Alister McGrath writes in his survey of the history of Protestantism, Christianity’s Dangerous Idea, 90–91:
[John Calvin’s] rise to prominence began in September 1536. The city of Lausanne was debating whether to follow Geneva and accept the principles of the Reformation. Farel and Viret traveled to Lausanne, bringing Calvin with them, to take part in the public disputation that was now an invariable part of the decision-making process. They were pitted against the local clergy, who were not noted for their academic distinction. The debate was not going well for Farel and Viret, who found themselves severely challenged by some of the questions they were forced to address.
One of those questions went to the heart of the reforming program at Geneva and raised the specter of Anabaptism. Were not Viret and Farel allowing people to interpret the Bible as they pleased, without taking the view of the early church writers seriously? It was a moment of tension; the debate was in the balance. The credibility of the reformation at Geneva would be permanently damaged if any association was made with the radical cause and the social instability it was widely believed to engender. Calvin rose to answer.
Apparently quoting early Christian writers from memory, Calvin insisted that he and his colleagues took them with the greatest of seriousness and saw them as authorities of significance. The audience was dazzled by the brilliance of Calvin’s presentation: he quoted the third-century writer Cyprian of Carthage to the letter (“in the second book of his letters, the third letter”) and the fourth-century theologian and preacher John Chrysostom even more precisely (“the twenty-first homily, about halfway through”). By the time Calvin sat down, everyone was clear on two things: the Genevan Reformation was about the renewal and continuity of the church, and a new star had arisen in the Protestant firmament. Lausanne was won over to the Reformation, while Geneva was won over to Calvin.