Martin Luther and John Calvin were the principal ‘magistral’ Reformers of the sixteenth-century: they sought to enlist the cooperation of rulers in the work of reforming the Church. However, neither regarded the relationship between Reformed Christians and the secular authorities as comfortable or unproblematic. The two pieces translated here, Luther's On Secular Authority and Calvin’s On Civil Government, constitute their most sustained attempts to find the proper balance between these two commitments. Despite their mutual respect, there were wide divergences between them. Luther’s On Secular Authority would later be cited en bloc in favour of religious toleration, whereas Calvin envisaged secular authority as an agency for the compulsory establishment of the external conditions of Christian virtue and the suppression of dissent. The introduction, glossary, chronology and bibliography contained in this volume locate the texts in the broader context of the theology and political thinking of their authors.