[Chapter 7, The Parable of a Magic City,] has two distinct parts. The first is a story of the previous existence of a Buddha called Great-Universally-Excelling-Wisdom. The second consists of the parable for which this chapter is named, “The Magic City.” The concept of previous existences is a fundamental teaching in Buddhism. Its rationale is that there must be some prior meaning or conditions before something else can come into existence. (Nothing comes from nothing, and nothing takes place without a cause.) The story of a previous life here refers to a particular incident in the past which has led to the emergence of a present situation—that is, the origin of things. In the Lotus Sutra, Sakyamuni is said to employ three methods of expounding the law: logical explanations, parables, and stories of previous lives.
Introduction to the Lotus Sutra