If we could say that ancient Egypt had a psychology, we would then have to say that its fundamental notion is the ka, and the problem becomes what the ka is.
Jaynes proposes that the ka is the foundational psychological category of ancient Egypt and argues that its semantic instability across translation — spirit, ghost, double, vital force — is best resolved by reading it as a bicameral hallucination of absent or dead others.
, The Origin of Consciousness in the Breakdown of the Bicameral Mind, 1976thesis