It is perhaps advisable in opening this chapter to explain what is meant by the term “Play Theory.” A play theory is a scientific attempt to answer the query, “What is Play?” In our country we have accepted the phenomenon without much inquiry as something inevitable, and in the nature of original sin; elsewhere play has been called many things from “a system of ideographic hieroglyphs” to “the first poetry of the human soul.” The play theory, however, has a task beyond defining play, and is concerned with the answer of a further perplexing question, “Why do children play?”