The liturgy of the medieval church has been little studied in its relation to medieval thought and society. It has often been taken for granted that the Latin liturgy was understood by the priest, but to his congregation was only a spectacle of authority. This book begins with the hypothesis that the liturgy was, in some senses, understood by its congregations, and it attempts to discover what this understanding might have been. Through studies of the sermons and writings of Tertullian, Ambrose, Augustine, Bede, Abelard and others, of the practice of infant baptism, and of the art and architecture of the baptistery, the book attempts to rediscover the underlying philosophy of symbol which is the grounds of ritual understanding in both priest and congregation.