Anima Christi:
There is still a chance you may conceive using a condom or being on the pill or other forms of birth control. So that is irrelevant.
I have been struggling with the morality of NFP too and I don’t see how something can be OK just because it’s “natural”.
This is a bit difficult to understand, and I struggled with it myself until a particular explanation made sense to me. I’ll try my best to present it here.
The question of the morality of ABC (artificial birth control) vs. NFP should be boiled down to the direct actions of the participants. In the case of ABC, the couple (or one member) is acting specifically to block the normal fertility of the sexual act they are in, or are envisioning. Once doing that, they continue with intercourse. In this case, they are envisioning a life that could result from their actual union at that time and acting specifically to stop that life from being created. The intercourse itself is not immorral – it is the action that deliberately removes natural fertility from the act that is immorral. Thus, with the use of ABC, there is an immorral act involved.
In the case of a couple practicing NFP, there is no act to hinder or block natural fertility while continuing to have intercourse. Rather, the couple does nothing at all – abstinence. There is no action by either member that can be judged to be moral or immorral.
Note that the use of NFP is
NOT considered a virtuous act (a moral good), it is simply morally neutral.
Thus, when serious reasons exist, the use of morally neutral NFP is allowed because it is not morally wrong, as ABCs are.
When looked at in this way, it can be understood why it can be morally licit to use medications or treatments for serious medical reasons that also happen to hinder or block fertility. Take a patient undergoing chemotherapy, for instance. In that case, the treatment also hinders fertility, but the treatment itself is not being done in order to thwart a life that God could naturally bring with a sexual union. It is, rather, an undesired side-effect. Thus the sexual union is still good and holy (when done out of love and within the marriage covenant), and is not accompanied by a deliberate morally evil act to thwart life.
This perspective also allows for the understanding that NFP, being morally neutral, can be practiced for morally wrong reasons (a selfish desire to be free of children, for instance). In that case it is the selfish reasons that are sinful, not NFP or the sexual act itself.
I learned this from a highly regarded monseignor (who was an adult convert from protestantism, BTW) who teaches medical ethics. I hope that I have not misrepresented what he taught me.
I hope this makes sense to you. I know I am not always the best at explaining things, so please ask for clarification if you feel the need.
Peace,
javelin