In 1925 Pope Pius XI issued his encyclical Quas Primas, which established the Feast of Christ the King and taught the moral obligation of all nations to reverence the kingship of Christ over all the world. The reverence is due not only by Catholic countries, but by all men, whether baptized or not, and applies equally to governments as to individuals. The pope wrote: "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...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...With God and Jesus Christ 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"  In this teaching, Pius reaffirms the traditional Catholic teaching of the social kingship of Christ. This principle underlay the whole social and political edifice of the Middle Ages known as "Christendom", and it is this teaching which has been subsequently lost or denied in the modern world.