This kind of question requires from the teaching authority of the Church a new and deeper reflection on the principles of the moral teaching on marriage—a teaching which is based on the natural law as illuminated and enriched by divine Revelation.
I think this is interesting: first we have to establish the teaching authority of the Church as the interpreter of the natural law. Secondly, the teaching of this encyclical BEGINS with natural law as illumined by Revelation, not the other way around.
No member of the faithful could possibly deny that the Church is competent in her magisterium to interpret the natural moral law. It is in fact indisputable, as Our predecessors have many times declared, (l) that Jesus Christ, when He communicated His divine power to Peter and the other Apostles and sent them to teach all nations His commandments, (2) constituted them as the authentic guardians and interpreters of the whole moral law, not only, that is, of the law of the Gospel but also of the natural law. For the natural law, too, declares the will of God, and its faithful observance is necessary for men's eternal salvation. (3)
Again the authority of the papacy as inheritors of the apostolate and thus the true interpreters of the moral law is asserted. This is a strategy to protect from arbitrariness. 'Necessary for men's eternal salvation'? Hmm...
With regard to man's innate drives and emotions, responsible parenthood means that man's reason and will must exert control over them.
A curious feature of Thomistic thought: the emphasis on 'reason' in anthropology, over and against the other drives and emotions. Maybe not so curious: it was interesting to see Kant saying exactly the same thing.
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
Here 'right conscience' comes in. Interestingly Cardinal Pell of Sydney has talked about this 'conscience' idea in order to defend it from rampant individualism. He says conscience must be taught rightly and is not a somehow inward part of the human sealed off from church teaching. I think this reveals the problem with the conscience thing, though I am sympathetic to Pell's reasons.The fact is, as experience shows, that new life is not the result of each and every act of sexual intercourse. God has wisely ordered laws of nature and the incidence of fertility in such a way that successive births are already naturally spaced through the inherent operation of these laws. 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.
Strangely Paul doesn't give us much about this 'intrinsic relationship' idea. It is unexplained really... is it to do with the intention to procreate? Well, no, because he will allow for natural birth control later on. You could complain to, that the 'wisely ordered laws of nature' is a problematic teaching: women die in childbirth; successive births aren't 'spaced', etc. That is, the curse has had an effect on the natural world, and it is now not as 'natural' as it once was.
...the 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.
I take it he means our bodily nature and desires for one another have the nature of laws. How do they become 'laws' from being our actual nature?
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.
This is the get-out clause and I have never understood it. To me, this is like a vegetarian eating meat substitute. The rhythm method is still a matter of birth 'control', is it not?
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.
Well, fair enough. The whole population control thing has a very sinister side to it.