The entirety of this encyclical can be found here, and if I were able to paste it here and still remain somewhat concise and on-task, I would. Please note the date of issuance and the relevance of it even now (relevance being the buzz-word for many current theological 'dialogues').
From Humanae Vitae (Of Human Life), issued 25 July 1968 by His Holiness Pope Paul VI [emphasis mine]:
'. . .[17]Responsible men can become more deeply convinced of the truth of the doctrine laid down by the Church . . . 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.
'. . .[18] 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 of communication. But it comes 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.
'. . .[23] And now We wish to speak to rulers of nations. To you most of all is committed the responsibility of safeguarding the common 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. . . .'
-r
