#1) subjugated is the wrong word (it's subordinated)
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If you're talking about the language of
Casti Conubii, "subordinated" appears in the Pieran Press compilation of papal encyclicals (edited by Mrs. Curan, I believe, circa 1990). The passage you're referring to is probably this one, and this translation:
[Sterile relations are intrinsically lawful because] in matrimony as well as in the use of the matrimonial rights there are also secondary ends, such as mutual aid, the cultivating of mutual love, and the quieting of concupiscence which husband and wife are not forbidden to consider so long as they are subordinated to the primary end and so long as the intrinsic nature of the act is preserved. (CC §59, link to Pieran Press translation)
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It sounds as though you are reading this as though subordination of ends is distinct from the preservation of the intrinsic nature of the act. However, this translation, while not awful, suffers when compared to the original Latin:
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...dummodo salva semper sit intrinseca illius actus natura ideoque eius ad primarium finem debita ordinatio (AAS 22, 539)
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A closer literal translation is what we find in Defararri in Denzinger, which is what preconciliar theologians relied on. The difference is subtle but significant:
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[Sterile relations are intrinsically lawful because] in matrimony itself, as in the practice of the conjugal right, secondary ends are also considered, such as mutual aid, the cultivation of mutual love, and the quieting of concupiscence, which spouses are by no means forbidden to attempt, provided the intrinsic nature of that act is preserved, and so its due ordering is towards its primary end. (CC §59, Denzinger translation)
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Neither the Latin nor the commonly used English translation makes the distinction between subordination and the preservation of the marital act's nature; rather,
since the intrinsic nature of the act is preserved, the ends
are duly ordered. If there is doubt on this point, consult Fr. Vermeersch who ghost-wrote
Casti Conubii:
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As long as the act takes place normally it remains objectively directed toward its primary end, which is generation; and since, according to the maxim that the purpose of the law is not within the matter of the law (finis legis non cadit sub legem), there is no obligation, while observing the law, to intend the end for which it was promulgated, it follows that the act is not necessarily vitiated by deliberately choosing a certain time with the intention of avoiding conception. (What is Marriage? A Catechism arranged According to the Encyclical Casti Connubii, 1932, p. 44, emphasis added)
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Barely two years after he wrote
Casti Conubii, Pope Pius XI affirmed the (1880) Holy Office rulings of Pope Leo XIII affirming the morality of periodic continence. This would be a very curious act of approval if he meant what you think he means.
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Now, of course the primary ends must be subordinated to the secondary ends-- we agree on this. My point is that
Casti Conubii regards this subordination as manifest when the act occurs naturally. There is no distinction to be had between the intrinsic preservation of the act and the ordering of ends. They are one and the same. If the ends are properly ordered, it means the act is preserved, and if the act is preserved, it means the ends are ordered.
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In deliberate "periodic" abstinence, the formal intent is to enjoy the secondary ends of marital relations while precluding the primary. Consequently, the secondary ends of marriage become the primary end.
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I think you are skipping over the crucial distinction between intrinsic and extrinsic.
Casti Conubii, when it teaches on marital relations, concerns itself very squarely with what is intrinsic to the act. Motives, intentions, and so forth are all extrinsic. Even if one is motivated insufficiently (for lawful use of periodic continence), the sin committed is not one against nature. That would be like saying if two couples had relations during fertile periods but one of them didn't want anymore children, that person sins against nature. I'm sure you realize that would be a silly thing to argue. Intentions, even if deplorable, have no bearing on intrinsics, nor could they. As to your comment about gratuitous assertions viz. periodic continence not being contraception, the assertions have not been gratuitous. Many reasons have been given.
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