It is very important to remember the writer's intended audience when examining this document. Pope Pius XI, when he wrote this papal encyclical in December of 1930, was not addressing the general public or even the laity, the ordinary members of the Catholic church. He was addressing clerics only—and higher-up ones at that—such as the archbishops, the bishops, and so on, on matters of doctrinal law. A papal encyclical is a kind of official document in which the pope addresses some element of church doctrine in a letter to these officials. This particular encyclical was prompted by a recent change in the Anglican Church. At their Lambeth conference, held once every ten years, the Anglicans had decided to relax their stance on the use of birth control in certain situations. In Casti Connubii, Pius reaffirms that the Catholic church's stance on birth control remains unchanged and also explains why.

Pius appears to feel as though there are multiple attacks on morality against which the church must defend. For example, he addresses the fact that divorce is legal and has become more prevalent in modern society. However, even though it is not against the law, it is not recognized by the church. For the church, once someone is married, they are married until one partner's death. Even if they procure a legal divorce, they will be considered an adulterer in the eyes of the Catholic Church if they remarry while their first spouse remains living. Pius also takes issue with popular culture texts, like movies and books, that make marriage seem unfulfilling or restrictive; if divorce were not presented as such an easy and viable escape, then people would be less likely to pursue it. Birth control is also legal, but because it disrupts the purpose for which God sanctified marriage—to produce children—it is also sinful. Pius discusses recent strides that have been made in terms of women's liberation, and he paints certain progressive ideas concerning women's sexual independence as misguided and dangerous. Pius speaks as one who feels that what the Catholic church represents is under attack, and Casti Connubii represents his efforts to shore up traditional doctrine in a changing world.