Quote from ACIM Text Chapter 4, Section 3 - The Ego and False Autonomy.

The ego literally lives by comparisons. Equality is beyond its grasp, and charity becomes impossible. The ego never gives out of abundance, because it was made as a substitute for it. That is why the concept of "getting" arose in the ego's thought system. Appetites are "getting" mechanisms, representing the ego's need to confirm itself. This is as true of body appetites as it is of the so-called "higher ego needs." Body appetites are not physical in origin. The ego regards the body as its home, and tries to satisfy itself through the body. But the idea that this is possible is a decision of the mind, which has become completely confused about what is really possible.