Down yonder, a reader writes:
Please help me to better understand this issue. I don’t need convincing on the sinfulness of contraception. I need to better understand the relationship to NFP, which the Church allows.
In your initial post, you state: "The Church has always taught the intrinsic evil of contraception, that is, of every marital act intentionally rendered unfruitful". But doesn’t this occur in NFP? Isn’t the couple planning their sexual relations around a time that it is almost certain to be unfruitful? Aren’t they divorcing the pleasure of the act from its openess to life? Isn’t their intent the same as the couple who uses artificial contraception; only the "means" being different?
I do understand that God did not design us so that every sexual act produces children. Of course, NFP takes advantage of this. I also know that there is always a chance of new life, even when practicing NFP properly. But there is also that chance with artificial contraception. It is not 100% effective.
Help me understand the distinction here. My logic must be flawed, because I know the thinkers in the Church are a lot smarter than I am!
You have put your finger on the decisive fact in this: "God did not design us so that every sexual act produces children. . . . NFP takes advantage of this."
In many mammalian species, God designed things so that the males are sexually receptive all the time, while females are only sexually receptive in proximity to their fertile period. Thus such species tend to only engage in sexual activity in proximity to fertility.
But God designed humans different. In our species both genders are sexually receptive in general, not just when a woman is fertile (though there appears to be an increase of sexual receptivity at that time). The result is that humans engage in sexual activity even though most of the time it has no chance of resulting in procreation.
The fact that we cannot, in the case of any given act of marital congress, utterly rule out the possibility of procreation, this says more about the limitations of our predictive ability than anything else. If we had better knowledge of what was happening in a woman’s body (as we well may one day), we would be able to say with certainty that there will be no procreation from a particular act of union.
Even so, we can in the case of a great many couples (those where the husband or the wife or both are infertile, either due to age or some other cause) say with certainty that there will be no procreation as the result of an act of union. Yet the Church has never expected such couples not to have marital congress in such cases.
The issue thus is not whether there is a chance of there being a conception. It is a red herring to suggest that NFP is okay because it is unreliable (always some chance of conception) while contraception is wrong because it is reliable (no chance of conception). In reality, many cases where NFP are used have no objective chance of resulting in conception (we just often can’t identify those cases up front), and in many cases contraceptive sex does have the chance of resulting in conception.
The question is not whether a particular act has the potential for fertility. The question is whether you are doing anything to render the act deliberately infertile. This is what the document I quoted refers to when it speaks of "marital act intentionally rendered unfruitful" (emphasis added).
In the case of an act of NFP the couple is not doing anything to make themselves infertile. They are simply having marital congress when nature makes them infertile.
Similarly, a couple with permanent infertility (due to age or some other cause) is not deliberately making themselves infertile each time they have marital congress. As with the first couple, they are simply having marital congress when they already are infertile.
But when a couple performs a specific act to make themselves infertile (having surgery, taking a chemical, employing a device) then that act is deliberately frustrates God’s design for human sexuality and so is sinful.
(Note the emphasis on "that act." The sinfulness does not extend to future acts of marital congress if the couple repents as they are no longer affirming by their will the act of rendering themselves infertile.)
The issue thus is not whether any given act of union has a chance of producing a child. Nor is the issue whether one ever has children (that is an important issue, but a different one than this). The issue is whether you are doing something to deliberately frustrate the fertility of a particular sexual act.

