Fifty years ago this week, Pope Paul VI released Humanae Vitae, an encyclical on marital love, responsible parenthood, and artificial contraception. Because contraception profoundly influences so many areas of life—from the family to national policies—this statement on human anthropology and sexuality has e a one of the most significant documents of Catholic social thought.

In honor of the anniversary, here are 30 key quotes from the papal encyclical:

The transmission of human life is a most serious role in which married people collaborate freely and responsibly with God the Creator. It has always been a source of great joy to them, even though it sometimes entails many difficulties and hardships. The fulfillment of this duty has always posed problems to the conscience of married people, but the recent course of human society and the itant changes have provoked new questions. The Church cannot ignore these questions, for they concern matters intimately connected with the life and happiness of human beings.

Problem and Competency of the Magisterium

The changes that have taken place are of considerable importance and varied in nature. In the first place there is the rapid increase in population which has made many fear that world population is going to grow faster than available resources, with the consequence that many families and developing countries would be faced with greater hardships. This can easily induce public authorities to be tempted to take even harsher measures to avert this danger. There is also the fact that not only working and housing conditions but the greater demands made both in the economic and educational field pose a living situation in which it is frequently difficult these days to provide properly for a large family.

Doctrinal Principles

The question of human procreation, like every other question which touches human life, involves more than the limited aspects specific to such disciplines as biology, psychology, demography or sociology. It is the whole man and the whole mission to which he is called that must be considered: both its natural, earthly aspects and its supernatural, eternal aspects. And since in the attempt to justify artificial methods of birth control many appeal to the demands of married love or of responsible parenthood, these two important realities of married life must be accurately defined and analyzed.

God’s Loving Design

Married love particularly reveals its true nature and nobility when we realize that it takes its origin from God, who “is love,” the Father “from whom every family in heaven and on earth is named.”

Marriage, then, is far from being the effect of chance or the result of the blind evolution of natural forces. It is in reality the wise and provident institution of God the Creator, whose purpose was to effect in man His loving design. As a consequence, husband and wife, through that mutual gift of themselves, which is specific and exclusive to them alone, develop that union of two persons in which they perfect one another, cooperating with God in the generation and rearing of new lives.

Married Love

…[T]his love is fecund. It is not confined wholly to the loving interchange of husband and wife; it also contrives to go beyond this to bring new life into being. “Marriage and conjugal love are by their nature ordained toward the procreation and education of children. Children are really the supreme gift of marriage and contribute in the highest degree to their parents’ welfare.”

Responsible Parenthood

With regard to the biological processes, responsible parenthood means an awareness of, and respect for, their proper functions. In the procreative faculty the human mind discerns biological laws that apply to the human person. With regard to man’s innate drives and emotions, responsible parenthood means that man’s reason and will must exert control over them. With regard to physical, economic, psychological and social conditions, responsible parenthood is exercised by those who prudently and generously decide to have more children, and by those who, for serious reasons and with due respect to moral precepts, decide not to have additional children for either a certain or an indefinite period of time.

Responsible parenthood, as we use the term here, has one further essential aspect of paramount importance. It concerns the objective moral order which was established by God, and of which a right conscience is the true interpreter. In a word, the exercise of responsible parenthood requires that husband and wife, keeping a right order of priorities, recognize their own duties toward God, themselves, their families and human society.

Observing the Natural Law

The sexual activity, in which husband and wife are intimately and chastely united with one another, through which human life is transmitted, is, as the recent Council recalled, “noble and worthy.” It does not, moreover, cease to be legitimate even when, for reasons independent of their will, it is foreseen to be infertile. For its natural adaptation to the expression and strengthening of the union of husband and wife is not thereby suppressed.

The Church, nevertheless, in urging men to the observance of the precepts of the natural law, which it interprets by its constant doctrine, teaches that each and every marital act must of necessity retain its intrinsic relationship to the procreation of human life.

