This volume, which has developed out of a 2011 colloquy held at the University of Geneva to commemorate the quincentenary of Pierre Viret, has among its aims the consideration of Viret as a reformer in his own right, rather than a populariser of Calvin, or a minor and local figure. Its eighteen essays bring together contributors from France, Switzerland, Belgium and the USA, writing in both French and English (short translated summaries are provided at the end of each essay). The collection is divided into two sections of nine essays each, the first addressing elements of Viret's thought and writings, and the other his active career as a reformer in Lausanne, France and Béarn. As the subtitle suggests, the relationship between the two sections, between thought and action, emerges as an important theme in the collection. Viret's writings on religious practice come under repeated attention, from Lee Palmer Wandel's essay on Viret's conception of the eucharist, and Olivier Millet's discussion of his homiletics, to his early, and uncompromising, anti-Nicodemite stance, which Carlos Eire suggests had developed into an implicit resistance theory by the early 1560s. Another recurring point is Viret's often nuanced approach to the description of other religious traditions. As separate papers by Frédéric Amsler, Irena Backus and Karine Crousaz discuss, his descriptions of the Catholic Church often used classical and early Christian sources, and he took great interest in comparing the origins of Catholic and pagan customs, as well as what he saw as Turkish toleration and rejection of images. These comparisons were developed as criticism of the Catholic Church, but Viret's willingness to discuss them seriously leads Olivier Pot to suggest that they can represent an early form of comparative religious studies. As Crousaz and Camillocci write in their introduction, Viret's interest in connecting his writing to the world of the common man, and to the practical consequences of reform, makes him a particularly interesting subject for historians studying the religious and popular cultures of the Reformation. This volume unites consideration of Viret in Lausanne, where his work in shaping the church is considered by, amongst others, Geneviève Gross, Claire Moutengou Barats and James J. Blakeley alongside that of farther-flung areas. These include Béarn, where Philippe Chareyre discusses Viret's final challenge, or the areas towards the Rhineland, which Michael Bruening suggests was at one time as important to Viret, Calvin and Farel's network as were the churches in France.