In June 1846, in an Italy divided by the Congress of Vienna, the election of Pius IX gives neo-Guelfists an opportunity to reconsider the question of Italian unity. In October 1847, on the eve of Roman and Parisian revolutions, Alphonse de Lamartine, who has complex and ambivalent relationships with religion, rejects the neo-Guelfist solution and justifies himself with a long and intense criticism of the temporel power of the papacy. Through the detailed analysis of Lamartinian criticism, and within the scope of the history of Roman Curia from the French victory in Italy to the accession of Pius IX (1796-1846), I examine what Lamartine presents as the two vices of the papal government: its complexity and its instability – that is to say, the questions of its nature and of the continuity of its power.