Why were sixteenth-century Europeans willing to risk their lives to attack 'mere matter' - images, lamps, altars, vestments? The most influential medieval liturgical commentary, William Durand's Rationale divinorum officiorum, offers an answer. Reading Durand to excavate the meaning of churches, altars, vestments, this book reveals the stunning scope of Reformation reconceptualization of worship, time, and matter. For Durand, liturgy was an ongoing praxis in which Scripture and Creation were in constant dialogue, leading to an ever-richer understanding of divine revelation. In attacking the made world - what human beings had fashioned from prime matter - Protestants sundered Creation from the liturgy and fundamentally changed how liturgy was understood, and what both Protestants and Catholics held the relationship between divine revelation and matter to be. Altars and vestments became 'objects' to which human beings gave meaning. As the sixteenth century redefined liturgy as a verbal practice, time, matter, and worship were realigned.