In this Habilitationsschrift (Kirchliche Hochschule Wuppertal/Bethel), Christopher Voigt-Guy examines Martin Luther's theology of ecclesiastical offices in the context of the Middle Ages. Following the lead of Berndt Hamm, among others, Voigt-Guy provides a rich historical context for Luther's theology and emphasises the great diversity of medieval understanding(s) of church offices and their functions. (Voigt-Guy pays special attention to Gratian, Aquinas, Gerson and Biel.) Luther's Amtstheologie represents a significant change and new orientation in the history of theology, but this revolution was not driven by the reformer's famous ‘priesthood of all believers’. Voigt-Guy emphasises throughout that this doctrine was a byproduct of a much more fundamental conviction that may be found in Luther's earliest lectures – faith as the defining centre of the homo spiritualis. Voigt-Guy demonstrates how the possession and nurturing of faith quickly became absolutely central to the early Luther's thinking about Church and church offices – everything was ordered to this end. Luther's early Amtstheologie was a theology of faith. This emphasis on faith had a spiritualising, subjectivising and individualising effect on Luther's theology of the Church and its offices, and from the perspective of late medieval Catholicism it constituted ‘einen theologischen Affront’ (p. 103), as it directly challenged notions of external authority (auctoritas) and order (ordo). (One of the more interesting suggestions in Voigt-Guy's study is that this spiritualising impulse had it origins in Luther's monastic context.) But Luther's Amtstheologie continued to evolve into the early 1520s. When confronted with the challenges of so-called radicals such as Andreas Bodenstein von Karlstadt and Thomas Müntzer, Luther placed a much stronger emphasis on the external and objective character of the Church, its offices and its means of grace (thus largely undermining lay initiative), even as he continued to stress the essential parity between clergy and laity and the centrality of faith as the constitutive element in the Christian life. According to Voigt-Guy, the result was a new late medieval type of Church (Kirchentypus) that had both important continuities and discontinuities with the medieval heritage. Potestates und ministerium publicum is a sophisticated, demanding and persuasive account of Martin Luther's theology of ecclesiastical offices.