You'll have to forgive me a bit, today; I've been battling a stupid migraine all day, and am now pressed for time as I try to get things ready for Bookgirl's birthday tomorrow.
While I haven't had time to enter back into the comments regarding the Church's teaching against contraception in the comments below this post, I've been reading them. I still think that there is, for many people, a fundamental misunderstanding about contraception that comes from not fully understanding the Church's teachings regarding marriage and the family.
I'm not a moral theologian, and my understanding of these matters is simply that of a Catholic lay woman. And today probably isn't the best day for me to be delving into matters so deep--but I wanted just to get the conversation going, in the hopes that better-trained and more focused Catholics will chime in.
In the first place, one of the phrases the Church uses both about marriage generally and about the marital embrace specifically is that it involves the total gift of self to other. That, essentially, is what love is; and marital love has a physical dimension proper to it exclusively.
What is a total gift of self to other? It is saying, in the marriage covenant, that I no longer belong solely to myself, but also to someone else, and he belongs no longer solely to himself, but also to me. The marital embrace is both the sign and the consummation of this unity of self with other, and in its highest expression, in the children who result from the embrace, who are truly flesh and blood of both husband and wife equally; thus, the children are the living signs of their parents' permanent and committed love.
Now, it is the sad reality of our fallen world that children are born outside this union of permanent and committed love. This has all sorts of evils for the children, who may very well be deprived of their most essential birthright: the right to be loved, raised, and cared for by their own parents. Children, who are wholly innocent, are owed this, and they deserve it; adults who by their behavior deprive them of it act very badly indeed.
Given that, you would think that the Church would almost condone contraception outside marriage--but she does not, for excellent reasons. Primary among these reasons is that sex outside of marriage, contraceptive or not, is a lie. It cannot involve a total gift, when each person is holding back from the other their public and binding committment as well as their fertility; it is not yet promised to be permanent, even if by God's grace the couple sees their error, repents, and then enters into such a permanent union; and it is not committed by its very definition. Any children born into this pseudo-union are in a precarious situation, and though it may be hoped that their parents will do the right thing as regards their children there is no guarantee that they will, and plenty of statistical evidence suggesting that they will not.
But what about contraception within marriage? Why can that not be allowed?
Again, because contraception itself renders sex, even inside marriage, a lie. The husband "says" to his wife with the language of his body, I give myself totally to you--except for my ability to give you children, and I accept the gift of your total self--except for your ability to have children, and the wife "says" the same thing back to him, allowing for the change in pronouns. But there can be no total gift when a vital aspect of that gift is being denied; the marital embrace becomes not unifying, but isolating; the couple are not drawn closer together, but pushed farther apart.
Interestingly, statistics from the Natural Family Planning group show that married couples who use NFP have a less than 5% divorce rate (which is still too high, of course) compared to a national divorce rate of 50%. I'd like to see a study done in which those who use no family planning at all are included with those who use natural means, and those who use contraception are included with those who have been surgically sterilized--because I'd be willing to bet that the divorce rate of the former group would also be a fraction of the divorce rate of the latter.
Sex is a sacred gift, but it is not a gift which belongs to one person, to use with as many others over the course of his life as he sees fit. Rather, it is a gift that is only properly used when it is given to one other person exclusively within the context of a permanent, committed marriage. Any other use of it is gravely unjust to the person himself, to those with whom he "uses" this gift, and to any children born deprived of the loving relationship with their parents which they are owed by virtue of their humanity.