In this paper the author proposes a hypothesis of the origin of theater, tracing it to the ritual enactment of a primal phantasy of the birth of the subject as a separate entity which breaks off from a primordial One. This is experienced as a violent and traumatic moment, and its repeated reenactment in theater attempts a reworking of the early anxieties of separateness. Boundaries (on multiple levels) are thereby consolidated but also abolished in order to make new constructions possible. The subject, in the theatrical act (theoria), is a spectator of alterity, of the familiar but estranged (Unheimliche), of the absent Other, and ultimately, of nothingness. Theater, viewed in this perspective, is an activity in the service of symbol formation and of the creation of theories of meaning. The mise-en-scène aims at a mise-en-sens.