Yet 1539 was a turning point for Calvin. In that year he completed the first of his commentaries on books of the Bible, a commentary on Paul’s letter to the Romans. He also published the first major revision of his Institutes of the Christian Religion, moving it from being an introduction to basic Christianity toward being a full systematic theology. Both of these works pointed to his developing interests and insights. But a third work that he wrote that year is the most important as an introduction to the life and thought of Calvin. This work is his famous treatise known as “Reply to Sadoleto.”

Calvin’s treatise was a response to a sharp attack on the Reformation written by Jacopo Sadoleto. Sadoleto was a bishop and cardinal of the Roman Catholic Church and a distinguished scholar. After hearing of the exile of Calvin and other pastors, he wrote to the Genevans in 1538 urging them to return to the old church. While the Genevan authorities did not regard Sadoleto’s letter as a real threat to the Protestant establishment in Geneva, they did want a strong and effective response written to it. After careful consideration they finally realized that their former pastor Calvin, whom they had exiled, was the best equipped to write the answer they wanted.

Calvin must have received their request with some amusement and satisfaction. Their recognition that they needed him surely made Calvin feel vindicated. He saw the importance of the task and quickly set to work writing his “Reply to Sadoleto.” He completed the treatise in six days. Theodore Beza wrote that the work was full of “truth and eloquence.”¹ More recent scholars have evaluated the treatise as one of the most powerful defenses of the Reformation ever written.

Calvin’s “Reply to Sadoleto” is important for more than its brilliant defense of Reformed Christianity. It is also a window into Calvin’s soul. Calvin was usually very reticent to write much about himself, but in this work there is a remarkable personal quality that reveals a great deal about him.

By nature Calvin was a very private person. In few of his works does he write about himself. Even in his letters he does not become introspective or discuss the events of his personal life in much detail. But in “Reply to Sadoleto” he reveals indirectly a good deal of his own experience of the Reformation and the key motivations of his life. These experiences and convictions of his life are also key elements of the religion he taught as a pastor.

The character of Sadoleto’s appeal to the Genevans provided several incentives for Calvin to show something of his own experience in his reply. First, Sadoleto made a very personal attack on Calvin and the other ministers, saying that they had been motivated in their reforming work only by a desire for fame and money. Second, Sadoleto argued that only the Roman Catholic Church possessed truth, certainty, and salvation—issues of deep personal significance for Calvin. Third, Sadoleto had created several prayers in his treatise that he had put in the mouths of an imagined person to illustrate some of the points he was making. These prayers written in the first person evoked from Calvin a response written in the same language. This literary device was well known to Calvin who was acquainted with it from the writings of Quintilian, the ancient teacher of rhetoric, and had been commented on by Calvin in his early commentary on Seneca: