The Church’s magisterium has devoted more attention to marriage in the modern era than in any previous time. This has been a response to the many moral and doctrinal challenges to marriage, but it also connects with the broader project of Catholic social teaching launched by Leo XIII, for marriage is the basis of the fundamental social unit, the family.
Leo began the new era of frequent papal teaching on marriage on February 10, 1880, with the publication of his fourth encyclical, Arcanum. It was, Russell Hittinger notes, “the first formal and synoptic teaching on marriage since the Council of Trent”—a gap of four centuries.
It is worth noting that Leo XIII’s Arcanum and Pius XI’s Casti Connubii, the latter written for the first encyclical’s fiftieth anniversary in 1930, are still the highest-level papal documents that have been devoted specifically to summarizing Church teaching on marriage. The only comparable document since then is John Paul II’s Familiaris Consortio, but it is broader in scope, dealing with the life of the family in society more generally.
Arcanum and Casti are distinct in their focus. Arcanum frames the subject mainly in terms of what the Church has done to uplift and protect marriage throughout history. Leo argues at length that the state has no right to usurp the Church’s governance of marriage.
Casti Connubii, while building on the foundation laid by Leo, is even more expansive about marriage itself, its ends, and how it should be lived, from the point of view of the spouses. In fact, if I were to recommend every Catholic read one Church document on marriage, it would easily be Casti Connubii (you can listen to our free audiobook of it).
I love it because it is both old enough to reiterate aspects of marriage that modern Church