 One of Campanella’s most important works is Atheismus triumphatus (Atheism Conquered), written between 1606 and 1607. He himself regarded it as a watershed in his thinking, signaling his detachment from the more openly rationalist positions of his youth and his move toward a more sincere adherence to Christian principles. In letters written from prison, he describes the work as a “volume against politicians and Machiavellians” (Lettere, p. 26). Central to the work is his polemic against both reason of state and Machiavelli’s conception of religion as a political invention, a useful “fiction” devised by priests and princes to gain and maintain power. This polemic is coupled with the need to undertake a far-reaching rational examination, passing in review and evaluating all religious beliefs and philosophical doctrines in order to demonstrate that religion, in contrast to what politicians think, is a “natural virtue” inborn in human beings. A further motive of this research is to ascertain the relationship between natural religion and Christianity, which leads to the conclusion that there is no conflict between Christian law and natural law but instead a profound and fundamental agreement, since Christ did not nullify and abolish natural law but rather added to it moral precepts and rites that completed and perfected it.