Ad Petri Cathedram §140

¹⁴⁰ There is one truth especially which We think is self-evident: when the sacred rights of God and religion are ignored or infringed upon, the foundations of human society will sooner or later crumble and give way. Our predecessor of immortal memory, Leo XIII, expressed this truth well: "It follows . . . that law becomes ineffective and all authority is weakened once the sovereign and eternal rule of God, who commands and forbids, is rejected." (66) Cicero expressed the same idea when he wrote, "You, the priests, are protecting Rome with religion more effectively than she is protected with walls." (67)