Quote from A Course in Miracles Text Chapter 22 - SALVATION AND THE HOLY RELATIONSHIP.

T-22.III.1. The introduction of reason into the ego's thought system is the beginning of its undoing, for reason and the ego are contradictory. 2 Nor is it possible for them to coexist in your awareness. 3 For reason's goal is to make plain, and therefore obvious. 4 You can see reason. 5 This is not a play on words, for here is the beginning of a vision that has meaning. 6 Vision is sense, quite literally. 7 If it is not the body's sight, it must be understood. 8 For it is plain, and what is obvious is not ambiguous. 9 It can be understood. 10 And here do reason and the ego separate, to go their separate ways.