Quote from A Course in Miracles Text Chapter 7 - THE GIFTS OF THE KINGDOM.

T-7.VI.8. I have repeatedly emphasized that the ego does believe it can attack God, and tries to persuade you that you have done this. 2 If the mind cannot attack, the ego proceeds perfectly logically to the belief that you must be a body. 3 By not seeing you as you are, it can see itself as it wants to be. 4 Aware of its weakness the ego wants your allegiance, but not as you really are. 5 The ego therefore wants to engage your mind in its own delusional system, because otherwise the light of your understanding would dispel it. 6 It wants no part of truth, because the ego itself is not true. 7 If truth is total, the untrue cannot exist. 8 Commitment to either must be total; they cannot coexist in your mind without splitting it. 9 If they cannot coexist in peace, and if you want peace, you must give up the idea of conflict entirely and for all time. 10 This requires vigilance only as long as you do not recognize what is true. 11 While you believe that two totally contradictory thought systems share truth, your need for vigilance is apparent.