40th Anniversary of Humanae Vitae

On July 25th of this year we will commemorate the fortieth anniversary of one of the most important documents of the 20th century, Paul VI's Humane Vitae, On [the transmission of]Human Life.
Many people date the crisis that has undeniably affected the Faith, and the practice of it from the encyclical's promulgation.
I think, rather, we might date the crisis from the observance by the Faithful of disobedient, callous, unfilial and even heretical greeting the document received from, (and from the publicity given to the the manner of greeting by,) those they trusted to know better, from whom they had a right to expect orthodoxy, but by whom they did not see it displayed.
A good time to re-read it....

ENCYCLICAL LETTER
HUMANAE VITAE
OF THE SUPREME PONTIFF PAUL VI
TO HIS VENERABLE BROTHERS THE PATRIARCHS, ARCHBISHOPS, BISHOPS
AND OTHER LOCAL ORDINARIES IN PEACE AND COMMUNION WITH THE APOSTOLIC SEE,
TO THE CLERGY AND FAITHFUL OF THE WHOLE CATHOLIC WORLD,
AND TO ALL MEN OF GOOD WILL,
ON THE REGULATION OF BIRTH
Honored Brothers and Dear Sons, (hmmm... "and daughters" would have been nice. But we must take into account Pope Montini's day)
Health and Apostolic Benediction.
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,
(an refreshingly honest observation) but the recent course of human society and the concomitant 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.
I.
PROBLEM AND COMPETENCY OF THE MAGISTERIUM
2. 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.
Also noteworthy is a new understanding of the dignity of woman and her place in society, (certainly welcome, after his seeming failure to recognize this in his greeting) of the value of conjugal love in marriage and the relationship of conjugal acts to this love.
But the most remarkable development of all is to be seen in man's stupendous progress in the domination and rational organization of the forces of nature to the point that he is endeavoring to extend this control over every aspect of his own life—over his body, over his mind and emotions, over his social life, and even over the laws that regulate the transmission of life.
New Questions
3. This new state of things gives rise to new questions. Granted the conditions of life today and taking into account the relevance of married love to the harmony and mutual fidelity of husband and wife, would it not be right to review the moral norms in force till now, especially when it is felt that these can be observed only with the gravest difficulty, sometimes only by heroic effort?
Moreover, if one were to apply here the so called principle of totality, could it not be accepted that the intention to have a less prolific but more rationally planned family might transform an action which renders natural processes infertile into a licit and provident control of birth? Could it not be admitted, in other words, that procreative finality applies to the totality of married life rather than to each single act? A further question is whether, because people are more conscious today of their responsibilities, the time has not come when the transmission of life should be regulated by their intelligence and will rather than through the specific rhythms of their own bodies.

I think His Holiness spells out the situation, and the aspects of the matter that need addressing nicely, succinctly.