Hmm. You make an interesting moral point. Let's push this to the absurd. If I wanted to kill you, the means I might use are not 100% effective. You could still live if I stabbed you or shot you or poisoned you. Does that lessen the moral culpability on my behalf? No. And why not? Because no matter what eventually transpired, my *intent* was to kill you.
So I'd say intent is everything here. Suppose a guy wore tight underwear not realizing that was making him (in his case) 100% infertile. That wouldn't be a sin. But the person who used a condom at 50% effectiveness could be more in sin territory because he was actively trying to thwart conception and he knew it.
NFP is not immoral because all a couple is doing is not having sex during fertile periods. Nothing wrong with that. But there is something wrong with having sex and THEN blocking conception. It's trying to eat your cake and have it too.
However, and just to complicate matters, I and most other traditional Catholics would seriously question the morality of someone who was slavishly devoted to NFP to avoid pregnancy *and had no good reason to.* Just because it's allowed doesn't mean you should use it all the time.
Actually, I thought this was a rather clever way of expressing what I was trying to get at :) Do you mind if I use this the next time I am discussing the topic with my religious friends?
I probably picked it up from someone else...(I think G. Gordon Liddy has said similar things). So feel free!
Your point on intent is well taken. But I'm still not quite sure why NFP gets a free pass, so to speak. I hope I'm not pushing your patience past the breaking point, but I wonder if you might clarify it for me.
Maybe an example would illustrate my confusion. Suppose a couple has some valid reason to avoid conception for a few months. Obviously, they could simply choose not to have sex for the entire time and avoid any moral problems. But the couple doesn't like the idea of having to go without sex for so long.
So the couple considers two other options that will let them have sex without having to worry about conceiving a child. One is to monitor the wife's cycle and plan their encounters for her infertile periods, when conception is very unlikely to happen. The other is to use some form of contraception (just for a few months), which also makes it unlikely that conception will result from any of their encounters. The couple acknowledges that a child may still be conceived under either option, and are ready and willing to accept any children conceived during the use of NFP or contraception.
It seems that under both options, the parents are trying to enjoy the fun of sex while actively reducing the chances of conception for a period of time. With NFP the couple is not actively *blocking* conception. But even though the means differ, the *intent* is the same. Under both scenarios, the couple wants to have their cake and eat it too.
So why is the NFP option ok? (Again, assuming that it is just used for a few months and there's a valid reason to avoid pregancy.)