A Course in Miracles Topic - Split Mind

The mind that dreams that the separation is real, is split from changeless Reality. The divided mind needs to be healed before awakening can occur. 

Your mind is one with God's. Denying this and thinking otherwise has held your ego together, but has literally split your mind.     T-4.IV.2:7.

The calm being of God's Kingdom, which in your sane mind is perfectly conscious, is ruthlessly banished from the part of the mind the ego rules.      T-4.III.10:1.

 Any split in mind must involve a rejection of part of it, and this is the belief in separation. The Wholeness of God, which is His peace, cannot be appreciated except by a whole mind that recognizes the Wholeness of God's creation.               T-6.II.1:1,2.

The mind is therefore confused, because only One-mindedness can be without confusion. A separated or divided mind must be confused.               T-3.IV.3:3,4.

Perception always involves some misuse of mind, because it brings the mind into areas of uncertainty. The mind is very active. When it chooses to be separated it chooses to perceive. Until then it wills only to know. ... The mind chooses to divide itself when it chooses to make its own levels. But it could not entirely separate itself from spirit, because it is from spirit that it derives its whole power to make or create.   T-3.IV.5:1-4,8,9.