The Growing Dominance of the Ego

What sets the mental-rational structure apart from the previous three structures is that it is the most separated from “Origin.” In it, human consciousness, which had previously felt a fundamental connection to the world around it, was now unattached and “free.” The subject/object divide became firm. Consciousness and the world were clearly experienced as different, radically opposed realities. In the mental-rational structure, for the first time man learned how to think about the world as something separate from himself, and this also meant the growing dominance of the ego, the verbal “I” which, we’ve seen, inhabits the left brain.

Gary Lachman
The Secret Teachers of the Western World