1. The Encyclical "Humanae vitae," while demonstrating the moral evil of contraception, at the same time fully approves of the natural regulation of fertility and, in this sense, it approves of responsible parenthood. Here one must exclude the possibility of describing as "responsible" from the ethical point of view that procreation in which recourse is had to contraception in order to regulate fertility. The true concept of "responsible parenthood" is, on the contrary, connected with the right and lawful regulation of fertility from the ethical viewpoint.
2. We read in this regard: "The right and lawful ordering of the births of children presupposes in husband and wife first and foremost that they fully recognize and value the true blessings of family life, and secondly, that they acquire complete mastery over themselves and their emotions. For if with the aid of reason and of free will they are to control their natural drives, there can be no doubt at all of the need for self-denial. Only then will the expression of love, particular to the married life, conform to right order. And this is especially true as regards the practice of periodic continence. But self-discipline of this kind is a shining witness to the chastity of husband and wife and, so far from being a hindrance to their love of one another, transforms it by giving it a more truly human character. And if this self-discipline does demand that they persevere in their purpose and efforts, it has at the same time the salutary effect of enabling husband and wife to develop to the full their personalities and be enriched with spiritual blessings..." (HV 21).
3. The encyclical then points out the consequences of such a line of conduct not merely for the couple themselves but also for the whole family understood as a community of persons. It will be necessary to treat again of this subject. The encyclical underlines that a right and lawful regulation of fertility demands above all from husband and wife a definite family and procreative attitude: that is to say, it requires "that they acquire and possess solid convictions about the true values of life and of the family" (HV 21). Beginning from this premise, it was necessary to proceed to an overall consideration of the of the question as was done by the Synod of Bishops in 1980 ("On the Role of the Christian Family"). Later, the doctrine concerning this particular problem of conjugal and family morality, treated in the Encyclical "Humanae vitae", found its proper place and fitting perspective in the comprehensive context of the Apostolic Exhortation "Familiaris consortio". The theology of the body, particularly as the pedagogy of the body, has its roots, in a certain sense, in the theology of the family and, at the same time, leads to it. This pedagogy of the body, whose key today is the Encyclical "Humanae vitae", is explained only in the full context of a correct vision of the values of life and of the family.
4. In the text quoted above Pope Paul VI refers to conjugal chastity when he writes that the observance of periodic continence is the form of self-mastery in which "conjugal chastity" is manifested (HV 21).
In undertaking now a deeper analysis of this problem it is necessary to bear in mind the whole doctrine on chastity understood as the life of the Spirit (cf. Gal. 5:25), already considered by us previously, in order to understand the respective statements of the encyclical on the theme of "periodic continence." That doctrine remains indeed the real reason, beginning from which the teaching of Paul VI defines the regulation of births and responsible parenthood as ethically right and lawful.
Even though the "periodicity" of continence is in this case applied to the so-called "natural rhythms" (HV 16), however, the continence itself is a definite and permanent moral attitude; it is a virtue, and therefore, the whole line of conduct guided by it acquires a virtuous character. The encyclical emphasizes clearly enough that here it is not merely a matter of a definite "technique," but of ethics in the strict sense of the term as the morality of conduct.
Therefore, the encyclical opportunely sets out in relief, on the one hand, the necessity to respect in the above-mentioned line of conduct the order established by the Creator, and on the other hand, the necessity of an immediate motivation of an ethical character.
5. In regard to the first aspect we read: "To experience the gift of married love while respecting the laws of conception is to acknowledge that one is not the master of the sources of life, but rather the minister of the design established by the Creator" (HV 13). "Human life is sacred"--as our Predecessor of holy memory, John XXIII, said in his Encyclical "Mater et magistra"--"from its very beginning it involves directly the creative action of God" (AAS 53, 1961; cf. HV 13). As regards the immediate motivation, the Encyclical "Humanae vitae" requires that "there exist reasonable grounds for spacing births, arising from the physical or psychological condition of husband or wife, or from external circumstances..." (HV 16).
6. In the case of a morally upright regulation of fertility effected by means of periodic continence, one is clearly dealing with the practice of conjugal chastity, that is, of a definite ethical attitude. In biblical language we could say that it is a case of living by the Spirit (cf. Gal. 5:25).
The morally correct regulation is also called "the natural regulation of fertility," which can be explained as conformity to the "natural law." By "natural law" we mean that "order of nature" in the field of procreation, insofar as it is understood by right reason: this order is the expression of the Creator's plan for man. And it is precisely this that the encyclical, together with the whole Tradition of Christian teaching and practice, stresses in a particular way: the virtuous character of the attitude which is expressed in the "natural" regulation of fertility is determined not so much by fidelity to an impersonal "natural law" as to the Creator-Person, the Source and Lord of the order which is manifested in such a law.
From this point of view, the reduction to a mere biological regularity, separated from the "order of nature" that is, from the "Creator's plan," deforms the authentic thought of the Encyclical "Humanae vitae" (cf. HV 14).
The document certainly presupposes that biological regularity-- indeed, it exhorts competent persons to study it and to apply it in a still deeper way--but it always understands this regularity as the expression of the "order of nature," that is, of the providential plan of the Creator, in the faithful execution of which the true good of the human person consists.