Martin Bucer’s theology is perhaps the most diffi cult of all the major reformers to characterize because of its evolving nature. Although there are certainly fundamental features that remained constant through his career, what makes Bucer so unusual and so fascinating is the evolution of his thought as he worked out the implications of those fundamental beliefs and their specifi c applications over his years of experience as pastor, teacher and church organizer. One of the areas in which Bucer changed over the course of his career was his use of the church fathers. Both Pierre Fraenkel and Robert Stupperich have pointed to a similar pattern in Bucer’s citations from the church fathers and from canon law: a few references during the 1520s, growing frequency from about 1530, and signifi cant use by the end of the 1530s.1 As an illustration of this general development, Irena Backus has emphasized the visible role Bucer gave the Fathers in his 1536 Romans commentary, a striking change from his tacit use of them in the three editions of his John commentary.2 Bucer’s greater willingness to cite the Fathers in defense of reform is evident already in his 1534 Defensio adversus Axioma Catholicum, as the recently published critical edition of this work makes clear. His involvement in imperial politics and the discussions with Catholic theologians associated with the religious colloquies, however, led to a new emphasis particularly on the institutions of the early church as a model for the reformed (small r) and catholic (small c) church.3 The Florilegium Patristicum that he began to assemble around this time contains excerpts from the Fathers that deal primarily with practical institutional issues such as church government, church discipline, and the proper ordering of ecclesiastical rites. In comparison to work done on Bucer’s early career, little attention has been paid to the role of the early church in Bucer’s works from the 1540s. This would be a major undertaking, far beyond the scope of a single article. This paper will therefore examine one aspect of Bucer’s use of the Fathers from this period by focusing attention on a major work from that decade, the Bestendige Verantwortung or Steadfast Defense of the Cologne reformation ordinance. The Steadfast Defense cannot be separated from the circumstances in which it was written, as part of an extended debate with the Catholic theologian Johannes Gropper over the attempted reformation of Cologne. Both Bucer and Gropper had been key players in the religious colloquy of Worms in 1540 and had together produced the draft of the Regensburg Book which served as the basis for discussion during that religious colloquy in 1541.4 Bucer’s involvement in these colloquies prompted the archbishop of Cologne, Hermann von Wied, to invite the Strasbourg reformer to assist when he decided to undertake a ‘Christian Reformation’ of his territory on his own initiative.5 The archbishop assumed that Bucer and Gropper would continue their partnership, but Gropper was adamantly opposed to Bucer’s presence in the territory, and he quickly became the spokesman 1. Pierre Fraenkel, ‘Introduction’, Martini Buceri Opera Latina (Paris/Leiden: E.J. Brill, 1954–, henceforth BOL), 3, xviii; Robert Stupperich, ‘Martin Bucer’s Gebrauch des canonischen Rechts’, in Marijn de Kroon and Marc Lienard (eds.), Horizons Européens de la Réforme en Alsace. Das Elsaβ und die Reformation im Europea des 16. Jahrhunderts. Aufsätze zum 65. Geburtstag von Jean Rott (Société Savante d’Alsace et des Régions de l’Est, Collection ‘grandes Publications’, 17; Strasbourg: Istra, 1980), pp. 241–52. 2. ‘Ulrich Zwingli, Martin Bucer and the Church Fathers’, in Irena Backus (ed.), The Reception of the Church Fathers in the West From the Carolingians to the Maurists (Studies in the History of Christian Thought; Leiden: E.J. Brill, 1997), 2, pp. 627–60; see also Irena Backus, ‘Martin Bucer and the Patristic Tradition’, in Christian Krieger and Marc Lienhard (eds.), Martin Bucer and Sixteenth Century Europe. Actes du colloque de Strasbourg (28–31 août 1991) (Studies in Medieval and Reformation Thought, 52; Leiden: E.J. Brill, 1993), 1, pp. 55–69. 3. Cornelis Augustijn, ‘Bucer und die Religionsgespräche von 1540/41’, in Martin Bucer and Sixteenth Century Europe, 2, pp. 671–80. 4. See the introduction to the ‘Wormser Buch’, Martin Bucers Deutsch Schriften (Gütersloh: Mohn, 1960–, henceforth BDS), 9/1, pp. 323–30, and the literature cited there. 5. On the Cologne Reformation, the most detailed account is still Conrad Varrentrop, Hermann von Wied und sein Reformationsversuch in Köln. Ein Beitrag zur detuschen Reformationsgeschichte (Leipzig: yon Duncker & Humblot, 1878), supplemented by the discussion of Bucer’s role, with related documents, in J.-V. Pollet, Martin Bucer, Études sur les relations de Bucer avec les Pays-Bas, l’Électorat de Cologne et l’Allemagne du Nord, avec de nombreux textes inédits (Studies in Medieval and Reformation Thought, 33–34; Leiden: E.J. Brill, 1985), 1, pp. 83–234 and 2, pp. 35–162; see also Marlin de Kroon, ‘Bucer und die Kölner Reformation’, in Martin Bucer and Sixteenth Century Europe, 2, pp. 493–506.