Hall classifies dreams into five principles. The first is self-concepts which refer to the number and types of roles one plays in one's dreams. The second concept concerns others. This mentions the roles that others play in your dream and how you interact with them. World concepts are the third principle. This represents the surrounding dreams and landscape. Hall believes this concept describes how one sees the world. The fourth concerns the concepts of impulses, prohibitions and sanctions. This concept refers to how behavior is governed by both impulses and punishments. The last concept is the concepts of problems and conflicts. This concept symbolizes the struggles and difficulties of waking life. Hall believes that by using all five concepts one is able to evaluate the content of dreams and better understand the unconscious mind (Dream Theories,