This is the whole point. NFP or the Rhythym method etc... are not sinful when using it to procreate. What makes NFP and ALL birth regulation or control sinful, is when it is used to deliberately frustrate the purpose of the conjugal act, which is the begetting of children. It's pretty clear and not hard to understand. Frustrating the natural power of the act, purposely, is intrinsically vicious to nature as Pope Pius XI says above.

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Except that sterile sex frustrates nothing, even if it is abusive (i.e., "Novus Ordo NFP."). 

I rather think CC supports what I'm saying, rather than what you're saying. Pius XII read it, even cites it in his letter to the midwives (in which he teaches that it is lawful for couples to reserve the marital act to sterile periods for a grave reason). Surely you don't think you understand it better?

 I am a Billings Method Teacher of 1980's.  I do not teach the way the curriculum is set up: Secular with no God, or of the attitude that a young couple can put off having children till their college is finished or such. (couple to couple league brags in their newsletters)  I can say that it was a disappointment to see the beauty of God in the anatomy and physiology to fit the ways of "man's idea".

Sin happens when the Knowledge given to man by God is man's way and not God's.  That is the attitude/heart which will be judged. 

In 1980, I had for the first time a video of Billings and the first book.  I was age 27, young enough not see all.  I had classes with the Billings, twice.  I saw nothing wrong with the curriculum, but it was there, no God was mentioned and it was done very cleverly.  Who did that, I do not know.  It took me time, years to see that.  In 1990, I was offered to please  file for grant money and then I knew there was trouble, because I knew what grants were.  I was offered to read grants by the governor of AZ.  He wanted to know who was bringing sex ed. into the state when it was against the laws.

While that was brewing, I ran into a group: Sympto-thermal.  Well, they did not like Billings, in fact the head person teaching under the dioceses told me there was a blood bath with them.  I also got a bad "attitude" with this head person of ST.  "We teach better than you!"   Better how?  Oh, we do all of these checks of the anatomy.  Well, to make a long story short I happened to run into one of these users and this woman said to me, "How can you go mucus only?"  I said, because that is what God gave us and that is all that is needed.  Thermometer is of man and when you lean too much on so many signs, it can cause aggravation.  Besides, you were taught that thermometer give signs in pre menopause.

So, with those issues circulating in my head and soul, what resulted.  First of all the Billings were very hurt and disappointed when they found the knowledge of Billings go with the taking of federal grants $$$.  Dr. Billings said in front of many people at one of my conferences, "This (Billings knowledge to be taught) is God's!"   
I knew what he was getting across.  He was very unhappy.

Then I found Planned Parenthood teaching Billings by all messed up.  They taught Hi-tech Rhythm, their words.  They said, " Most couples do not wait so use condoms and such.  See!  And what would be PP's results.  I know, pregnancy and PP had high hopes that their way of teaching would result with abortions and also what God gave would be back to what it was in the minds of man, just another rhythm to disregard.

And who brought sex ed. into the state of AZ.  The dioceses.  Wow!  Did I get a wake up call!  Boy, did I need to pray about the whole issue. And I still do. Then I came across how Communism works when reading grants known as KAB.  KAB is used to change the thinking of men.  KAB =Knowledge, attitude, behavior.  Then I read that in our catholicism we do the same and it equals up to sin or to God Glory.  With knowledge we know love and serve God in this world for us to meet in Heaven.  So, behavior would be for me to save my soul.

For communism, to change knowledge OR take truth and twist it, to change attitude, to change behavior.  This is Artificial man made birth control for just a starter.  You can  take KAB and see how it fits communistic ways.

So, after much prayer and I still pray about this, IMO, what God has made is most beautiful.  Depending how it goes to attitude and behaviors is where sin is.  We know God will judge the heart/soul.

IMO there will be serious reasons.  But it is heavily on attitude that needs to be checked!  

Well you say grave reasons legitimatize the act of relegating the conjugal act to periods in which there is virtually no possible way to conceive and refraining from the conjugal act when conception is possible. This is deliberately frustrating its natural power. You have full knowledge of the times in which the woman is likely to get pregnant and intend to only use the times when it's not likely or possible? Is this really not clear to you? Pope Pius XII clearly contradicts CC in his SPEECH to midwives even though he clearly says CC's contents are to remain valid always.


                                            

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I'm not sure why you should act as though rhythm/NFP (as taught by Pius XII) is obviously at odds with CC.  The teaching enjoys the approval of the Holy Office under both Pius IX and Leo XIII, not to mention plenty of theologians in the nineteenth and twentieth century, including those who take CC to reference and approve of it, distinguishing between intrinsically contra natura acts (birth control devices and the like) and rhythm or NFP.  If it's wrong, fine, but it's not obviously so if much more learned men then us can arrive at the conclusion they've arrived at.
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Anyways, is the following a fair representation of your argument, in logical form:
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(Major Premise 1) Contraceptive acts are intrinsically against nature
(Minor Premise 1) NFP (i.e., the reservation of the marital act to sterile periods for a grave reason) is contraceptive
(Minor Premise 2) But a thing which is intrinsically against nature can never be licit, no matter the situation
Ergo, reserving the marital act to sterile periods is sinful as such
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?
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I understand that you (given the quote you gave from CC) would not assign guilt of acting contrary to the natural order to a couple who was permanently infertile.  I don't think the syllogism covers that part, so maybe you'd like to re-word it a little so that it's clear that only those who are normally fertile sin by observing the periods of sterility (if that is, in fact, your position-- I'd be curious to know what difference it makes).

I rather think CC supports what I'm saying, rather than what you're saying. Pius XII read it, even cites it in his letter to the midwives (in which he teaches that it is lawful for couples to reserve the marital act to sterile periods for a grave reason). Surely you don't think you understand it better?

Yeah, Pius XII mentioned CC but he left out a crucial piece of it.  Pius XII cited CC in support of the principle that it's sinful to frustrated the inherent potential of the martial act (aka via birth control, onanism, etc.) but then conveniently ignored the OTHER principle taught by Pius XI, namely, that it's sinful to subordinate the primary end of marital relations to the secondary.  And when one is trying to prevent the primary ends in order to enjoy the secondary only, that is CLEARLY AND DIRECTLY in violation of the Pius XI CC teaching ... a principle that Pius XII COMPLETELY IGNORED.  Epic fail by Pius XII.  And Pius XII's fruits have been evident now since his death, as he opened the floodgates for the contraceptive mentality, the notion of limiting children, etc.  Similarly, Pius XII opened the floodgates to liturgical experimentation and ecuмenical dialogues.  No St. Pius X was he.  Pius XII also appointed the vast majority of the modernist bishops who would bring us the glories of Vatican II.

Anyways, is the following a fair representation of your argument, in logical form:
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(Major Premise 1) Contraceptive acts are intrinsically against nature
(Minor Premise 1) NFP (i.e., the reservation of the marital act to sterile periods for a grave reason) is contraceptive
(Minor Premise 2) But a thing which is intrinsically against nature can never be licit, no matter the situation
Ergo, reserving the marital act to sterile periods is sinful as such
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Has nothing to do with it.  It's the teaching of CC that the primary end of marital relations can never be subordinated to the secondary ... which Pius XII completely ignored, citing only the section on the inherent potential (natural power) of the act.

klasG4e,

No one is defending the indiscriminate use of NFP found and taught in the Novus Ordo.  The only question is about Pius XII's teaching, and even those who say he was wrong understand that he stipulated the use of NFP on a grave reason.