I think that the Address to Midwives is not nearly as rigoristic as it is being represented in this thread.
From the Address:
“Now, on married couples, who make use of the specific act of their state, nature and the Creator impose the function of providing for the preservation of mankind.”
I was earlier googling the minimum average number of births necessary to sustain the population (i.e. provide for “the preservation of mankind”), and Google informed me that in developed countries, you need an average of 2.1 births per woman while in developing countries you may need around 3.4 because of the higher mortality rate. Now, allowing for the fact that not every woman is able or willing to have children, the women who do have children will need to have more than 2.1 or 3.4 each, but that doesn’t get us to more than 3-4 for a developed country or 4-6 for a developing country. This is very approximate (a math person would need to do the actual calculations), but it would appear that “providing for the preservation of mankind” purely in terms of having babies does not necessarily need to consume every healthy, conscientious married woman’s entire reproductive life.
On the other hand, “providing for the preservation of mankind” might very well require a very substantial investment of time and resources on the part of parents, if “the preservation of mankind” is understood more broadly to include the upbringing and education of morally upright offspring who will grow up to serve their fellow man.
“The individual and society, the people and the State, the Church itself, depend for their existence, in the order established by God, on fruitful marriages.”
As opposed to marriages with no offspring at all.
“Serious motives, such as those which not rarely arise from medical, eugenic, economic and social so-called “indications,” may exempt husband and wife from the obligatory, positive debt for a long period or even for the entire period of matrimonial life.”
My husband points out that “medical, eugenic, economic and social so-called “indications”” are described here as examples of “Serious motives,” and that those four items are not intended to be an exhaustive list of “serious motives”.
I would add that that “serious motives” might well include Rau’s case of wanting to contribute in some other way than reproduction to general welfare. I also note that “medical, eugenic, economic and social so-called “indications”” cover a lot of ground, particularly “economic” and “social.” There’s definitely room in those last two for “Mom and Dad need to use NFP because Mom’s got to work so the kids can go to Catholic school and graduate college with no debt so that they can get married and have kids themselves at a reasonable age.” (Student loans have lately been very harmful with regard to slowing down family formation among the younger generation.)
“If, however, according to a reasonable and equitable judgment, there are no such grave reasons either personal or deriving from exterior circumstances, the will to avoid the fecundity of their union, while continuing to satisfy to the full their sensuality, can only be the result of a false appreciation of life and of motives foreign to sound ethical principles.”
It’s not clear whether the pope here means couples who want no children at all or couples who already have children. This may in fact be primarily addressed to couples who want no children at all, ever.
I forget if this has been posted in this thread, but my husband directs me to Simcha Fisher’s “Why doesn’t the Church just make a list?”
patheos.com/blogs/simchafisher/2011/03/23/why-doesnt-the-church-just-make-a-list/
Here’s the first paragraph of Simcha Fisher’s piece:
“When Catholics talk about NFP, someone always asks rather plaintively why the Church doesn’t just clear up all the confusion about what does and does not constitute a legitimate reason to avoid a pregnancy. Why not just make a list: on the right, good reasons for postponing a pregnancy; on the left, bad reasons?”
My husband mentions that “serious” in ethical discussions doesn’t necessarily mean anything dire, but just means appropriate and proportionate, given what is at stake.