 On philosophical ground, he struggled with unwavering hope against Naturalism and Liberalism, which he considered a fatal impediment to the constitution of an unreservedly Christian society.He helped, in a measure, to prepare men's minds for the definition of the papal infallibility, a dogma which reversed the struggle against papal authority fought a century previously by many Gallican and Josephite bishops.On both the occasion of the definition of the Immaculate Conception (1854) and on that of Papal Infallibility (1870), Guéranger contributed written works that served to uphold the Holy See in making these ex cathedra pronouncements.