John Calvin (1509– 1564), a Frenchman, was the most important systematic theologian of the Protestant Reformation. Institutes of the Christian Religion was the first effort to form the ideas of Protestant theologians from Martin Luther (1483– 1546) onward into a complete system of Christian theology that would challenge the theology of the Catholic Church. The first edition appeared in 1536, shortly after Calvin had left France as the result of a government crackdown on Protestants. Calvin sought a broad audience and, despite his own experience, hoped that the work would be instrumental in the conversion of France to Protestantism; the first edition appeared with a prefatory letter to the French king, Francis I, in ultimately fruitless hopes of winning him to the Protestant cause. The work was published in Latin, the language of professional theologians and philosophers. Subsequent editions appeared in Latin in 1539, 1543, and 1559, respectively translated into French in 1541, 1545, and 1560. It became the authoritative work of the tradition of Reformed or “Calvinist” Protestantism and influenced many other Protestant branches as well.