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Michael Servetus (1553)

The turning point in Calvin's fortunes occurred when Michael Servetus, a brilliant Spanish polymath who introduced the Islamic idea of pulmonary circulation to Europe, and a fugitive from ecclesiastical authorities, appeared in Geneva on 13 August 1553. Servetus was a fugitive on the run after he published The Restoration of Christianity (1553), Calvin scholar Bruce Gordon commented "Among its offenses were a denial of original sin and a bizarre and hardly comprehensible view of the Trinity."

Decades earlier, in July 1530 he disputed with Johannes Oecolampadius in Basel and was eventually expelled. He went to Strasbourg, where he published a pamphlet against the Trinity. Bucer publicly refuted it and asked Servetus to leave. After returning to Basel, Servetus published Two Books of Dialogues on the Trinity (Latin: Dialogorum de Trinitate libri duo) which caused a sensation among Reformers and Catholics alike. When John Calvin alerted the Inquisition in Spain about this publication, an order was issued for Servetus's arrest.

Calvin and Servetus were first brought into contact in 1546 through a common acquaintance, Jean Frellon of Lyon; they exchanged letters debating doctrine; Calvin used a pseudonym as Charles d' Espeville and Servetus used the moniker Michel de Villeneuve. Eventually, Calvin lost patience and refused to respond; by this time Servetus had written around thirty letters to Calvin. Calvin was particularly outraged when Servetus sent him a copy of the Institutes of the Christian Religion heavily annotated with arguments pointing to errors in the book. When Servetus mentioned that he would come to Geneva, "Espeville" (Calvin) wrote a letter to Farel on 13 February 1546 noting that if Servetus were to come, he would not assure him safe conduct: "for if he came, as far as my authority goes, I would not let him leave alive."

In 1553 Servetus published Christianismi Restitutio (English: The Restoration of Christianity), in which he rejected the Christian doctrine of the Trinity and the concept of predestination. In the same year, Calvin's representative, Guillaume de Trie, sent letters alerting the French Inquisition to Servetus. Calling him a "Spanish-Portuguese", suspecting and accusing him of his recently proved Jewish converso origin. De Trie wrote down that "his proper name is Michael Servetus, but he currently calls himself Villeneuve, practicing medicine. He stayed for some time in Lyon, and now he is living in Vienne." When the inquisitor-general of France learned that Servetus was hiding in Vienne, according to Calvin under an assumed name, he contacted Cardinal François de Tournon, the secretary of the archbishop of Lyon, to take up the matter. Servetus was arrested and taken in for questioning. His letters to Calvin were presented as evidence of heresy, but he denied having written them, and later said he was not sure it was his handwriting. He said, after swearing before the holy gospel, that "he was Michel De Villeneuve Doctor in Medicine about 42 years old, native of Tudela of the kingdom of Navarre, a city under the obedience to the Emperor". The following day he said: "..although he was not Servetus he assumed the person of Servet for debating with Calvin". He managed to escape from prison, and the Catholic authorities sentenced him in absentia to death by slow burning.

On his way to Italy, Servetus stopped in Geneva to visit " d'Espeville ", where he was recognized and arrested. Calvin's secretary, Nicholas de la Fontaine, composed a list of accusations that was submitted before the court. The prosecutor was Philibert Berthelier, a member of a libertine family and son of a famous Geneva patriot, and the sessions were led by Pierre Tissot, Perrin's brother-in-law. The libertines allowed the trial to drag on in an attempt to harass Calvin. The difficulty in using Servetus as a weapon against Calvin was that the heretical reputation of Servetus was widespread and most of the cities in Europe were observing and awaiting the outcome of the trial. This posed a dilemma for the libertines, so on 21 August the council decided to write to other Swiss cities for their opinions, thus mitigating their own responsibility for the final decision. While waiting for the responses, the council also asked Servetus if he preferred to be judged in Vienne or in Geneva. He begged to stay in Geneva. On 20 October the replies from Zurich, Basel, Bern, and Schaffhausen were read and the council condemned Servetus as a heretic. The following day he was sentenced to burning at the stake, the same sentence as in Vienne. Some scholars claim that Calvin and other ministers asked that he be beheaded instead of burnt, knowing that burning at the stake was the only legal recourse. This plea was refused and on 27 October, Servetus was burnt alive at the Plateau of Champel at the edge of Geneva.