Dual Personality: The idea of this simplest form of multiple personality is culturally and historically almost universal

“This idea of the basic duality of human personality is culturally and historically almost universal. The ancient Chinese called these two independent consciousnesses hun and po, the ancient Egyptians the ka and the ba, and the ancient Greeks the Daemon and the Eidolon. In each case, the two entities shared their senses and perceptions of the external world but interpreted those perceptions with regard to their own history, knowledge, and personality.

“For the Greeks, the relationship was an unequal one. The higher self, the Daemon, acted as a form of guardian angel or higher self over its lower self, the Eidolon. The Stoic philosopher Epictetus wrote: God has placed at every man's side a guardian, the Daemon of each man, who is charged to watch over him; a Daemon that cannot sleep, nor be deceived. To what greater and more watchful guardian could He have entrusted each of us? So, when you have shut the doors, and made darkness in the house, remember, never to say that you are alone; for you are not alone. But God is there, and your Daemon is there. The belief was that the Daemon had foreknowledge of future circumstances and events and as such could warn its Eidolon of the dangers. It was as if in some way the Daemon had already lived the life of its Eidolon” (1).

1. Wikipedia. https://en.wikipedia.org/wiki/Ernest_Hilgard