Félicité Robert de La Mennais was a French Catholic priest, philosopher and political theorist. He was one of the most influential intellectuals of Restoration France. Lamennais is considered the forerunner of liberal Catholicism and social Catholicism.
His opinions on matters of religion and government changed dramatically over the course of his life. He initially held rationalistic views, but in part due to the influence of his brother, Jean-Marie, came to see religion as an antidote for the anarchy and tyranny unleashed by revolution. He derided Napoleon, in part because of the Organic Articles, in which France acting unilaterally amended the Concordat of 1801 between France and the papacy. Lamennais assailed the Gallican view of the relationship between civil authority and the Church and was for a time a staunch ultramontane.
Lamennais was ordained a priest in 1817, the same year he published Essai sur l'indifférence en matière de religion. In 1830, he founded L'Ami de l'ordre with Montalembert and Lacordaire. His social ideas embraced an enlarged suffrage, separation of church and state, universal freedom of conscience, instruction, assembly, and the press.