JP II comments on Pope Paul VI’s encyclical Humanae Vitae and the nature of the marital act:
“The Church…teaches that each and every marriage act must remain through itself open to the transmission of life. That teaching, often set forth by the magisterium, is founded upon the inseparable connection, willed by god and unable to be broken by man on his own initiative, between the two meanings of the conjugal act: the unitive meaning and the procreative meaning (HV, 11-12)…
…In order to clarify more deeply that “inseparable connection, willed by God…between the two meanings of the conjugal act,” Paul VI writes…as follows: “By its intimate structure, the conjugal act, while most closely uniting husband and wife, capacitates them for the generation of new lives, according to laws inscribed in the very being of man and of woman (HV, 12).
We observe that in the preceding sentence the text just quoted deals above all with “meaning” and in the sentence after this with the “innermost structure” (that is, nature) of conjugal relations. When it defines this “innermost structure,” the text refers to “laws inscribed in the very being of man and woman.”
…Nothing else is at stake here than reading the “language of the body” in the truth, as has been said several times in the earlier biblical analysis. The moral norm, constantly taught by the Church in this sphere, recalled and reconfirmed by Paul VI in his encyclical, springs from reading the “language of the body” in the truth.
What is at stake here is the truth, first in the ontological dimension (“innermost structure”) and then – as a consequence – in the subjective and psychological dimension (“meaning”) The text of the encyclical underlines that in this case we are dealing with a norm of the natural law.
–General Audience of July 11, 1984, TOB 118:2, 5, 6)
The people who say that “sex is natural” really are onto something. However, when they use that as their basis for their belief that, therefore everybody should be allowed to “just do it” whenever and with whomever they feel like, they essentially ignore, or totally deny, the act’s most basic and “natural” functions? Of course sex is, and should be, a pleasurable experience, but it is not an end in and of itself. It was created as a means of uniting one man and one woman and (God willing) building a family through that union.
This is what our bodies tell us! If only we would listen.