An Analogy with Agriculture: NFP’s Causal Structure

An additional example of acts with different causal structures which have similar outcomes can help to elucidate the distinction between preventing conception and occasioning the failure of conception.

Trees have their own natural intention toward growth, like gametes have toward procreative union. If a farmer were to plant a tree in good soil found in a climate that he knew was ill-suited to its growth (such as not enough sunlight or rain) so that the tree would fail to grow due to the lack of good weather, we would not say that the farmer prevented its growth so much as we would say the tree failed to grow because of the bad climate. We would also say that its lack of growth was intentionally occasioned by the farmer. Suppose further that his goal was simply to enjoy planting trees but did not desire them ever to grow, and so he repeated this many times, always avoiding planting trees in good weather, until one day he knew it was the right time to plant a tree that would grow. This is like NFP, which disposes the sexual act to fail to achieve what nature intends by using the condition of infertility until such a time as it seems right to attempt conception by using marriage during a known fertile time.

On the other hand, if the farmer planted the same tree in good soil found in a climate conducive to growth but then covered the tree with a tarp so that the necessary amount of sunlight or water could not reach it, or he poured acid on the tree so that it became sick and therefore could not grow, we would say that the farmer prevented the growth of the tree; it is not merely that the tree failed to grow, the farmer intervened in the system in which the tree is naturally supposed to grow so that it would be unable to do so, instead of an internal principle of the tree failing to achieve its purpose merely due to something inside of the ecosystem not being conducive thereto. This is analogous to contraception, which is a positive intervention that prevents the success of what nature intends for the gametes in the sexual act.

The point of this analogy is to help illumine the difference between preventing success and intentionally occasioning failure. Of course, trees can morally be covered with tarps, poisoned with acid, planted in cement, or even cut down. The moral difference with procreation is that humans are not set over other humans or the means by which they are generated to the extent we are set over trees and their growth.