Patricia and Marcus are a married couple. Each day, they prudently decide whether or not to engage in marital union. To make that decision, they weigh all the relevant factors they can, gathering information relevant to the decision ahead of time when appropriate. They do nothing to intentionally decrease the fertility of their bodies, and when they decide to unite maritally, they do nothing to intentionally decrease the likelihood of conception.
What I have described is not a contracepting couple. What may not be immediately obvious is that I have described a couple practicing Natural Family Planning (NFP). One way to look at NFP is precisely as the gathering of some of the information relevant to a prudential decision whether or not to engage in marital union at a given time, and then making the decision in part in light of that information. For, plainly, the probability of conception is information relevant to a prudent decision whether or not to engage in marital relations. The way the information is relevant will depend on other information. If, for instance, the couple is suffering from severe financial distress, the learning that the probability of conception is high will make the decision to engage in marital relations less prudent than these relations would be if the probability were low. On the other hand, if the couple is in good personal, financial and relational health, learning that the probability of conception is high will make the decision to engage in marital relations more even more prudent than it would be if if the probability were low. ("Prudence", here, is Aristotelian phronêsis, of course.). It is clear, by the way, how NFP is useful not just to the couple for whom conception would be imprudent, but also to the couple trying to conceive.
Information relevant to the decision whether to engage in marital relations includes how tired the two persons are, what privacy is available to them, what their feelings about each other are, what potentially time-consuming duties they may have, whether there are any relevant medical considerations, and so on, all enter into the decision. That this kind of information needs to enter into the decision is clear and uncontroversial. But likewise, information about further consequences of an action is relevant to deciding whether to engage in the action or not, and hence fertility information is likewise relevant.
Seen in this way, it is clear that one cannot object in principle to every instance of NFP without being committed to at leat one of two implausible views:
- It is wrong for a couple to engage in sexual relations when the likelihood of conception is low.
- It is wrong for a couple to refrain from engaging in sexual relations because the likelihood of conception is high.
Objection 1: Although (1) is clearly innocent, what the couple is doing is not just deciding to engage in sexual relations when the likelihood of conception is low, but because the likelihood of conception is low.
Response: Consider the sense of this "because". It is not so much that the low probability of conception is their reason for having sex--after all, there are many uncontroversial activities other than sex that have much lower probability of conception, say sharing ice cream. Rather, the low probability of conception may imply the absence of a defeater to their independent reason to unite maritally, this defeater being the bad consequences of conception in their special situation (e.g., one of financial hardship). When deciding whether to engage in any action that isn't an all-things-considered duty, we need to consider potential defeaters. So if (1) and (2) are innocent, it must also be innocent to take into account the presence or absence of defeaters, since one must always do that in the case of a decision whether to engage in marital relations.
Objection 2: Over and beyond the daily decision between engaging and not engaging in marital union, there is the "plan of action as a whole", which in the case of a couple who uses NFP to avoid conception involves the timing of intercourse so as to avoid conception, and it is this plan of action as a whole that is analogous to contraception.
Response: There need not be any such overarching plan of action. When I described Patricia and Marcus, I did not attribute any such plan to them. Rather, it is possible that the couple is deciding, on a day to day basis, whether sexual union on that day is prudent in light of all the relevant information they have gathered. Granted, there may be an on-going condition (say, financial) which renders sexual union imprudent when it has a non-low probability of conception, and they need not think through the details of that condition each day, but can simply be on the lookout for when, if ever, the condition comes to an end. But it is quite possible to decide day after day on the same grounds--and yet for it to be a genuine decision, though it may become somewhat habitual. The fact that it is a genuine decision is evidenced by the data that at times NFP couples do decide to have sexual relations even when it is imprudent to do so, apparently without a significantly prudentially relevant change in circumstances (this is probably the main source of pregnancies among couples using NFP to avoid conception).
That said, one can imagine a couple who instead of deciding on a daily basis decides that over the next six months they will try to avoid conception. Still, it seems to me that they are likely to be making a daily decision whether they ought to keep to their earlier resolution. That said, I do not need to defend the actions of such a couple. To argue that NFP is morally permissible, I need to argue that there is some set of circumstances and motives under which NFP is permissible. It is false that NFP is permissible under all circumstances and with all possible sets of motives, and I actually suspect that a married couple's decision to refrain from conception ahead of time, without reference to changing circumstances, is morally problematic. Note that it is different to decide once for six months not to conceive, and another simply to expect that over the next six months one will each day have all-things-considered reason to avoid conception, but to still be making the decisions on a daily basis, since after all the reason to avoid conception might go away.
Summary: One way for NFP to be practiced, and it is this one way that I am defending here, is to think of it as the gathering of certain information relevant for the decision (I talk of "daily", but that is just a convenience--it could in principle be hourly) whether or not to engage in marital union at a given time. The information in question is fertility information. The prudent couple, of course, will also gather other information, and take that into account. Seen this way, NFP is not only clearly morally permissible, both in light of reason and of the Catholic tradition, but is positively virtuous, involving the virtue of prudence, as well as, when abstinence is called for, the virtue of self-control. What is the alternative? To fail to gather relevant information?