19 Not less deplorable are the injuries which accrue from this negation to the moral life of individuals and of civil society. Take away the principle that there is anything divine outside this visible world, and you take away all check upon unbridled passions even of the lowest and most shameful kind, and the minds that become slaves to them riot in disorders of every species. "God gave them up to the desires of their heart, unto uncleanness, to dishonor their own bodies among themselves" ( Rom . i. 24). You are well aware, Venerable Brethren, how truly the plague of depravity triumphs on all sides, and how the civil authority wherever it fails to have recourse to the means of help offered by the supernatural order, finds itself quite unequal to the task of checking it. Nay, authority will never be able to heal other evils as long as it forgets or denies that all power comes from God. The only check a government can command in this case is that of force; but force cannot be constantly employed, nor is it always available yet the people continue to be undermined as by a secret disease, they become discontented with everything, they proclaim the right to act as they please, they stir up rebellions, they provoke revolutions, often of extreme violence, in the State; they overthrow all rights human and divine. Take away God, and all respect for civil laws, all regard for even the most necessary institutions disappears; justice is scouted; the very liberty that belongs to the law of nature is trodden underfoot; and men go so far as to destroy the very structure of the family, which is the first and firmest foundation of the social structure. The result is that in these days hostile to Christ, it has become more difficult to apply the powerful remedies which the Redeemer has put into the hands of the Church in order to keep the peoples within the lines of duty.
Source: Iucunda Sane (Vatican.va)