Traditional theories of play have either reduced it to an unreal, unusual activity akin to religious rituals or art, or to preparatory, simulated learning behavior for real social activities involving competition and rules. However, play is a unique way of living and acting in the midst of real life, just like sleeping, eating, or working. What distinguishes the structure of play—hide-and-seek, seesaws, toys, make-believe—from the structure of projects—magic rituals, tools, theater, sports? This book offers a unique theory of play, developing this question from a bodily perspective.