han text, the Fengsu Tongyi says, "The vital energy of the hun of a dead person floats away; therefore a mask is made in order to retain it."
There the people have tattooed faces and blackened teeth, they sacrifice flesh of men, and pound their bones to paste ... O soul, come back!
Go not down to the Land of Darkness, where the Earth God lies, nine-coiled, with dreadful horns on his forehead, and a great humped back and bloody thumbs, pursuing men, swift-footed ...[56] Hun 魂 and po 魄 spiritual concepts were important in several Daoist traditions.
For instance, "Since the volatile hun is fond of wandering and leaving the body during sleep, techniques were devised to restrain it, one of which entailed a method of staying constantly awake.
Both fangshi and daoshi 道士 "Daoist priests" developed methods and rituals to summon hun and po back into a person's body.
(4)[59]For visualizing the ten souls, the Baopuzi "Truth on Earth" chapter recommends taking dayao 大藥 "great medicines" and practicing a fenxing "divide/multiply the body" multilocation technique.
In Shangqing Neidan "Internal Alchemy", Baldrian-Hussein says, the po plays a particularly somber role as it represents the passions that dominate the hun.
One resides in the ancestral tablet erected to his memory, if the head of a family; another lurks in the coffin or the grave, and the third departs to the infernal regions to undergo its merited punishment.
[66] Seven po may stand for the qiqiao 七竅 "seven apertures (in the head, eyes, ears, nostrils, and mouth)" or the qiqing 七情 "seven emotions (joy, anger, sorrow, fear, worry, grief, fright)" in traditional Chinese medicine.