When it is a question of harmonizing married love with the responsible transmission of life, the morality of the behavior does not depend on sincere intention and evaluation of motives alone; but it must be determined by objective criteria, criteria drawn from the nature of the person and his acts, and human procreation in the context of true love; this is possible only if the virtue of married chastity is practiced with sincerity of heart. (CCC, #2368) The work of educating in the service of life involves the training of married couples in responsible procreation. In its true meaning, responsible procreation requires couples to be obedient to the Lord's call and to act as faithful interpreters of his plan. This happens when the family is generously open to new lives, and when couples maintain an attitude of openness and service to life, even if, for serious reasons and in respect for the moral
w, they choose to avoid a new birth for the time being or indefinitely. The moral law obliges them in every case to control the impulse of instinct and passion, and to respect the biological laws inscribed in their person. It is precisely this respect which makes legitimate, at the service of responsible procreation, the use of natural methods of regulating fertility. (EV, #97) Finally, it is for parents to take a thorough look at the matter and decide upon the number of their children. This is an obligation they take upon themselves, before their children already born, and before the community to which they belong—following the dictates of their own consciences informed by God's law authentically interpreted, and bolstered by their trust in Him. (Paul VI, PP, March 26, 1967, #37) The moral lawfulness of such conduct [limiting the use of the marital act to times of natural sterility] would be affirmed or denied according as to whether or not the intention to keep constantly to these periods is based on sufficient and reliable moral grounds. The sole fact that the couple do not offend against the nature of the act and that they are willing to accept and bring up the child that is born notwithstanding the precautions they have taken, would not of itself alone be sufficient guarantee of a right intention and of the unquestionable morality of the motives themselves. (Pius XII, Allocution to Midwives, October 29, 1951) To embrace the married state, to make frequent use of the faculty proper to it and lawful only in that state, while on the other hand, always and deliberately to seek to evade its primary duty without serious reason, would be to sin against the very meaning of married life. (Pius XII, Allocution to Midwives, October 29, 1951) Serious reasons, often put forward on medical, eugenic, economic and social grounds, can exempt from that obligatory service even for a considerable period of time, even for the entire duration of the marriage. It follows from this that the use of the infertile periods can be lawful from the moral point of view and, in the circumstances which have been mentioned, it is indeed lawful. If, however, in the light of a reasonable and fair judgment, there are no such serious personal reasons, or reasons deriving from external circumstances, then the habitual intention to avoid the fruitfulness of the union, while at the same time continuing fully to satisfy sensual intent, can only arise from a false appreciation of life and from motives that run counter to true standards of moral conduct. (Pius XII, Allocution to Midwives, October 29, 1951) Responsible fatherhood and motherhood include not only the couple's prudent decisions but also the refusal of artificial methods of birth control and, when there are serious reasons, the choice of the natural regulation of fertility. (PCF, The Ethical and Pastoral Dimensions of Population Trends, March 25, 1994, #46) A truly responsible fatherhood and motherhood begin with the couple’s responsibility before the author and Lord of life. Such fatherhood and motherhood are based upon generosity within marriage and the respect of the unborn child’s right to life. (PCF, The
ethical and Pastoral Dimensions of Population Trends, March 25, 1994, #73) Through their own experience spouses come to learn the meaning of responsible fatherhood and motherhood. They learn it also from the experience of other couples in similar situations and as they become more open to the findings of the various sciences. One could say that "experts" learn in a certain sense from "spouses", so that they in turn will then be in a better position to teach married couples the meaning of responsible procreation and the ways to achieve it. (John Paul II, Gratissimam sane, February 2, 1994, #12) They then experience a moment of special responsibility, which is also the result of the procreative potential linked to the conjugal act. At that moment, the spouses can become father and mother, initiating the process of a new human life, which will then develop in the woman's womb. If the wife is the first to realize that she has become a mother, the husband, to whom she has been united in "one flesh", then learns this when she tells him that he has become a father. Both are responsible for their potential and later actual fatherhood and motherhood. (John Paul II, Gratissimam sane, February 2, 1994, #12