All forms of play are transformations of four basic modes by which people know the world: copying, analysis, prediction, and synthesis. Transformation involves foregoing the usual outcomes of adapted intelligence for the sake of voluntary control of one's own behavior in games, and for the excitement of novel affective, cognitive and behavioral variations which then become possible. Imitative play, exploratory play, testing play, and contesting are discussed in terms of their social and personal meanings. Several contesting games enjoyed by children of varying age levels, such as Hide and Seek, Red Rover and Prisoner's Base, are described and classified according to actors, acts, space, and time. Games reflect society in general in that they embody both rule and reason, chance and madness, and societies in particular in that specific types of games enjoyed reflect differing modes of life. It is suggested that the primary function of play may be the enjoyment of a commitment to one's own experience. (NH)