Whatever we do, whether good or bad, increases in us more and more. If one day a person thinks about music for five minutes, the next day that thought will continue for half an hour. If one day he thinks about poetry for ten minutes, the next day that thought will continue for an hour. If a person has a little thought of bitterness, unconsciously the thought will grow until his mind is full of bitterness. Every sin comes about in this way. Zarathustra distinguishes three kinds of sin: the sin of thought, the sin of speech and the sin of action. To have a thought of bitterness, the thought of evil, is like doing evil; to speak evil is like doing evil, and when a person commits an evil action, then the evil is concrete.