These two public letters are Calvin’s first publication for a wider audience since his arrival in Geneva. Its preface is dated on 12 January 1537. After years of scholarly activity and travelling in anonymity Guillaume Farel forcefully committed him to the church of Geneva. The young author of the Institutes (1536) was at Farel’s and Viret’s side at the Disputation of Lausanne. He broke any allegiance with the Circle of Meaux and sided wholeheartedly with the reformed cause. The contents of the Epistolae duae, drafted in Ferrara, reveal that Calvin must have revised the manuscript to give testimony to the appeal of the Disputation to the roman catholic clergy. The first letter challenges Christians to break away for idolatry and confess publicly. The second letter is a challenge to the clergy either to reform or lay down their offices. The Epistolae duae are the opening move in the exchange among the reformers on nicodemism. Calvin, as ghost writer of Farel, breaks with the reform movement of Meaux, France. That was what the reformed position in October 1536 had implied. Calvin’s two minor contributions to the Disputation of Lausanne have been added to the present edition.