Taken from the encyclical Quas Primas.
14. Let Us explain briefly the nature and meaning of this lordship of Christ. It consists, We need scarcely say, in a threefold power which is essential to lordship. This is sufficiently clear from the scriptural testimony already adduced concerning the universal dominion of our Redeemer, and moreover it is a dogma of faith that Jesus Christ was given to man, not only as our Redeemer, but also as a law-giver, to whom obedience is due. Not only do the gospels tell us that he made laws, but they present him to us in the act of making them. Those who keep them show their love for their Divine Master, and he promises that they shall remain in his love. He claimed judicial power as received from his Father, when the Jews accused him of breaking the Sabbath by the miraculous cure of a sick man. "For neither doth the Father judge any man; but hath given all judgment to the Son." In this power is included the right of rewarding and punishing all men living, for this right is inseparable from that of judging. Executive power, too, belongs to Christ, for all must obey his commands; none may escape them, nor the sanctions he has imposed.
15. This kingdom is spiritual and is concerned with spiritual things. That this is so the above quotations from Scripture amply prove, and Christ by his own action confirms it. On many occasions, when the Jews and even the Apostles wrongly supposed that the Messiah would restore the liberties and the kingdom of Israel, he repelled and denied such a suggestion. When the populace thronged around him in admiration and would have acclaimed him King, he shrank from the honor and sought safety in flight. Before the Roman magistrate he declared that his kingdom was not of this world. The gospels present this kingdom as one which men prepare to enter by penance, and cannot actually enter except by faith and by baptism, which, though an external rite, signifies and produces an interior regeneration. This kingdom is opposed to none other than to that of Satan and to the power of darkness. It demands of its subjects a spirit of detachment from riches and earthly things, and a spirit of gentleness. They must hunger and thirst after justice, and more than this, they must deny themselves and carry the cross.
16. Christ as our Redeemer purchased the Church at the price of his own blood; as priest he offered himself, and continues to offer himself as a victim for our sins. Is it not evident, then, that his kingly dignity partakes in a manner of both these offices?
17. It would be a grave error, on the other hand, to say that Christ has no authority whatever in civil affairs, since, by virtue of the absolute empire over all creatures committed to him by the Father, all things are in his power. Nevertheless, during his life on earth he refrained from the exercise of such authority, and although he himself disdained to possess or to care for earthly goods, he did not, nor does he today, interfere with those who possess them. Non eripit mortalia qui regna dat caelestia.
18. Thus the empire of our Redeemer embraces all men. To use the words of Our immortal predecessor, Pope Leo XIII: "His empire includes not only Catholic nations, not only baptized persons who, though of right belonging to the Church, have been led astray by error, or have been cut off from her by schism, but also all those who are outside the Christian faith; so that truly the whole of mankind is subject to the power of Jesus Christ." Nor is there any difference in this matter between the individual and the family or the State; for all men, whether collectively or individually, are under the dominion of Christ. In him is the salvation of the individual, in him is the salvation of society. "Neither is there salvation in any other, for there is no other name under heaven given to men whereby we must be saved." He is the author of happiness and true prosperity for every man and for every nation. "For a nation is happy when its citizens are happy. What else is a nation but a number of men living in concord?" If, therefore, the rulers of nations wish to preserve their authority, to promote and increase the prosperity of their countries, they will not neglect the public duty of reverence and obedience to the rule of Christ. What We said at the beginning of Our Pontificate concerning the decline of public authority, and the lack of respect for the same, is equally true at the present day. "With God and Jesus Christ," we said, "excluded from political life, with authority derived not from God but from man, the very basis of that authority has been taken away, because the chief reason of the distinction between ruler and subject has been eliminated. The result is that human society is tottering to its fall, because it has no longer a secure and solid foundation."
19. When once men recognize, both in private and in public life, that Christ is King, society will at last receive the great blessings of real liberty, well-ordered discipline, peace and harmony. Our Lord's regal office invests the human authority of princes and rulers with a religious significance; it ennobles the citizen's duty of obedience. It is for this reason that St. Paul, while bidding wives revere Christ in their husbands, and slaves respect Christ in their masters, warns them to give obedience to them not as men, but as the vicegerents of Christ; for it is not meet that men redeemed by Christ should serve their fellow-men. "You are bought with a price; be not made the bond-slaves of men." If princes and magistrates duly elected are filled with the persuasion that they rule, not by their own right, but by the mandate and in the place of the Divine King, they will exercise their authority piously and wisely, and they will make laws and administer them, having in view the common good and also the human dignity of their subjects. The result will be a stable peace and tranquillity, for there will be no longer any cause of discontent. Men will see in their king or in their rulers men like themselves, perhaps unworthy or open to criticism, but they will not on that account refuse obedience if they see reflected in them the authority of Christ God and Man. Peace and harmony, too, will result; for with the spread and the universal extent of the kingdom of Christ men will become more and more conscious of the link that binds them together, and thus many conflicts will be either prevented entirely or at least their bitterness will be diminished.
20. If the kingdom of Christ, then, receives, as it should, all nations under its way, there seems no reason why we should despair of seeing that peace which the King of Peace came to bring on earth - he who came to reconcile all things, who came not to be ministered unto but to minister, who, though Lord of all, gave himself to us as a model of humility, and with his principal law united the precept of charity; who said also: "My yoke is sweet and my burden light." Oh, what happiness would be Ours if all men, individuals, families, and nations, would but let themselves be governed by Christ! "Then at length," to use the words addressed by our predecessor, Pope Leo XIII, twenty-five years ago to the bishops of the Universal Church, "then at length will many evils be cured; then will the law regain its former authority; peace with all its blessings be restored. Men will sheathe their swords and lay down their arms when all freely acknowledge and obey the authority of Christ, and every tongue confesses that the Lord Jesus Christ is in the glory of God the Father."