Slatestarcodex reviews a book https://slatestarcodex.com/2020/06/01/book-review-origin-of-consciousness-in-the-breakdown-of-the-bicameral-mind/

before a theory of the mind took hold emotions were scattered in the body and inner voices were gods. This can be read in the Iliad, before it was repurposed by editors with a theory of the mind

“Children don’t have theory of mind, at least not very much of it, and more than half of them have imaginary friends. Jaynes has done some research on the imaginary friend phenomenon, and argues that a better term would be “hallucinatory friend”

“For a while in the 80s, psychiatrists were really into multiple personality and tried diagnosing everyone with it, and sure enough all those people would admit to having multiple personalities and it would be very exciting. Then the APA told the psychiatrists to stop, people stopped talking about multiple personality as much, and now the condition is rarer”

“tulpamancy, the idea of cultivating multiple personalities”

“I conclude that giving yourself multiple personalities is actually pretty easy under the right circumstances. Those circumstance are a poor theory of mind (I think borderlines are naturally bad at this) and a cultural context in which having a multiple personality is expected.

Jaynes says ancient people met both criteria”

“Every ancient culture has near-identical concepts of a god who sits inside of you and tells you what to do. The Greeks have their daemons, the Romans their genii, the Egyptians their ka and ba, and the Mesopotamians their iri. The later you go, the more metaphorically people treat these. The earlier you go, the more literal they become”