Knox disembarked in Dieppe, France, and continued to Geneva, where John Calvin had established his authority. When Knox arrived Calvin was in a difficult position. He had recently overseen the Company of Pastors, which prosecuted charges of heresy against the scholar Michael Servetus, although Calvin himself was not capable of voting for or against a civil penalty against Servetus. Knox asked Calvin four difficult political questions: whether a minor could rule by divine right, whether a female could rule and transfer sovereignty to her husband, whether people should obey ungodly or idolatrous rulers, and what party godly persons should follow if they resisted an idolatrous ruler. Calvin gave cautious replies and referred him to the Swiss reformer Heinrich Bullinger in Zürich. Bullinger's responses were equally cautious; but Knox had already made up his mind. On 20 July 1554, he published a pamphlet attacking Mary Tudor and the bishops who had brought her to the throne. He also attacked the Holy Roman Emperor, Charles V, calling him "no less enemy to Christ than was Nero".