Union and Procreation

…[T]he fundamental nature of the marriage act, while uniting husband and wife in the closest intimacy, also renders them capable of generating new life—and this as a result of laws written into the actual nature of man and of woman. And if each of these essential qualities, the unitive and the procreative, is preserved, the use of marriage fully retains its sense of true mutual love and its ordination to the supreme responsibility of parenthood to which man is called.

Faithfulness to God’s Design

Men rightly observe that a conjugal act imposed on one’s partner without regard to his or her condition or personal and reasonable wishes in the matter, is no true act of love, and therefore offends the moral order in its particular application to the intimate relationship of husband and wife.

Just as man does not have unlimited dominion over his body in general, so also, and with more particular reason, he has no such dominion over his specifically sexual faculties, for these are concerned by their very nature with the generation of life, of which God is the source.

Unlawful Birth Control Methods

Therefore We base Our words on the first principles of a human and Christian doctrine of marriage when We are obliged once more to declare that the direct interruption of the generative process already begun and, above all, all direct abortion, even for therapeutic reasons, are to be absolutely excluded as lawful means of regulating the number of children. Equally to be condemned, as the magisterium of the Church has affirmed on many occasions, is direct sterilization, whether of the man or of the woman, whether permanent or temporary.

Similarly excluded is any action which either before, at the moment of, or after sexual intercourse, is specifically intended to prevent procreation—whether as an end or as a means.

Recourse to Infertile Periods

If therefore there are well-grounded reasons for spacing births, arising from the physical or psychological condition of husband or wife, or from external circumstances, the Church teaches that married people may then take advantage of the natural cycles immanent in the reproductive system and engage in marital intercourse only during those times that are infertile, thus controlling birth in a way which does not in the least offend the moral principles which We have just explained.

Consequences of Artificial Methods

Responsible men can e more deeply convinced of the truth of the doctrine laid down by the Church on this issue if they reflect on the consequences of methods and plans for artificial birth control. Let them first consider how easily this course of action could open wide the way for marital infidelity and a general lowering of moral standards. Not much experience is needed to be fully aware of human weakness and to understand that human beings—and especially the young, who are so exposed to temptation—need incentives to keep the moral law, and it is an evil thing to make it easy for them to break that law. Another effect that gives cause for alarm is that a man who grows accustomed to the use of contraceptive methods may forget the reverence due to a woman, and, disregarding her physical and emotional equilibrium, reduce her to being a mere instrument for the satisfaction of his own desires, no longer considering her as his partner whom he should surround with care and affection.

Finally, careful consideration should be given to the danger of this power passing into the hands of those public authorities who care little for the precepts of the moral law. Who will blame a government which in its attempt to resolve the problems affecting an entire country resorts to the same measures as are regarded as lawful by married people in the solution of a particular family difficulty? Who will prevent public authorities from favoring those contraceptive methods which they consider more effective? Should they regard this as necessary, they may even impose their use on everyone. It could well happen, therefore, that when people, either individually or in family or social life, experience the inherent difficulties of the divine law and are determined to avoid them, they may give into the hands of public authorities the power to intervene in the most personal and intimate responsibility of husband and wife.

Limits to Man’s Power

Consequently, unless we are willing that the responsibility of procreating life should be left to the arbitrary decision of men, we must accept that there are certain limits, beyond which it is wrong to go, to the power of man over his own body and its natural functions—limits, let it be said, which no one, whether as a private individual or as a public authority, can lawfully exceed.

Concern of the Church

It is to be anticipated that perhaps not everyone will easily accept this particular teaching. There is too much clamorous outcry against the voice of the Church, and this is intensified by modern means munication. But es as no surprise to the Church that she, no less than her divine Founder, is destined to be a “sign of contradiction.” She does not, because of this, evade the duty imposed on her of proclaiming humbly but firmly the entire moral law, both natural and evangelical.

