I use liminality in the sense defined by Victor Turner in Process, Performance, and Pilgrimage (New Delhi: Concept, 1979) esp. pp. 11–59. Also see Jonathan Z. Smith, “Birth Upside Down or Right Side Up?” History of Religions 9 (1969–1970), pp. 281–303, and his “A Place on Which to Stand: Symbols and Social Change,” Worship 44 (1970), pp. 457–474.