One of the aims of this book is to call the attention of philosophers of religion to the importance of religious practice and to demonstrate how rich a topic this is for philosophical reflection. Another aim is to show liturgical scholars who are not philosophers that a philosophical approach to liturgy casts an illuminating light on the topic that supplements their own approach. Insofar as philosophers have written about liturgy, they have focused most of their attention on its formative and expressive functions. This book focuses instead on understanding what liturgical agents actually do. It is what they do that functions formatively or expressively. What they do is basic.