The underlying idea is this: the healthy, normal, human body, complete in every detail: God demonstrates very, very often that that's what He wants for us.
God's design for us at the outset, at Creation, was very good (that was the First Reading at Mass today!). That's why real medicine is legitimate: because legitimate medicine has the aim of restoring the body, as far as possible, to its normal, healthy condition.
Contraception (to impair the body with a drug, device, or surgery, to disable its power and design)) treats the good, fertile, womanly body as if it's got a design defect. Something that's bad. This is an untruth, and rather an aspersion cast upon the Creator, as if to say, "You made me, and all other healthy normal women, wrong, wrong, seriously wrong: but AHA! I'll nullify it."
Fertility isn't a design defect. It's a design feature. And the Designer said so.
So drugs, devices and surgery are OK if they are directed toward restoring, healing, curing, returning the body back to normal function. BUT...
Think of hormonal drugging & surgery to change one's ... er, what do they call it? gender? ... It has a whole lot in common with contraception: using drugs, devices, and surgery to change one's sexuality by making oneself a procreative neuter.
If Cousin Jane "put herself in some semblance of the biological position of" Nephew Gary, it wouldn't conform to any revelation of the Will of God that I know of.
Um... Book of Neuteronomy?
(I'm not trying to offend anyone's sincere faith. Certainly not your, my dear HiTech. I'm just applying the principle to discover the implications.)
(And the priciple, "It's OK to chemically/surgically impair your body to alter or disable your sexuality," is wrong.) I don't see how the practice of medicine can ethically intentionally cause a disorder, rather than cure it. Contraception, like sex-change surgery, causes a disorder, wether it's temporary or permanent. I would have to call that a disordered medical practice.
I would welcome a further discussion, if you want.
Um.
Otherwise, I'm outside to plant more garlic if the weather holds. :o)
I respect your point of view and as I said it has some advocates in the evangelical community as well. By means of medications or things that have the action of medications, many perfectly natural things can be deferred to serve one or another purpose. Drinking coffee can defer sleep so you can study or work more. Swallowing pills containing certain hormones can defer ovulation so that you will conceive children when your family is in a position to support them. (The immature eggs remain there in the ovaries, they do not die, but also do not mature and come out until the hormones are stopped.) Some are horrified at the thought of either or both, even though intercourse could also be timed such that the possibility of pregnancy is mostly evaded, and hardly anybody complains that THIS is evil.
Anyhow — surely procreation is one of the biggest mysteries of which mankind is aware and some very understandably do not want to tread on that holy ground at all.