Since the Church did not make either of these laws, she cannot be their arbiter—only their guardian and interpreter. It could never be right for her to declare lawful what is in fact unlawful, since that, by its very nature, is always opposed to the true good of man.

In preserving intact the whole moral law of marriage, the Church is convinced that she is contributing to the creation of a truly human civilization. She urges man not to betray his personal responsibilities by putting all his faith in technical expedients.

Value of Self-Discipline

The right and lawful ordering of birth demands, first of all, that spouses fully recognize and value the true blessings of family life and that they plete 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, essential to married life, conform to right order.

Promotion of Chastity

We take this opportunity to address those who are engaged in education and all those whose right and duty it is to provide for mon good of human society. We would call their attention to the need to create an atmosphere favorable to the growth of chastity so that true liberty may prevail over license and the norms of the moral law may be fully safeguarded.

Everything therefore in the modern means of munication which arouses men’s baser passions and encourages low moral standards, as well as every obscenity in the written word and every form of indecency on the stage and screen, should be condemned publicly and unanimously by all those who have at heart the advance of civilization and the safeguarding of the outstanding values of the human spirit. It is quite absurd to defend this kind of depravity in the name of art or culture or by pleading the liberty which may be allowed in this field by the public authorities.

Appeal to Public Authorities

And now We wish to speak to rulers of nations. To you most of all mitted the responsibility of safeguarding mon good. You can contribute so much to the preservation of morals. We beg of you, never allow the morals of your peoples to be undermined. The family is the primary unit in the state; do not tolerate any legislation which would introduce into the family those practices which are opposed to the natural law of God. For there are other ways by which a government can and should solve the population problem—that is to say by enacting laws which will assist families and by educating the people wisely so that the moral law and the freedom of the citizens are both safeguarded.

Seeking True Solutions

We are fully aware of the difficulties confronting the public authorities in this matter, especially in the developing countries. . . . No one can, without being grossly unfair, make divine Providence responsible for what clearly seems to be the result of misguided governmental policies, of an insufficient sense of social justice, of a selfish accumulation of material goods, and finally of a culpable failure to undertake those initiatives and responsibilities which would raise the standard of living of peoples and their children. If only all governments which were able would do what some are already doing so nobly, and bestir themselves to renew their efforts and their undertakings! There must be no relaxation in the programs of mutual aid between all the branches of the great human family. Here We believe an almost limitless field lies open for the activities of the great international institutions.

To Christian Couples

[L]et Christian husbands and wives be mindful of their vocation to the Christian life, a vocation which, deriving from their Baptism, has been confirmed anew and made more explicit by the Sacrament of Matrimony. For by this sacrament they are strengthened and, one might almost say, consecrated to the faithful fulfillment of their duties. Thus will they realize to the full their calling and bear witness as es them, to Christ before the world. For the Lord has entrusted to them the task of making visible to men and women the holiness and joy of the law which united inseparably their love for one another and the cooperation they give to God’s love, God who is the Author of human life.

To Doctors and Nurses

Likewise we hold in the highest esteem those doctors and members of the nursing profession who, in the exercise of their calling, endeavor to fulfill the demands of their Christian vocation before any merely human interest. Let them therefore continue constant in their resolution always to support those lines of action which accord with faith and with right reason. And let them strive to win agreement and support for these policies among their professional colleagues.

A Great Work

Venerable brothers, beloved sons, all men of good will, great indeed is the work of education, of progress and of charity to which We now summon all of you. And this We do relying on the unshakable teaching of the Church, which teaching Peter’s successor together with his brothers in the Catholic episcopate faithfully guards and interprets. And We are convinced that this truly great work will bring blessings both on the world and on the Church. For man cannot attain that true happiness for which he yearns with all the strength of his spirit, unless he keeps the laws which the Most High God has engraved in his very nature. These laws must be wisely and lovingly observed. On this great work, on all of you and especially on married couples, We implore from the God of all holiness and pity an abundance of heavenly grace as a pledge of which We gladly bestow Our apostolic blessing.