According to Roger Caillois, play is "an occasion of pure waste: waste of time, energy, ingenuity, skill, and often of money." In spite of this--or because of it--play constitutes an essential element of human social and spiritual development. In this classic study, Caillois defines play as a free and voluntary activity that occurs in a pure space, isolated and protected from the rest of life. Play is uncertain, since the outcome may not be...