How Many Souls a Person Has

The 'free soul' and 'body soul' used to compare them are modern: Ernst Arbman developed the scheme in 1927; Jan Bremmer applied it to early Greece in 1983.

Tarmo Kulmar, 'On Supposed Conceptions of Soul in Old-Estonian Religion', Folklore: Electronic Journal of Folklore 4 (1997), citing Ernst Arbman, 'Untersuchungen zur primitiven Seelenvorstellung', Le Monde Oriental 20 (1927); Jan N. Bremmer, The Early Greek Concept of the Soul (Princeton, 1983)

The belief, in ancient Egyptian, Chinese and early Greek sources, that a person has several souls.

Sources5 sources

Primary source

Liji (Book of Rites), Jiao te sheng (郊特牲), Jiao te sheng, on sacrifice and the two soulsThe hun-breath returns to heaven and the bodily po returns to earth, so sacrifice seeks the dead in both yin and yang.
魂氣歸于天，形魄歸于地

Scholarship

Jan Assmann, trans. David Lorton, Death and Salvation in Ancient Egypt, 2005, chapter 'The Ba', section 'The Ba in the Sky, the Corpse in the Netherworld'The offering spell sends the ba up and the corpse down, while the ka and the mummy are the forms in which the deceased was present in the tomb and received offerings.
the ba belongs to the category of a “free soul” that could separate itself from the body
Tarmo Kulmar, On Supposed Conceptions of Soul in Old-Estonian Religion, Folklore: Electronic Journal of Folklore 4, 1997, opening section and referencesThe free-soul/body-soul scheme for comparing soul beliefs comes from Wilhelm Wundt and was developed by Ernst Arbman (1927).
Wundt's theory of the pluralism of souls in archaic religions was developed further by Ernst Arbman
Jan N. Bremmer, The Early Greek Concept of the Soul, 1983, publisher's descriptionBremmer argues the early Greeks distinguished a free soul active outside the body from a body soul, later replaced by a single soul.
before Homer the Greeks distinguished between two types of soul