In order to train the ego it is necessary that one should distinguish what is the right of the ego and what is not its right. The ego has a tendency to want what it needs and also what it does not need. The first is its natural appetite and the second is greed. This is like the nature of the dog, that after eating the flesh off a bone still guards the bone against another dog. Besides this the ego has a tendency to want more and more of what it likes, regardless of right and justice, also regardless of the after-effect.