Diuturnum §17

¹⁷ And if these precepts protect the State, all cause or desire for seditions is removed; the honor and security of rulers, the quiet and wellbeing of societies will be secure. The dignity also of the citizen is best provided for; for to them it has been permitted to retain even in obedience that greatness which conduces to the excellence of man. For they understand that, in the judgment of God, there is neither slave nor free man; that there is one Lord of all, rich "to all that call upon Him,"(21) but that they on this account submit to and obey their rulers, because these in a certain sort bring before them the image of God, "whom to serve is to reign."