At the time of the Dreyfus Affair and the start of the Action Française, Charles Maurras pressed forward the idea, borrowed from Auguste Comte, of an alliance between Positivists and Catholics. The compatibility of Maurras’s own Positivist political ideas with Catholic principles was later questioned by Marc Sangnier, and the ensuing polemic between the two men was itself the origin of a lengthy controversy in which the two leading figures were the philosophers Maurice Blondel and Lucien Laberthonnière, both of whom strongly contested Catholic indulgence towards Maurras and the Action Française. This study of Maurrassian ideology and Catholic reactions to it explores a wide range of themes. They include the posterity of Comte’s Positivism, anti-semitism at the turn of the twentieth century, the absolutism and romanticism of Maurras’s nationalism, the crucial importance of the separation of Church and State for the somewhat fortuitous identification of the Action Française with the cause of Rome, and the confrontation of Maurras’s idea of the Roman Church with the Christian ideals upheld by Blondel and Laberthonnière.