The most powerful doctrines are the ones we hold as assumptions, moods, 'interpretive keys,' 'lenses,' and the like. The less they are explicitly taught and simply absorbed from one's surroundings, the more powerful and normative they become. One such doctrine I learned early on in my Catholic journey and theological education was a certain way of understanding the relationship between history and eschatology.
It was said that in the past there was too strong a focus on an other-worldly salvation, on an eschatology which was reduced to the four 'last things' (death, judgement, Heaven, hell). This absolved Christians of taking seriously enough the need to serve the salvation and well-being of people in the here and now. But since we modern Christians knew well that we would be judged according to our never-questioned reading of the Judgment scene in Matthew 25, our work was less in preaching, catechizing, 'making disciples of all nations,' but in serving the needs of the 'least of our brothers and sisters.' Our ancestors in the great modern flowering of apostolic religious life did this by finding new forms and building new institutions to serve the needs of people. For us it wasn't to do such things ourselves, but to try to make civil authorities do them instead. This was called the shift from 'charity' to 'justice.' It was one of the great dogmas of my Catholic upbringing.
Now maybe I make a caricature of these things and thus a straw man, but the theological insight behind them is solid; eschatology isn't about a far-away world that renders the current reality less important, but about a Kingdom that is transcendent, always and everywhere present, available, and inviting history into its beatitude.
To reiterate the the basic doctrine: we used to talk about other-worldly salvation, but now we are about peace and justice in the here and now. But here's the funny thing about Christ the King; as an observance, it has journeyed along the opposite trajectory.
The reformed liturgy presents the feast of Christ the King as a celebration of the rule of the cosmic Christ, the alpha and the omega. The day crowns the apocalyptic theme of the last days of Ordinary Time and makes us ready for the similarly apocalyptic first Sunday of Advent. The readings for the Mass and the Divine Office seem to emphasize Christ the King as a day to reflect on the end point of time, history, and God's purpose, without a lot of interference of the messiness of the 'here and now.'
It's funny because the feast of Christ the King used to be a lot more pointed toward the current moment, with much heavier political overtones. Here are a couple of quotes from the encyclical Quas primas of Pius XI, which established the observance:
In the first Encyclical Letter which We addressed at the beginning of Our Pontificate to the Bishops of the universal Church, [Ubi arcano Dei consilio] We referred to the chief causes of the difficulties under which mankind was laboring. And We remember saying that these manifold evils in the world were due to the fact that the majority of men had thrust Jesus Christ and his holy law out of their lives; that these had no place either in private affairs or in politics: and we said further, that as long as individuals and states refused to submit to the rule of our Savior, there would be no really hopeful prospect of a lasting peace among nations. (1)
Nor is there any difference in this matter [i.e. the "empire of our Redeemer"] 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... 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. (18)
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. (19)
That's 1925. Kind of shocking, isn't it? Somewhere along the forty years between Quas primas and Vatican II, the Church decided to make friends with the project of European modernity, and with it the idea of secular, pluralistic, modern democracy. And so, as we turned from other-worldly salvation to justice and peace, the funny feast of Christ the King had to take the opposite path and be changed from a politically-charged observance to a work of awe and wonder at the world to come. The politics of Christ the King went out of style, but since you can't just get rid of a feast day instituted by a Pope, the best thing you can do is to make it mystical.
But now, another fifty years on since Vatican II, perhaps the concerns of those who made such a fuss about 'modernism' are looking a little less stuffy and reactionary, as the happy friendship between the Church and modern liberal democracy starts to show some signs of stress.
Christus vincit, Christus regnat, Christus imperat