By proclaiming man’s absolute autonomy in the intellectual, moral and social order, Liberalism denies, at least practically, God and supernatural religion. If carried out logically, it leads even to a theoretical denial of God, by putting deified mankind in place of God. It has been censured in the condemnations of Rationalism and Naturalism. The most solemn condemnation of Naturalism and Rationalism was contained in the Constitution “De Fide” of the Vatican Council (1870); the most explicit and detailed condemnation, however, was administered to modern Liberalism by Pius IX in the Encyclical “Quanta cura” of 8 December, 1864 and the attached Syllabus.
[See the full post at: Roman Catholic view on Liberalism-Hermann Gruber (1913)]