In the satisfaction of bodily appetites there are two things: Necessity and avidity. A satisfaction which is necessary for existence is one thing, and ever-increasing joy in the satisfaction of bodily appetites is another thing. When man acts regardless of this, in either way, in satisfying the appetites or in abstaining from satisfaction, he makes a mistake. In order to train the ego it is not necessary that cruelty be done to nature; discrimination is necessary, to understand how far one should satisfy the appetites and how far one should refrain from being addicted to such satisfactions.