Dear Teo,
I just started the book, and as I see it, there are no real levels or boundaries. That is just an illusion. What we think obstructs us from unity consciousness does not really exist.
Ken Wilber states that if we look for the 'self' we will not find it. The feeling of being an isolated self, on whatever level, is an obstacle to unity consciousness.
Words of the great Buddhist Padmasambhava:
"If the seeker himself, when sought, cannot be found, thereupon is attained the goal of seeking, and also the end of the search itself."
I am only into chapter four, but I cannot see how there can be actual, real levels if there
is no real 'self?'