Calvin's doctrines and theology created profound changes within the fledgling Protestant churches. In particular, Calvin led Protestantism to insert itself into state control and secular affairs, and his ideas about salvation and whether it is predestined by God or open to all, are still debated in contemporary times.John Calvin (1509-1564), a French theologian, brought profound changes to the Reformation. By 1530, he had become an aggressive advocate of Protestantism, and in 1536, Calvin went to Geneva to help the city split from the Roman Catholic Church. However, Calvin's reforms were not welcome by those in power, and he fled the city in 1538. Upon his return in 1541, he instituted radical reform into church structure and exerted religious authority over the state. His reforms quickly became known as Calvinism and spread throughout Europe, where they heavily influenced Protestant reforms.