This chapter examines the religious choices of Félicité Lamennais, a key figure in the political and religious debates of the French Restoration. After flirting with the doctrines of Rousseau as an adolescent, Lamennais converted to ultramontane Catholicism, convinced that papal authority was the only reliable basis for social order. State repression of Catholicism in Poland, Belgium, Ireland, and France in 1830 led Lamennais to alter his views and embrace a marriage of “God and Liberty” in which Catholics would support the separation of church and state, and defend political and civil liberties, in particular the freedom of the press. Twice condemned by Pope Gregory XVI, Lamennais abandoned Catholicism and embraced the right of freedom of conscience that he had formerly condemned.