The Oneness of the whole, or the wholeness of the One, being God, is ultimately powerful and unconditional love. You cannot conquer, or divide, or diminish unconditional love. It exists omnipresent, that's true, it exists like that. Now if God, by God's own infinite wisdom and love, decides to allow a cup of Light to be used in such a way as a soul, and for the purpose of incarnating into the human condition to our level, the Light involved in that is our soul. Our soul is that Light, that one cup, that small amount, which was purely, divinely God.
All souls are equal at the soul level.
The soul doesn't evolve, the personality does. To state that the soul evolves at all is not correct. Your personality can be evolved - highly evolved, lesser evolved, or no evolvement at all to where you're just stagnant. You have the ability to create negative karma. To go backwards, to be born with certain characteristics and personality that can be culturally conditioned, or decommissioned, if you will, and go pretty much backwards.