5 For, indeed, although the socialists, stealing the very Gospel itself with a view to deceive more easily the unwary, have been accustomed to distort it so as to suit their own purposes, nevertheless so great is the difference between their depraved teachings and the most pure doctrine of Christ that none greater could exist: "for what participation hath justice with injustice or what fellowship hath light with darkness?"(7) Their habit, as we have intimated, is always to maintain that nature has made all men equal, and that, therefore, neither honor nor respect is due to majesty, nor obedience to laws, unless, perhaps, to those sanctioned by their own good pleasure. But, on the contrary, in accordance with the teachings of the Gospel, the equality of men consists in this: that all, having inherited the same nature, are called to the same most high dignity of the sons of God, and that, as one and the same end is set before all, each one is to be judged by the same law and will receive punishment or reward according to his deserts. The inequality of rights and of power proceeds from the very Author of nature, "from whom all paternity in heaven and earth is named."(8) But the minds of princes and their subjects are, according to Catholic doctrine and precepts, bound up one with the other in such a manner, by mutual duties and rights, that the thirst for power is restrained and the rational ground of obedience made easy, firm, and noble.
Source: Quod Apostolici Muneris (Vatican.va)