Mith, if a couple practices NFP "naturally" are you arguing that Pius XI said that the ends are ordered, so there is no intrinsic sin? Based on your comments in reply 32, it seems you are. And I would agree.
You've got it in a nutshell. What Pope Pius actually says-- if you compare the Latin to the traditional English translation found in pre-conciliar Denzinger and used by the theologians-- is that if
the act is performed naturally, then
the ends are duly ordered. The two go hand in hand with the one following from the other, they're not two separate conditions like Ladislaus is contending (but in his defense, I think he's basing his reading off of a translation which could be read that way, he didn't make it up out of whole cloth).
However, if a couple is practicing NFP to avoid children, without grave reason, then EXTRINSICALLY, they are sinning. Doesn't matter if their intrinsic relations are moral; their external motives are immoral.
If they lack a sufficient reason to use it, then they sin, just like if you lack a sufficient reason to miss mass, you sin (this is the common thread in all positive precepts: when you're commanded to do
something, you sin in not doing it unless you have a sufficient reason not to).
The whole reason I was talking about intrinsic/extrinsic was to help illustrate that whatever
periodic continence is, it isn't
forbidden by Pius XI's Casti Conubii
, since Casti Conubii
only concerns itself with what is intrinsic to the act (i.e., onanism and contraception proper). This is a point which is less relevant at this stage of the conversation (at least between you and I, since we seem to agree on it) but which was relevant earlier when at least to me it sounded as though some people were arguing that periodic continence is condemned in Casti Conubii
. It isn't. Which doesn't (by itself) prove that its lawful, but disarms the most common argument that it's unlawful
, for sure.