11. These acts, by which husband and wife are united in chaste intimacy, and by means of which human life is transmitted, are, as the Council recalled, "noble and worthy," [Ibid, no. 49.] and they do not cease to be lawful if, for causes independent of the will of husband and wife, they are foreseen to be infecund, since they always remain ordained towards expressing and consolidating their union. In fact, as experience bears witness, not every conjugal act is followed by a new life. God has wisely disposed natural laws and rhythms of fecundity which, of themselves, cause a separation in the succession of births. Nonetheless the Church, calling men back to the observance of the norms of the natural law, as interpreted by their constant doctrine, teaches that each and every marriage act (quilibet matrimonii usus) must remain open to the transmission of life. [Cf. Pius XI, encyc. Casti Connubii, in AAS XXII (1930), p. 560; Pius XII, in AAS XLIII (1951), p. 843.]
12. 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. Indeed, 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. By safeguarding both these essential aspects, the unitive and the procreative, the conjugal act preserves in its fullness the sense of true mutual love and its ordination towards man's most high calling to parenthood. We believe that the men of our day are particularly capable of seeing the deeply reasonable and human character of this fundamental principle.
14. In conformity with these landmarks in the human and Christian vision of marriage, we must once again declare that the direct interruption of the generative process already begun, and, above all, directly willed and procured abortion, even if for therapeutic reasons, are to be absolutely excluded as licit means of regulating birth. [Cf. Catechismus Romanus Concilii Tridentini, part. II, Ch. VIII; Pius XI, encyc. Casti Connubii, in AAS XXII (1930), pp. 562-564; Pius XII, Discorsi e Radiomessaggi, VI (1944), pp. 191-192; AAS XLIII (1951), pp. 842-843; pp. 857-859; John XXIII, encyc. Pacem in Terris, Apr. 11, 1963, in AAS LV (1963), pp. 259-260; Gaudium et Spes, no. 51.]
Equally to be excluded, as the teaching authority of the Church has frequently declared, is direct sterilization, whether perpetual or temporary, whether of the man or of the woman. [Cf. Pius XI encyc. Casti Connubii, in AAS XXII (1930) p. 565; decree of the Holy Office, Feb. 22, 1940, in AAS L (1958), pp. 734-735.] Similarly excluded is every action which, either in anticipation of the conjugal act, or in its accomplishment, or in the development of its natural consequences, proposes, whether as an end or as a means, to render procreation impossible. [Cf. Catechismus Romanus Concilii Tridentini, part. II, Ch. VIII; Pius XI, encyc. Casti Connubii, in AAS XXII (1930), pp. 559-561; Pius XII, AAS XLIII (1951), p. 843; AAS L. (1958), pp. 734-735; John XXIII, encyc. Mater et Magistra, in AAS LIII (1961), p. 447.]
To justify conjugal acts made intentionally infecund, one cannot invoke as valid reasons the lesser evil, or the fact that such acts would constitute a whole together with the fecund acts already performed or to follow later, and hence would share in one and the same moral goodness. In truth, if it is sometimes licit to tolerate a lesser evil in order to avoid a greater evil or to promote a greater good, [Cf. Pius XII, alloc. to the National Congress of the Union of Catholic Jurists, Dec. 6, 1953, in AAS XLV (1953), pp. 798-799.] it is not licit, even for the gravest reasons, to do evil so that good may follow therefrom; [Cf. Rom. 3: 8.] that is, to make into the object of a positive act of the will something which is intrinsically disorder, and hence unworthy of the human person, even when the intention is to safeguard or promote individual, family or social well-being. Consequently it is an error to think that a conjugal act which is deliberately made infecund and so is intrinsically dishonest could be made honest and right by the ensemble of a fecund conjugal life.
16. To this teaching of the Church on conjugal morals, the objection is made today, as we observed earlier (# 3), that it is the prerogative of the human intellect to dominate the energies offered by irrational nature and to orientate them towards an end conformable to the good of man. Now, some may ask: in the present case, is it not reasonable in many circumstances to have recourse to artificial birth control if, thereby, we secure the harmony and peace of the family, and better conditions for the education of the children already born? To this question it is necessary to reply with clarity: the Church is the first to praise and recommend the intervention of intelligence in a function which so closely associates the rational creature with his Creator; but she affirms that this must be done with respect for the order established by God.
If, then, there are serious motives to space out births, which derive from the physical or psychological conditions of husband and wife, or from external conditions, the Church teaches that it is then licit to take into account the natural rhythms immanent in the generative functions, for the use of marriage in the infecund periods only, and in this way to regulate birth without offending the moral principles which have been recalled earlier. [Cf. Pius XII, AAS XLIII (1951), p. 846.]
The Church is coherent with herself when she considers recourse to the infecund periods to be licit, while at the same time condemning, as being always illicit, the use of means directly contrary to fecundation, even if such use is inspired by reasons which may appear honest and serious. In reality, there are essential differences between the two cases; in the former, the married couple make legitimate use of a natural disposition; in the latter, they impede the development of natural processes. It is true that, in the one and the other case, the married couple are concordant in the positive will of avoiding children for plausible reasons, seeking the certainty that offspring will not arrive; but it is also true that only in the former case are they able to renounce the use of marriage in the fecund periods when, for just motives, procreation is not desirable, while making use of it during infecund periods to manifest their affection and to safeguard their mutual fidelity. By so doing, they give proof of a truly and integrally honest love.
23. To Rulers, who are those principally responsible for the common good, and who can do so much to safeguard moral customs, we say: Do not allow the morality of your peoples to be degraded; do not permit that by legal means practices contrary to the natural and divine law be introduced into that fundamental cell, the family. Quite other is the way in which public authorities can and must contribute to the solution of the demographic problem: namely, the way of a provident policy for the family, of a wise education of peoples in respect of moral law and the liberty of citizens.
We are well aware of the serious difficulties experienced by public authorities in this regard, especially in the developing countries. To their legitimate preoccupations we devoted our encyclical letter Populorum Progressio. But with our predecessor Pope John XXIII, we repeat: no solution to these difficulties is acceptable "which does violence to man's essential dignity" and is based only on an utterly materialistic conception of man himself and of his life. The only possible solution to this question is one which envisages the social and economic progress both of individuals and of the whole of human society, and which respects and promotes true human values. [Cf. encyc. Mater et Magistra in AAS LIII (1961), p. 447.] Neither can one, without grave injustice, consider divine providence to be responsible for what depends, instead, on a lack of wisdom in government, on an insufficient sense of social justice, on selfish monopolization, or again on blameworthy indolence in confronting the efforts and the sacrifices necessary to ensure the raising of living standards of a people and of all its sons. [Cf. encyc. Populorum Progressio, nos. 48-55.]
May all responsible public authorities - as some are already doing so laudably - generously revive their efforts. And may mutual aid between all the members of the great human family never cease to grow: This is an almost limitless field which thus opens up to the activity of the great international organizations.