The Bicameral Mind, or Split Brain
When the corpus collosum is split surgically in epileptics, there becomes "two minds", with the right and left hemispheres acting and thinking separately. In normal people, the right and left hemispheres must act in an integrated, or at least semi-integrated manner, with the right hemisphere in charge of planning and organization,and the left in charge of speech and analyzing.
There are studies that show that we make some decisions before we consciously think about them. Is this the right hemisphere making these decisions, before the left(which we think of as "I" has a chance to analyze and come to a decision? Is the right hemisphere the "subconscious"? Does this subconscious have it's own sense of "I"? Does everyone really consist of two minds in one, that are so integrated, you can't tell the difference?
The Third Chakra and the Third Stage of Alchemy
I consider the seven chakras and the seven stages of alchemy to correspond. I think it is all the same thing, described in different ways. The third, or solar plexus chakra, deals with personal willpower, or choice. The third stage of alchemy deals with the separation of solar and lunar sides of the mind. I think this is the separation of the right and left hemispheres, or the two minds described above. (which is of course a psychic phenomena, and not a biological one). At this stage of alchemy, you "separate the wheat from the chaff", discarding the crap in your mind, bad behaviors, deciding what is morally good,and choosing to keep what is the good over the bad. Reintegration occurs at the fourth stage, conjunction. If you choose the crap at this stage, you do not reach conjunction, and do not evolve spiritually.