Il Fermo Proposito §9

⁹ In passing it is well to remark that it is impossible today to re-establish under the same form all the institutions which have been useful and even the only effective ones in past centuries, so numerous the new needs which changing circumstances keep producing. But the Church in its long history and on every occasion has wisely shown that she possesses the marvelous power of adapting herself to the changing conditions of civil society. Thus, while preserving the integrity and immutability of faith and morals and upholding her sacred rights, she easily bends and accommodates herself to all the unessential and accidental circumstances belonging to various stages of civilization and to the new requirements of civil society.