1. The reflections we have thus far made on human love in the divine plan would be in some way incomplete if we did not try to see their concrete application in the sphere of marital and family morality. We want to take this further step that will bring us to the conclusion of our now long journey, under the guidance of an important recent pronouncement of the Magisterium, Humanae Vitae, which Pope Paul VI published in July 1968. We will reread this significant document in the light of the conclusions we have reached in examining the initial divine plan and the words of Christ which refer to it.
2. "The Church teaches as absolutely required that in any use whatever of marriage there must be no impairment of its natural capacity to procreate human life" (Humanae Vitae 11). "This particular doctrine, often expounded by the Magisterium of the Church, is based on the inseparable connection, established by God, which man on his own initiative may not break, between the unitive significance and the procreative significance which are both inherent to the marriage act" (Humane Vitae 12).
3. The considerations I am about to make concern especially the passage of Humanae Vitae that deals with the "two significances of the marriage act" and their "inseparable connection." I do not intend to present a commentary on the whole encyclical, but rather to illustrate and examine one of its passages. From the point of view of the doctrine contained in the quoted document, that passage has a central significance. At the same time, that passage is closely connected with our previous reflections on marriage in its dimension as a (sacramental) sign.
As I said, since this is a central passage of the encyclical, it is obvious that it constitutes a very important part of its whole structure. Therefore, its analysis must direct us toward the various components of that structure, even if it is not our intention to comment on the entire text.
A promised fidelity
4. In the reflections on the sacramental sign, it has already been said several times that it is based on the language of the body reread in truth. It concerns a truth once affirmed at the beginning of the marriage when the newlyweds, promising each other "to be always faithful...and to love and honor each other all the days of their life," become ministers of marriage as a sacrament of the Church.
It concerns, then, a truth that is always newly affirmed. In fact, the man and the woman, living in the marriage "until death," re-propose uninterruptedly, in a certain sense, that sign that they made—through the liturgy of the sacrament—on their wedding day.
The aforementioned words of Pope Paul VI's encyclical concern that moment in the common life of the spouses when both, joining each other in the marriage act, become, according to the biblical expression, "one flesh" (Gn 2:24). Precisely at such a moment so rich in significance, it is also especially important that the language of the body be reread in truth. This reading becomes the indispensable condition for acting in truth, that is, for behaving in accordance with the value and the moral norm.
5. The encyclical not only recalls this norm, but also seeks to give it adequate foundation. In order to clarify more completely that "inseparable connection, established by God...between the unitive significance and the procreative significance of the marriage act," Paul VI writes in the next sentence: "The reason is that the marriage act, because of its fundamental structure, while it unites husband and wife in the closest intimacy, also brings into operation laws written into the actual nature of man and of woman for the generation of new life" (Humanae Vitae 12).
We note that in the previous sentence, the text just quoted deals above all with the significance of marital relations. In the following sentence, it deals with the fundamental structure (that is, the nature) of marital relations. Defining that fundamental structure, the text refers to "laws written into the actual nature of man and of woman."
The passage from the sentence expressing the moral norm, to the sentence which explains and justifies it, is especially significant. The encyclical leads one to seek the foundation for the norm which determines the morality of the acts of the man and the woman in the marriage act, in the nature of this very act, and more deeply still, in the nature of the subjects themselves who are performing the act.
6. In this way, the fundamental structure (that is, the nature) of the marriage act constitutes the necessary basis for an adequate reading and discovery of the two significances that must be carried over into the conscience and the decisions of the acting parties. It also constitutes the necessary basis for establishing the adequate relationship of these significances, that is, their inseparable connection. Since "the marriage act..."—at the same time—"unites husband and wife in the closest intimacy" and together "makes them capable of generating new life," and both the one and the other happen "through the fundamental structure," then it follows that the human person (with the necessity proper to reason, logical necessity) must read at the same time the "twofold significance of the marriage act" and also the "inseparable connection between the unitive significance and the procreative significance of the marriage act."
Here we are dealing with nothing other than reading the language of the body in truth, as has been said many times in our previous biblical analyses. The moral norm, constantly taught by the Church in this sphere, and recalled and reconfirmed by Paul VI in his encyclical, arises from the reading of the language of the body in truth.
It is a question here of the truth first in the ontological dimension ("fundamental structure") and then—as a result—in the subjective and psychological dimension ("significance"). The text of the encyclical stresses that in the case in question we are dealing with a norm of the natural law.